Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Joachim Franek]

On Sunday 04 March 2012 20:29:02 Jon Elson wrote:
> >   
> Do not try to control FET dead-time with software.  Very simple
> RC circuits with an added diode to reduce the R in one direction
> have been used for years.  The R delays turn-on, the diode
> causes fast turn-off.
> 
> Jon

Thanks for the hint.
As an exercise I wrote this component.

Joachim 

component delay_rising_edge "jf's delay for bldc outputs: delay rising edges";

//inputs
pin in bit inh;
pin in bit inl;
pin in bit pwml; //for pwm lower fet's
pin in bit pwmh; //for pwm upper fet's

//outputs
pin out bit outh "High-side driver for phase";
pin out bit outl "Low-side driver for phase";

param rw unsigned delaycount=3;

option data dre_data;
author "Joachim Franek";

function _ nofp "delays rising input edges to avoid cross current in the power 
stage of a bldc/pmsm driver";
license "GPL";

variable int counth=0;
variable int countl=0;

;;

typedef struct {
int lasth;
int lastl;
} dre_data;

FUNCTION(_)
{ 
  int newl;
  int newh;
int temph=0,templ=0;

newl = inl;
newh = inh;

  if ((newl == data.lastl) && (newh == data.lasth))  //low and high the 
same as last cycle
{
temph = newh; //do nothing
templ = newl;
  } 
else//low or high uneven
{
if ((newl == 1) || (newh == 1)) //rising edge low or 
high: delay the rising edge
{
if (newl == 1) //rising edge low: delay low
{
temph = newh; 
countl=delaycount;
}
if (newh == 1) //rising edge high: delay high
{
templ = newl;
counth=delaycount;
}
}
else
//falling edge low or high
{
  temph = newh; //do nothing
templ = newl;
}
  }

if (counth>0)
{
temph = 0;
counth--;
}

if (countl>0)
{
templ = 0;
countl--;
}

if ((temph!=0) && (templ!=0)) //check min one is low
{
temph=0; templ=0;
}

if (pwml == 0) //pwm for lower fet's
{
templ=0;
}

if (pwmh == 0) //pwm for upper fet's
{
temph=0;
}

outh=temph; 
outl=templ; 

  data.lasth = newh;
  data.lastl = newl;
}

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Re: [Emc-users] IRAMS Plan

[Joachim Franek]

On Sunday 04 March 2012 10:34:32 Joachim Franek wrote:
> 
> 2. Add 6 and gates to stop motor commutation in case of to high DC voltage.
> 

Search the net for "IGBT protection" and find for example:
ir2137igbt.pdf: IGBT Protection for AC and BLDC Motor Drives
fuji_igbt_application_manual(REH984).pdf: See chapter 5.


Joachim 

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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[charles green]

i'm in an apt, so i'd have to luck out and find to wall strings on different 
legs for dopple volts.


--- On Thu, 3/8/12, Kirk Wallace  wrote:

> From: Kirk Wallace 
> Subject: Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11
> To: "Enhanced Machine Controller (EMC)" 
> Date: Thursday, March 8, 2012, 11:41 AM
> On Thu, 2012-03-08 at 03:19 -0800,
> charles green wrote:
> > it is a cost sensitive application, as always, and
> limited to single
> > 115v phase mains supply.  there are the sherline
> spindles/motors with
> > decent speed controls, but sherline stuff is kinda
> spendy.  i dont
> > recall seeing any retail vfd pages, but i'm thinking in
> the many H$ to
> > a K$ or so for a drive, and the smaller power motors
> i've come across
> > replacing are a few hundred on their own.  in
> contrast, a bench
> > grinder from a home store or walmart can go as low as
> $40.  ..hmm.  i
> > wonder how hard it would be to rewind one?
> 
> In the US, 240 Volts AC is available from a dryer outlet and
> 240 VAC
> usually runs to the kitchen for an electric oven, so there
> may be a way
> to get 240 to where you need it that isn't too hard to rig
> up. I have a
> 40 Amp dryer type extension cord that I plug my machines
> into. It's not
> very convenient because I can only run one machine at a
> time, but it
> works for now. 
> 
> I also have a large transformer that can boost 120 VAC to
> 240 VAC. With
> 120 VAC outlets rated for 15 Amps max., I can only get 7
> Amps of 240 VAC
> from the transformer, but this is enough for testing most of
> my VFD's.
> This one is similar:
> http://www.ebay.com/itm/290647166101 
> 
> eBay has some cheap VFD's:
> http://www.ebay.com/itm/290580719222
> 
> Motors are a problem, but this might work:
> http://www.ebay.com/itm/170795747608 
> 
> it runs on 120 VAC three phase, so a VFD would need to be
> set up to
> limit the output voltage, but that's easy to do.
> 
> DC treadmill motors work well with KBIC type speed
> controllers but these
> can be harder to find and can be more expensive.
> 
> I tend to look at what I have on hand or what I can find on
> trash day or
> in dumpsters before I start looking at new stuff.
> 
> -- 
> Kirk Wallace
> http://www.wallacecompany.com/machine_shop/
> http://www.wallacecompany.com/E45/index.html
> California, USA
> 
> 
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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Stephen Dubovsky]

Up to ~1.5hp you can buy 115v input VFDs that output 220v.  I think they
just use voltage doublers in their rectifier stage and 2x the capacitance.

FWIW, these DON'T work well in a (properly wired) garage.  120V outlets in
a garage are supposed to all be GFCI protected.  Motor frame leakage
currents will trip the GFCI when using a VFD:(  220V outlets are not GFCI
protected.

SMD

On Thu, Mar 8, 2012 at 2:41 PM, Kirk Wallace wrote:

> On Thu, 2012-03-08 at 03:19 -0800, charles green wrote:
> > it is a cost sensitive application, as always, and limited to single
> > 115v phase mains supply.
>
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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Kirk Wallace]

On Thu, 2012-03-08 at 03:19 -0800, charles green wrote:
> it is a cost sensitive application, as always, and limited to single
> 115v phase mains supply.  there are the sherline spindles/motors with
> decent speed controls, but sherline stuff is kinda spendy.  i dont
> recall seeing any retail vfd pages, but i'm thinking in the many H$ to
> a K$ or so for a drive, and the smaller power motors i've come across
> replacing are a few hundred on their own.  in contrast, a bench
> grinder from a home store or walmart can go as low as $40.  ..hmm.  i
> wonder how hard it would be to rewind one?

In the US, 240 Volts AC is available from a dryer outlet and 240 VAC
usually runs to the kitchen for an electric oven, so there may be a way
to get 240 to where you need it that isn't too hard to rig up. I have a
40 Amp dryer type extension cord that I plug my machines into. It's not
very convenient because I can only run one machine at a time, but it
works for now. 

I also have a large transformer that can boost 120 VAC to 240 VAC. With
120 VAC outlets rated for 15 Amps max., I can only get 7 Amps of 240 VAC
from the transformer, but this is enough for testing most of my VFD's.
This one is similar:
http://www.ebay.com/itm/290647166101 

eBay has some cheap VFD's:
http://www.ebay.com/itm/290580719222

Motors are a problem, but this might work:
http://www.ebay.com/itm/170795747608 

it runs on 120 VAC three phase, so a VFD would need to be set up to
limit the output voltage, but that's easy to do.

DC treadmill motors work well with KBIC type speed controllers but these
can be harder to find and can be more expensive.

I tend to look at what I have on hand or what I can find on trash day or
in dumpsters before I start looking at new stuff.

-- 
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA


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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Thomas Powderly]

Awallin,
those gate drive opto's from Shane Colton are sweet
and the MITER's blogs are great
I have to replace an ebike BLDC controller
maybe able to use orphaned Mitsubishi motors with his design
thanks
TomP

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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[charles green]

it is a cost sensitive application, as always, and limited to single 115v phase 
mains supply.  there are the sherline spindles/motors with decent speed 
controls, but sherline stuff is kinda spendy.  i dont recall seeing any retail 
vfd pages, but i'm thinking in the many H$ to a K$ or so for a drive, and the 
smaller power motors i've come across replacing are a few hundred on their own. 
 in contrast, a bench grinder from a home store or walmart can go as low as 
$40.  ..hmm.  i wonder how hard it would be to rewind one?

--- On Wed, 3/7/12, Jon Elson  wrote:

> From: Jon Elson 
> Subject: Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11
> To: "Enhanced Machine Controller (EMC)" 
> Date: Wednesday, March 7, 2012, 10:38 AM
> charles green wrote:
> > so the motor in, say, a small drill press or a _bench
> grinder_ is probably of the resistive start winding type?
> >   
> Yes, generally.  Some of these may be capacitor-start,
> however.  If it 
> has a big rounded lump
> on the side of the motor, then it is cap start.
> > it would be nice to turn the rpms on a bench grinder
> way down for final figuring of certain cutter edges, to
> reduce removal rate, reduce heat at the cutter edge, and
> reduce innaccuracy from vibrations.
> >   
> Well, get a 3-phase grinder and a VFD.  With the stock
> single-phase 
> motor, it can be done,
> but is very difficult.  There are 2-phase VFDs, or you
> could use a Scott 
> Tee to convert the
> 3-phase to 90 degree 2-phase.
> > brushed ac motors are easy to turn up and down, but
> have a large defect of set point compliance with any
> loading, especially at lower rpms.  (..and they are
> noisy.)
> >   
> Yes, you can use a closed-loop speed control, or convert the
> motor from 
> series to
> shunt with a controller.
> 
> Jon
> 
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Re: [Emc-users] IRAMS Plan

[Anders Wallin]

2012/3/6 Joachim Franek :
>
> FNB41060 - IGBT SMART PM,600V,10A
> < 10 Euro at Farnell

I think the IRAMS and this FNB41060 definitely 'solve' the H-bridge
part of the circuit. The challenge is to design current-sensing,
EMI-filtering, powersupplies, and optoisolation around the H-bridge.
I forgot to mention earlier this blog I have been reading which has a
lot of motor-control posts:
http://scolton.blogspot.com/

AW

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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Kirk Wallace]

On Wed, 2012-03-07 at 21:01 -0600, Jon Elson wrote:
... snip
> But, capacitor-RUN motors are made to have the start winding energized
> continuously.  If you had a VFD that was designed to produce two outputs
> with a 90 degree phase shift, you could run a capacitor-run motor from
> it just fine.  You would leave out the start and run capacitors and the
> starting switch, and let the VFD do all the work.
... snip

I have a similar setup but at lower voltage, but still a two phase
induction motor.
http://www.wallacecompany.com/E45/rotor_cam.html 

I may need to dust this project off and finally finish it.
-- 
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA


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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Jon Elson]

Greg Bernard wrote:
> Are you saying a single phase motor can be driven with 2 phase? How would 
> that be done and how would you control speed with such an arrangement?
>   
Almost all motors that run from single-phase mains are actually 2-phase 
motors.
The exception are the shaded-pole motors.  Other motors need a phase
rotation to start, and this is typically provided by a "start winding" which
is switched in to start the motor.  Now, the problem is the start 
winding was
designed for starting, and so is usually not made to handle the heat of 
continuous
operation.

But, capacitor-RUN motors are made to have the start winding energized
continuously.  If you had a VFD that was designed to produce two outputs
with a 90 degree phase shift, you could run a capacitor-run motor from
it just fine.  You would leave out the start and run capacitors and the
starting switch, and let the VFD do all the work.

Jon

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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Greg Bernard]

Are you saying a single phase motor can be driven with 2 phase? How would that 
be done and how would you control speed with such an arrangement?




>
> From: Jon Elson 
>To: Enhanced Machine Controller (EMC)  
>Sent: Wednesday, March 7, 2012 12:38 PM
>Subject: Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11
> 
>charles green wrote:
>> so the motor in, say, a small drill press or a _bench grinder_ is probably 
>> of the resistive start winding type?
>>  
>Yes, generally.  Some of these may be capacitor-start, however.  If it 
>has a big rounded lump
>on the side of the motor, then it is cap start.
>> it would be nice to turn the rpms on a bench grinder way down for final 
>> figuring of certain cutter edges, to reduce removal rate, reduce heat at the 
>> cutter edge, and reduce innaccuracy from vibrations.
>>  
>Well, get a 3-phase grinder and a VFD.  With the stock single-phase 
>motor, it can be done,
>but is very difficult.  There are 2-phase VFDs, or you could use a Scott 
>Tee to convert the
>3-phase to 90 degree 2-phase.
>> brushed ac motors are easy to turn up and down, but have a large defect of 
>> set point compliance with any loading, especially at lower rpms.  (..and 
>> they are noisy.)
>>  
>Yes, you can use a closed-loop speed control, or convert the motor from 
>series to
>shunt with a controller.
>
>Jon
>
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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Jon Elson]

charles green wrote:
> so the motor in, say, a small drill press or a _bench grinder_ is probably of 
> the resistive start winding type?
>   
Yes, generally.  Some of these may be capacitor-start, however.  If it 
has a big rounded lump
on the side of the motor, then it is cap start.
> it would be nice to turn the rpms on a bench grinder way down for final 
> figuring of certain cutter edges, to reduce removal rate, reduce heat at the 
> cutter edge, and reduce innaccuracy from vibrations.
>   
Well, get a 3-phase grinder and a VFD.  With the stock single-phase 
motor, it can be done,
but is very difficult.  There are 2-phase VFDs, or you could use a Scott 
Tee to convert the
3-phase to 90 degree 2-phase.
> brushed ac motors are easy to turn up and down, but have a large defect of 
> set point compliance with any loading, especially at lower rpms.  (..and they 
> are noisy.)
>   
Yes, you can use a closed-loop speed control, or convert the motor from 
series to
shunt with a controller.

Jon

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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[charles green]

so the motor in, say, a small drill press or a _bench grinder_ is probably of 
the resistive start winding type?

it would be nice to turn the rpms on a bench grinder way down for final 
figuring of certain cutter edges, to reduce removal rate, reduce heat at the 
cutter edge, and reduce innaccuracy from vibrations.

brushed ac motors are easy to turn up and down, but have a large defect of set 
point compliance with any loading, especially at lower rpms.  (..and they are 
noisy.)

any ideas?  reversible would be nice too, to improve the lathe toolpost grinder 
for example.  (dremel type tools work ok for small small small stuff, but tend 
to have really sloppy bearings.  (..and they are noisy.))



--- On Tue, 3/6/12, Jon Elson  wrote:

> From: Jon Elson 
> Subject: Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11
> To: "Enhanced Machine Controller (EMC)" 
> Date: Tuesday, March 6, 2012, 10:13 AM
> charles green wrote:
> > what are the differences between one phase motors, two
> phase motors, and three phase motors?
> >
> >
> >   
> A single-phase motor needs something to get it started, as
> there is no phase
> rotation to cause the rotor to start turning.  There
> are shaded-pole motors,
> resistive-start, capacitor start,
> capacitor-start/capacitor-run motors and
> capacitor-run variations.
> These generally have centrifugal starting switches that shut
> off the 
> start winding
> when the motor is up to speed.  The shaded pole and
> cap-run motors do
> not have the starting switch, though.  The resistive
> start winding or
> the capacitor creates a phase angle shift that provides the
> rotation for 
> starting.
> So, all of these except the shaded-pole are actually
> two-phase motors, but
> they generate the 2nd phase internally.
> 
> One problem with these motors is they are much less amenable
> to variable
> speed operation.  When equipped with a starting switch,
> then you can't
> run it below the speed where the switch turns on the start
> winding, as
> it will overheat the start winding.  When equipped with
> a capacitor,
> the proper phase angle shift is only obtained at one
> frequency.
> 
> You won't find true two-phase motors run from the power line
> except
> in the most unusual cases.  However, a stepper motor is
> usually a two-phase
> motor.
> 
> Three phase motors have 3 sets of windings arranged around
> the stator,
> and the phase sequence provides the rotation for
> starting.  So, no
> capacitors or switches are needed for starting, making the
> motors
> much simpler and more reliable.  Since there are no
> special arrangements
> for starting, these motors are much easier to operate off a
> variable 
> frequency
> supply to get variable speed.  The voltage applied
> should be proportional
> to the frequency.
> 
> Jon
> 
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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Jon Elson]

charles green wrote:
> what are the differences between one phase motors, two phase motors, and 
> three phase motors?
>
>
>   
Oh, I wanted to add that a 2-phase motor has a 90 degree phase shift between
the two pases.  A 3-phase motor has a 120 degree shift between phases.

Jon

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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Jon Elson]

charles green wrote:
> what are the differences between one phase motors, two phase motors, and 
> three phase motors?
>
>
>   
A single-phase motor needs something to get it started, as there is no phase
rotation to cause the rotor to start turning.  There are shaded-pole motors,
resistive-start, capacitor start, capacitor-start/capacitor-run motors and
capacitor-run variations.
These generally have centrifugal starting switches that shut off the 
start winding
when the motor is up to speed.  The shaded pole and cap-run motors do
not have the starting switch, though.  The resistive start winding or
the capacitor creates a phase angle shift that provides the rotation for 
starting.
So, all of these except the shaded-pole are actually two-phase motors, but
they generate the 2nd phase internally.

One problem with these motors is they are much less amenable to variable
speed operation.  When equipped with a starting switch, then you can't
run it below the speed where the switch turns on the start winding, as
it will overheat the start winding.  When equipped with a capacitor,
the proper phase angle shift is only obtained at one frequency.

You won't find true two-phase motors run from the power line except
in the most unusual cases.  However, a stepper motor is usually a two-phase
motor.

Three phase motors have 3 sets of windings arranged around the stator,
and the phase sequence provides the rotation for starting.  So, no
capacitors or switches are needed for starting, making the motors
much simpler and more reliable.  Since there are no special arrangements
for starting, these motors are much easier to operate off a variable 
frequency
supply to get variable speed.  The voltage applied should be proportional
to the frequency.

Jon

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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Kirk Wallace]

On Tue, 2012-03-06 at 04:22 -0800, charles green wrote:
> what are the differences between one phase motors, two phase motors, and 
> three phase motors?

Generally, single phase power can be described with a single sine wave.
The sine wave is the voltage measured between L1 and L2 on the mains and
in the US is 220 to 240 Vac. 110 or 120 Vac is also single phase but the
sine wave is derived by L1 and N (Neutral) or L2 and N. The most basic
single phase motor might have a rotor with a North and South pole and a
stator with a single N and S. One way to visualize this is in
considering a drive wheel, push rod and piston of a steam engine. The
piston can only push and pull in one direction and the wheel can spin in
either direction. Single phase motors need some sort of starting feature
to get the motor rotating in the proper direction. Also, they use two
power wires and a safety ground wire.

Two phase power generally has two phases that are shifted time wise by
90 (and 270) degrees or a quarter wave length. There are two separate
phases, so four wires are needed on the motor. A piston engine
configured in a 90 degree V would be similar. Motors and engines will
start and run only in one direction. Some early power stations provided
two phase power but this didn't last long. Two phase is now most
commonly used on stepper motors.

Three phase power has three sine waves shifted by 120 degrees. With this
timing, three phase power needs only three wires, L1, L2, L3, instead of
six wires if the phase timing were shifted by 90 degrees as in two phase
described above. This, most likely, is why two phase mains power didn't
last very long. A radial engine with three pistons spaced 120 degrees
apart would have the same push-pull forces on the crank shaft as on the
three phase motor rotor. As with two phase motors, the motor will start
and run in only one direction.

As always, Wikipedia has a lot of information on this:
http://en.wikipedia.org/wiki/Single-phase_electric_power 
http://en.wikipedia.org/wiki/Two-phase_electric_power 
http://en.wikipedia.org/wiki/Three-phase_electric_power 
-- 
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA


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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Joachim Franek]

On Tuesday 06 March 2012 13:22:26 charles green wrote:
> what are the differences between one phase motors, two phase motors, and 
> three phase motors?

http://en.wikipedia.org/wiki/Electric_motor

One phase: 
can not start, because there is no torque at 0 speed.
Has to be moved by hand in one direction and
accelerates then to the nominal speed. Can
be started in each rotating direction.

Two Phase: 
usually used with a capacitor to phase
shift the current in one of the phases.
Runs on one phase systems and starts
in the right direction with low torque
near speed 0.

Three phase:
See wikipedia. 
Asynchronous type: has no permanent magnets,
rotates slower compared to the driving frequency (=slip).
slip=function of torque.

Synchronous type (PMSM):
Rotates with the same frequency, but
angle between induced magnetic field
and permanent magnet is a function of torque.

Joachim 

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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[charles green]

what are the differences between one phase motors, two phase motors, and three 
phase motors?


--- On Sun, 3/4/12, Jon Elson  wrote:

> From: Jon Elson 
> Subject: Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11
> To: "Enhanced Machine Controller (EMC)" 
> Date: Sunday, March 4, 2012, 11:29 AM
> Joachim Franek wrote:
> > But I see cross current
> > in case one leg is  active from pwm and a 
> > commutation occurs. Then for about 120ns
> > I measure a current of 70A (peak).  
> > I need a comp to delay the rising edge
> > on the upper fet for one cycle of the fast thread
> > in case in the last cycle the fet was on.
> >   
> Do not try to control FET dead-time with software. 
> Very simple
> RC circuits with an added diode to reduce the R in one
> direction
> have been used for years.  The R delays turn-on, the
> diode
> causes fast turn-off.
> 
> Jon
> 
> --
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Re: [Emc-users] IRAMS Plan

[Joachim Franek]

FNB41060 - IGBT SMART PM,600V,10A
< 10 Euro at Farnell


Joachim 

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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Joachim Franek]

On Sunday 04 March 2012 18:12:09 Kirk Wallace wrote:
> I don't know what a SPSM motor is, but from this they can get big:
> http://www-personal.engin.umd.umich.edu/~chrismi/publications/2009_45_12_TMAG_Solid_equi.pdf
>  


Excuse the typo:
PMSM: permanent magnet synchronous motor 

All test are with 24V.

Joachim 


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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Jon Elson]

Joachim Franek wrote:
> But I see cross current
> in case one leg is  active from pwm and a 
> commutation occurs. Then for about 120ns
> I measure a current of 70A (peak).  
> I need a comp to delay the rising edge
> on the upper fet for one cycle of the fast thread
> in case in the last cycle the fet was on.
>   
Do not try to control FET dead-time with software.  Very simple
RC circuits with an added diode to reduce the R in one direction
have been used for years.  The R delays turn-on, the diode
causes fast turn-off.

Jon

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Re: [Emc-users] IRAMS Plan

[Kirk Wallace]

On Sun, 2012-03-04 at 13:19 +0200, Roland Jollivet wrote:
> On 3 March 2012 19:03, Kirk Wallace  wrote:
> 
> >
> > I was thinking of using an AVR analog input to sense the IRAMS internal
> > sense resistor then use software to look for current peaks and separate
> > the leg currents if needed, but this is much easier to plan, than to
> > make real.
> >
> >
> >
> Maybe this was discussed already...
> 
> If you're using an AVR, and this is a spindle motor, then why not use an
> encoder on the motor, or at least the index pulse, to create your own phase
> signals. You could even shift the phase(3) to optimize the power, much like
> the offset brushes on DC motors (for reverse too). So it's all 'soft'
> commutation.
> 
> Regards
> Roland
... snip

In my study, I want to have as many functions as possible stay in
LinuxCNC and use the AVR for analog conversion or processing that may be
better done locally at the driver, such as fault detection or backup. If
the commutation signals where analog, I would tend to digitize them in
the AVR, then pass the data to LinuxCNC for processing.
-- 
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA


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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Kirk Wallace]

On Sun, 2012-03-04 at 11:43 +0100, Joachim Franek wrote:
> Hello,
> 
> I can report some progress for my attempts to
> drive 3 phase motors. I do this to be familiar with the 
> bldc component and use for safety low voltage devices.
> 
> My setups:
> Electronics: FAN7382 and BUZ11 board
> (http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Bridges_-_Half,_Full,_Three_Phase)
> Hal:
> loadrt threads name1=fast fp1=0 period1=5 name2=slow period2=100
> loadrt encoder num_chan=1 (parport is used)
> 
> 1. BLDC motor 24V 100W; 3 hall signals; encoder 3ch, 500 
> loadrt bldc cfg=hB6
> loadrt pwmgen output_type=0 (to the upper fets)
> setp bldc.0.pattern   0x0019
> 
> 2. SPSM motor (Panasonic)  62V 200W; no hall signals; encoder 3ch, 2500

I don't know what a SPSM motor is, but from this they can get big:
http://www-personal.engin.umd.umich.edu/~chrismi/publications/2009_45_12_TMAG_Solid_equi.pdf
 

> loadrt bldc cfg=iqB6
> loadrt pwmgen output_type=0 (to the upper fets)
> setp bldc.0.poles 8
> setp bldc.0.scale 1
> 
> 3. Asynchon motor 230V triangle, 120W; encoder 3ch, 500
> loadrt bldc cfg=n
> loadrt pwmgen output_type=2,2,2 (to all fets)
> 
> Results:
> 1 and 2 works nice. 
> Speed is limited from encoder parport usage.

Sounds like you are ready for an FPGA card (if you had one).

> But I see cross current
> in case one leg is  active from pwm and a 
> commutation occurs. Then for about 120ns
> I measure a current of 70A (peak).  
> I need a comp to delay the rising edge
> on the upper fet for one cycle of the fast thread
> in case in the last cycle the fet was on.
> And the same for changed roles.
> I think in case of a high voltage setup this
> destroys something.

That has been my understanding from my reading on the subject. The
higher voltage arena really takes the bar to a higher level. The IRAM
series of modules advertise features that safeguard against
shoot-through due to lax signal timing.

> To 3: Up to 5Hz this works. Distorted
> (pwm sine modulated) currents are observed
> because of limited pwm resolution.

What area are you located? I could send you a Pluto-P and EPP parallel
port PCI card, which could provide much faster I/O. I'm concerned the
postage would be prohibitive.

-- 
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA


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[Emc-users] IRAMS Plan

[Roland Jollivet]

On 3 March 2012 19:03, Kirk Wallace  wrote:

>
> I was thinking of using an AVR analog input to sense the IRAMS internal
> sense resistor then use software to look for current peaks and separate
> the leg currents if needed, but this is much easier to plan, than to
> make real.
>
>
>
Maybe this was discussed already...

If you're using an AVR, and this is a spindle motor, then why not use an
encoder on the motor, or at least the index pulse, to create your own phase
signals. You could even shift the phase(3) to optimize the power, much like
the offset brushes on DC motors (for reverse too). So it's all 'soft'
commutation.

Regards
Roland
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Re: [Emc-users] IRAMS Plan, FAN7382 with BUZ11

[Joachim Franek]

Hello,

I can report some progress for my attempts to
drive 3 phase motors. I do this to be familiar with the 
bldc component and use for safety low voltage devices.

My setups:
Electronics: FAN7382 and BUZ11 board
(http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Bridges_-_Half,_Full,_Three_Phase)
Hal:
loadrt threads name1=fast fp1=0 period1=5 name2=slow period2=100
loadrt encoder num_chan=1 (parport is used)

1. BLDC motor 24V 100W; 3 hall signals; encoder 3ch, 500 
loadrt bldc cfg=hB6
loadrt pwmgen output_type=0 (to the upper fets)
setp bldc.0.pattern   0x0019

2. SPSM motor (Panasonic)  62V 200W; no hall signals; encoder 3ch, 2500
loadrt bldc cfg=iqB6
loadrt pwmgen output_type=0 (to the upper fets)
setp bldc.0.poles 8
setp bldc.0.scale 1

3. Asynchon motor 230V triangle, 120W; encoder 3ch, 500
loadrt bldc cfg=n
loadrt pwmgen output_type=2,2,2 (to all fets)

Results:
1 and 2 works nice. 
Speed is limited from encoder parport usage.

But I see cross current
in case one leg is  active from pwm and a 
commutation occurs. Then for about 120ns
I measure a current of 70A (peak).  
I need a comp to delay the rising edge
on the upper fet for one cycle of the fast thread
in case in the last cycle the fet was on.
And the same for changed roles.
I think in case of a high voltage setup this
destroys something.

To 3: Up to 5Hz this works. Distorted
(pwm sine modulated) currents are observed
because of limited pwm resolution.


Joachim 

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Re: [Emc-users] IRAMS Plan

[Joachim Franek]

> Any suggestions are welcome.

Hello.

Overvoltage protection:
If the motor acts as a generator DC voltage increases. 

1. Add a transistor which switches a resistor in parallel to the DC supply.
2. Add 6 and gates to stop motor commutation in case of to high DC voltage.


Joachim 

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Re: [Emc-users] IRAMS Plan

[gene heskett]

On Saturday, March 03, 2012 01:46:58 PM Peter C. Wallace did opine:

> On Sat, 3 Mar 2012, gene heskett wrote:
> > Date: Sat, 3 Mar 2012 12:20:02 -0500
> > From: gene heskett 
> > Reply-To: "Enhanced Machine Controller (EMC)"
> > 
> > 
> > 
> > To: emc-users@lists.sourceforge.net
> > Subject: Re: [Emc-users] IRAMS Plan
> > 
> > On Saturday, March 03, 2012 12:03:01 PM Przemek Klosowski did opine:
> >>>> Anders, can You suggest, how to implement that (preferably a simple
> >>>> and easy way, so that even child or golden retriever :) would
> >>>> understand)? The scheme in my IRAMS datasheet suggests using Shunt
> >>>> resistors for that, but I suspect that something else should also
> >>>> be needed, but I have no idea, how these things actually work.
> >> 
> >> In principle you could measure the current by attaching current
> >> transformers or Hall sensors to the motor leads, avoiding the
> >> high-side and high common mode voltage issues. The downside might be
> >> speed/frequency response. What do people think about these
> >> alternatives to resistive shunts?
> > 
> > Excellent idea.  Current transformers can have frequency response
> > problems depending on the magnetic materials used. but are pretty
> > accurate.  Hall effect stuff is probably faster but from my
> > experience, not as linear.
> > 
> > For this duty, either should be more than fast enough.  One of the
> > side effects of the current transformer will be a slowing of the
> > Di-Dt under fault conditions, which may give enough time for
> > shutdowns to be done.  To me its advantageous when a $1 fuse blows
> > instead of the $500 circuit. :)
> > 
> > The current transformers output voltage will be very high under fault
> > conditions, so figure on some sort of over-voltage protection in the
> > circuitry its feeding so it doesn't get blown by a momentary carbon
> > track as a June bug gets to meet its maker.
> > 
> > Oh, and Kirchoffs applies to the delta connected circuit.  Barring
> > ground faults, sensing any 2 is sufficient.  But around machinery,
> > and in the real world, ground faults DO happen and I would design
> > accordingly. IOW, sense all three phases.
> > 
> > Cheers, Gene
> 
> Note that current transformers will not work on PMSM (permanet magnet
> rotor motors) as these can have DC drive current when applying constant
> torque when stalled.

I had forgotten that (can I blame it on oldtimers?) detail Peter, many 
thanks for bailing me out.

I was thinking only in terms of the AC input power, which can put a pretty 
decent energy sink in the path, and slowing the response since a fault 
would have to dump the sink before it would show up in the input currents.  

That sink dumping can easily turn semiconductor stuff into lid-less smoke 
generators. :(

However, and back to "load" sensing, I was under the impression that 
stalled torque in these was probably limited by the duty cycle of a pwm 
drive, and that should still give a signal.  What that signal means could 
be subject to interpretation of course since the AC isn't going to 
represent even a fraction of the DC flowing when the DC is largely the 
free-wheeling current flow when the pwm is in the off state.

In that case, would it not make more sense to pass the low side currents 
thru a fullwave bridge with a very small R as its load so that an led would 
light up and initiate the shutdown when it comes on?  I have an ammeter I 
made that works on that idea so I can see how hard my spindle motor is 
working since its control is so stiff, the rpm change from no load to 
blowing a fuse is perhaps 1%.

> Normally you need to measure 2 phase currents. Common way to do this is
> with Hall effect devices in the motor leads (this works because the
> Hall effect devices are isolated so the 360V PWM voltage does not
> affect them)
> 
> The other way to measure phase currents is with 3 current shunt
> resistors in the three bottom IRAM 1/2 bridge legs (on the modeules
> that bring the individual emitter pins out). Its more difficult to get
> good current reading here as the current is only valid when the bottom
> leg of the shunt resistors 1/2 bridge is on (and the shunt voltage must
> be measured when switching transients have died down). This leads to
> interesting code to select the best 2 shunt resistors to sample
> depending on the drive phase angle and polarity.
> 
> IF you are not using shunt resistors for current control (FOC) you can
> use the IRAM modules with a built-in single shunt resistor (and
> assosciated comparator and shut down logic) in 

Re: [Emc-users] IRAMS Plan

[Greg Bernard]

You might take a look at this application note for some ideas: 
http://jrkerr.com/pssc_irams.zip. 




>
> From: Anders Wallin 
>To: Enhanced Machine Controller (EMC)  
>Sent: Saturday, March 3, 2012 8:38 AM
>Subject: Re: [Emc-users] IRAMS Plan
> 
>> Anders, can You suggest, how to implement that (preferably a simple
>> and easy way, so that even child or golden retriever :) would
>> understand)? The scheme in my IRAMS datasheet suggests using Shunt
>> resistors for that, but I suspect that something else should also be
>> needed, but I have no idea, how these things actually work.
>
>I don't know the details. You/we should encourage M.Martsola of
>granitedevices, or M.Freimanis of geckodrive, or linuxcnc's own
>P.Wallace of Mesa to give comments on the details of the design and/or
>share an open-hardware servodrive design.
>
>So without going into details:
>- shunt-resistor on the phase where you want to measure current. Make
>sure the resistor can handle the power.
>- in principle it is enough to measure 2 phases, and the third current
>can be deduced from the other two (Kirchoff!). At least for the
>popular Y-connection. Not sure about delta/Wye connection.
>- The voltage drop across the shunt is going to be small (we don't
>want a lot of power wasted in the shunt), so it needs amplification.
>- The differential amp that monitors the voltage drop needs to be able
>to handle high common-mode voltage, possibly up to the maximum DC
>voltage of the drive if the shunts are 'before' the motor windings
>(called high-side-sensing).
>- The amp also needs to handle noise and voltage spikes well. The
>inductance of the motor windings will filter the PWM to some extent,
>but a lot of the PWM-frequency and its higher harmonics will remain.
>Maybe add low-pass filtering on the amp-output also.
>- For fault-protection the amp-output should be compared to a pre-set
>current-limit, and the result used to shutdown the IRAMS. Possibly
>this fault-condition should also connect a braking resistor across the
>motor windings.
>- For continuous current-sensing the signal should be digitized. To
>save input pins on the fpga a serial format (pwm, pulse-frequency,
>I2C?) would probably be best.
>
>Back in 2006 I tried using IRF's own IR2175 for this
>http://www.anderswallin.net/wp-content/2006_06servo/proto_powerstage.pdf
>but somehow this wasn't working very well, and if my control-logic
>would command full power from the IRAMS then frying the drive without
>tripping the current-limit was possible.
>I'd encourage any new design to use fast hard-wired
>current-sensing/limiting solution to make the power-stage as
>fool-proof as possible (user & programming errors will happen!)
>
>Anders
>
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Re: [Emc-users] IRAMS Plan

[Peter C. Wallace]

On Sat, 3 Mar 2012, gene heskett wrote:

> Date: Sat, 3 Mar 2012 12:20:02 -0500
> From: gene heskett 
> Reply-To: "Enhanced Machine Controller (EMC)"
> 
> To: emc-users@lists.sourceforge.net
> Subject: Re: [Emc-users] IRAMS Plan
> 
> On Saturday, March 03, 2012 12:03:01 PM Przemek Klosowski did opine:
>
>>>> Anders, can You suggest, how to implement that (preferably a simple
>>>> and easy way, so that even child or golden retriever :) would
>>>> understand)? The scheme in my IRAMS datasheet suggests using Shunt
>>>> resistors for that, but I suspect that something else should also be
>>>> needed, but I have no idea, how these things actually work.
>>
>> In principle you could measure the current by attaching current
>> transformers or Hall sensors to the motor leads, avoiding the
>> high-side and high common mode voltage issues. The downside might be
>> speed/frequency response. What do people think about these
>> alternatives to resistive shunts?
>
> Excellent idea.  Current transformers can have frequency response problems
> depending on the magnetic materials used. but are pretty accurate.  Hall
> effect stuff is probably faster but from my experience, not as linear.
>
> For this duty, either should be more than fast enough.  One of the side
> effects of the current transformer will be a slowing of the Di-Dt under
> fault conditions, which may give enough time for shutdowns to be done.  To
> me its advantageous when a $1 fuse blows instead of the $500 circuit. :)
>
> The current transformers output voltage will be very high under fault
> conditions, so figure on some sort of over-voltage protection in the
> circuitry its feeding so it doesn't get blown by a momentary carbon track
> as a June bug gets to meet its maker.
>
> Oh, and Kirchoffs applies to the delta connected circuit.  Barring ground
> faults, sensing any 2 is sufficient.  But around machinery, and in the real
> world, ground faults DO happen and I would design accordingly. IOW, sense
> all three phases.
>
> Cheers, Gene
> -- 
> "There are four boxes to be used in defense of liberty:
> soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> My web page: <http://coyoteden.dyndns-free.com:85/gene>
> Lead me not into temptation... I can find it myself.

Note that current transformers will not work on PMSM (permanet magnet rotor 
motors) as these can have DC drive current when applying constant torque when 
stalled.

Normally you need to measure 2 phase currents. Common way to do this is with 
Hall effect devices in the motor leads (this works because the Hall effect 
devices are isolated so the 360V PWM voltage does not affect them)

The other way to measure phase currents is with 3 current shunt resistors in 
the three bottom IRAM 1/2 bridge legs (on the modeules that bring the 
individual emitter pins out). Its more difficult to get good current reading 
here as the current is only valid when the bottom leg of the shunt resistors 
1/2 bridge is on (and the shunt voltage must be measured when switching 
transients have died down). This leads to interesting code to select the best 
2 shunt resistors to sample depending on the drive phase angle and polarity.

IF you are not using shunt resistors for current control (FOC) you can 
use the IRAM modules with a built-in single shunt resistor (and assosciated 
comparator and shut down logic) in the bottom leg of the IRAM module for
over current protection.

For a simple voltage mode device this may be enough protection.

As gene mentioned, this will not protect against U,V,W to ground shorts
that normal requires fast sensing in U,V,W motor wires or both high and low 
side VBUS current sensing


Note that the modules are NOT isolated, all the gate drive and fault signals 
are relative to the negative VBUS terminal so you need to provide isolation. 
(I think 3750V isolation from SELV signals is a legal requiremant for 240V 
line operated equipment)

Rather than try and isolate all the analog (VBUS,phase currents), gate drive, 
fault, and temperaure sense stuff (something like 12 signals in our case) , on 
our 3 phase drives the processor ground runs at VBUS- and the isolation is 
just in the 2 serial comm lines.


Peter Wallace
Mesa Electronics


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Re: [Emc-users] IRAMS Plan

[Eric Keller]

On Sat, Mar 3, 2012 at 4:12 AM, Viesturs Lācis wrote:

> 2012/3/3 Anders Wallin :
> >
> > To make your design fool-proof you need to sense current, possibly on
> > all three motor phases, and do it reliably and quickly in order to
> > shutdown the IRAMS and/or pwm-source when something bad happens.
>
> Anders, can You suggest, how to implement that (preferably a simple
> and easy way, so that even child or golden retriever :) would
> understand)? The scheme in my IRAMS datasheet suggests using Shunt
> resistors for that, but I suspect that something else should also be
> needed, but I have no idea, how these things actually work.
>
> Viesturs
>
> I used hall effect sensors because they were already built and available.
They do have some problems with linearity and offset and are pretty
expensive.  I was thinking about going with the Allegro current sensing
chips for my next design.
Eric
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Re: [Emc-users] IRAMS Plan

[gene heskett]

On Saturday, March 03, 2012 12:03:01 PM Przemek Klosowski did opine:

> >> Anders, can You suggest, how to implement that (preferably a simple
> >> and easy way, so that even child or golden retriever :) would
> >> understand)? The scheme in my IRAMS datasheet suggests using Shunt
> >> resistors for that, but I suspect that something else should also be
> >> needed, but I have no idea, how these things actually work.
> 
> In principle you could measure the current by attaching current
> transformers or Hall sensors to the motor leads, avoiding the
> high-side and high common mode voltage issues. The downside might be
> speed/frequency response. What do people think about these
> alternatives to resistive shunts?
 
Excellent idea.  Current transformers can have frequency response problems 
depending on the magnetic materials used. but are pretty accurate.  Hall 
effect stuff is probably faster but from my experience, not as linear.

For this duty, either should be more than fast enough.  One of the side 
effects of the current transformer will be a slowing of the Di-Dt under 
fault conditions, which may give enough time for shutdowns to be done.  To 
me its advantageous when a $1 fuse blows instead of the $500 circuit. :)

The current transformers output voltage will be very high under fault 
conditions, so figure on some sort of over-voltage protection in the 
circuitry its feeding so it doesn't get blown by a momentary carbon track 
as a June bug gets to meet its maker.

Oh, and Kirchoffs applies to the delta connected circuit.  Barring ground 
faults, sensing any 2 is sufficient.  But around machinery, and in the real 
world, ground faults DO happen and I would design accordingly. IOW, sense 
all three phases.

Cheers, Gene
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
My web page: 
Lead me not into temptation... I can find it myself.

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Re: [Emc-users] IRAMS Plan

[Kirk Wallace]

On Sat, 2012-03-03 at 09:40 +0200, Anders Wallin wrote:
... snip
> IIRC what can cause a sudden death of the IRAMS is overcurrent for
> some reason or another.
> To make your design fool-proof you need to sense current, possibly on
> all three motor phases, and do it reliably and quickly in order to
> shutdown the IRAMS and/or pwm-source when something bad happens.
> 
> For permanent magnet servos the current-sensing is just
> fault-protection. If the current-sensing can be made to work
> accurately the same power-stage could maybe be used for induction
> motors with a vector-drive algorithm. Possibly this requires
> voltage-sensing on the uvw-phases also?

This document shows what I think is a kind of sample hold arrangement in
the lower right corner.
http://www.jrkerr.com/pssc_irams.zip 

I was thinking of using an AVR analog input to sense the IRAMS internal
sense resistor then use software to look for current peaks and separate
the leg currents if needed, but this is much easier to plan, than to
make real.

> With higher voltage/current the IRAMS will require cooling. I used an
> old cpu-heatsink+fan. You might want to put the psu/power-wiring for
> this on the IRAMS-PCB also.

I'm not seeing your point here. I have a couple of 1/2 HP VFD's here I
can study and plan on copying their layout with a diode bridge and set
of caps feeding the DC bus. I'll feed it from a transformer for the
lower voltage study, then try mains input latter.

I was a little surprised to see the outside of the module is all plastic
which isn't the best heat conductor, but I suppose good enough in this
case. I suppose one really needs to make sure this IRAMS operates at its
highest efficiency.

> Optoisolation between the power-stage and the fpga-logic would be a good idea.
... snip

The datasheet indicates that the chip is already isolated. Since
isolation can slow the signals I had not planed on additional isolation,
but I see from the datasheet that the sense resistor is internally tied
to Vss or logic ground. The thermistor is tied to Vss so it may need to
be isolated. Itrip is on the other side of the sense resistor, so it
needs to be considered too. This issue might not be easy. Maybe I can
process these signals on the AVR and isolate the communications between
the AVR and the PC.

-- 
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http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA


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Re: [Emc-users] IRAMS Plan

[Przemek Klosowski]

>> Anders, can You suggest, how to implement that (preferably a simple
>> and easy way, so that even child or golden retriever :) would
>> understand)? The scheme in my IRAMS datasheet suggests using Shunt
>> resistors for that, but I suspect that something else should also be
>> needed, but I have no idea, how these things actually work.

In principle you could measure the current by attaching current
transformers or Hall sensors to the motor leads, avoiding the
high-side and high common mode voltage issues. The downside might be
speed/frequency response. What do people think about these
alternatives to resistive shunts?

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Re: [Emc-users] IRAMS Plan

[Anders Wallin]

> Anders, can You suggest, how to implement that (preferably a simple
> and easy way, so that even child or golden retriever :) would
> understand)? The scheme in my IRAMS datasheet suggests using Shunt
> resistors for that, but I suspect that something else should also be
> needed, but I have no idea, how these things actually work.

I don't know the details. You/we should encourage M.Martsola of
granitedevices, or M.Freimanis of geckodrive, or linuxcnc's own
P.Wallace of Mesa to give comments on the details of the design and/or
share an open-hardware servodrive design.

So without going into details:
- shunt-resistor on the phase where you want to measure current. Make
sure the resistor can handle the power.
- in principle it is enough to measure 2 phases, and the third current
can be deduced from the other two (Kirchoff!). At least for the
popular Y-connection. Not sure about delta/Wye connection.
- The voltage drop across the shunt is going to be small (we don't
want a lot of power wasted in the shunt), so it needs amplification.
- The differential amp that monitors the voltage drop needs to be able
to handle high common-mode voltage, possibly up to the maximum DC
voltage of the drive if the shunts are 'before' the motor windings
(called high-side-sensing).
- The amp also needs to handle noise and voltage spikes well. The
inductance of the motor windings will filter the PWM to some extent,
but a lot of the PWM-frequency and its higher harmonics will remain.
Maybe add low-pass filtering on the amp-output also.
- For fault-protection the amp-output should be compared to a pre-set
current-limit, and the result used to shutdown the IRAMS. Possibly
this fault-condition should also connect a braking resistor across the
motor windings.
- For continuous current-sensing the signal should be digitized. To
save input pins on the fpga a serial format (pwm, pulse-frequency,
I2C?) would probably be best.

Back in 2006 I tried using IRF's own IR2175 for this
http://www.anderswallin.net/wp-content/2006_06servo/proto_powerstage.pdf
but somehow this wasn't working very well, and if my control-logic
would command full power from the IRAMS then frying the drive without
tripping the current-limit was possible.
I'd encourage any new design to use fast hard-wired
current-sensing/limiting solution to make the power-stage as
fool-proof as possible (user & programming errors will happen!)

Anders

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Re: [Emc-users] IRAMS Plan

[Viesturs Lācis]

2012/3/3 Anders Wallin :
>
> To make your design fool-proof you need to sense current, possibly on
> all three motor phases, and do it reliably and quickly in order to
> shutdown the IRAMS and/or pwm-source when something bad happens.

Anders, can You suggest, how to implement that (preferably a simple
and easy way, so that even child or golden retriever :) would
understand)? The scheme in my IRAMS datasheet suggests using Shunt
resistors for that, but I suspect that something else should also be
needed, but I have no idea, how these things actually work.

Viesturs

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Re: [Emc-users] IRAMS Plan

[Anders Wallin]

> Attached is my first pass at an IRAMS circuit. It's pretty much a copy
> of the IRF datasheet example. The plan is to hook up the digital signals
> to an FPGA card, Pluto-P if I can find it, or 5i25 if I sell something
> on eBay. The analog signals are an unknown for now. IRF seems to
> recommend using a ceramic capacitor with each electrolytic, I need to
> learn more about this as well as chose a size for the motor input caps.
> Any suggestions are welcome.

IIRC what can cause a sudden death of the IRAMS is overcurrent for
some reason or another.
To make your design fool-proof you need to sense current, possibly on
all three motor phases, and do it reliably and quickly in order to
shutdown the IRAMS and/or pwm-source when something bad happens.

For permanent magnet servos the current-sensing is just
fault-protection. If the current-sensing can be made to work
accurately the same power-stage could maybe be used for induction
motors with a vector-drive algorithm. Possibly this requires
voltage-sensing on the uvw-phases also?

With higher voltage/current the IRAMS will require cooling. I used an
old cpu-heatsink+fan. You might want to put the psu/power-wiring for
this on the IRAMS-PCB also.

Optoisolation between the power-stage and the fpga-logic would be a good idea.

AW

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Re: [Emc-users] IRAMS Plan

[Kirk Wallace]

On Fri, 2012-03-02 at 13:17 -0800, Karl Cunningham wrote:
... snip
> What DC bus voltage are you planning to feed to the IRAMS module?

I have a 45 Volt motor to start testing with. I 'll probably start at 30
to 50 Volts depending on what supply I can scrounge up, then go up from
there. I would like to go up to 240 Volts.

>  I 
> would think a low-ESR capacitor of 1 or 2 microfarad would be desirable 
> across the DC bus, located right next to the IRAMS module. A low-ESR 
> film capacitor should work about as well as a ceramic and may be 
> easier/cheaper to find if the voltage is very high.

That's what the datasheet seems to recommend except they recommend both
the ceramic and electrolytic caps together.

> Motor input caps? Are these the 2.2uF caps in your schematic?

No, I meant the motor power supply caps.

>  I think 
> these are bootstrap capacitors, used to generate a voltage inside the 
> chip to drive the gates of the top switches.
> Have a look here: http://www.irf.com/technical-info/designtp/dt04-4.pdf
> 
> Their minimum capacitance depends on how much voltage you have on your 
> DC bus, what your switching frequency is going to be, and what minimum 
> duty cycle you plan to have. Are any of these things known?

Not really, but the datasheet recommends 2.2 uF above something like 12
kHz, so the plan is for 2.2 uF. It seems these can be fairly low
voltage. I'll probably go for 50 Volt electrolytic caps.

> Grounding is key to using these modules. Especially at high voltage. For 
> breadboarding, try to do it on a board with a copper plane. Without 
> this, it's not hard to get switching spikes across ground lines which 
> are large enough to turn a logic 1 into a logic 0. When that happens, 
> things can go bang very quickly.
> 
> Karl

I don't have my PC board machining setup done, or even started. I guess
ordering parts might have been a little premature. I'll either need to
order prototype boards from BatchPCB or finish my engraving spindle
first.

I got the IRAMS module in today, it's cute, I'm having a hard time
believing I can run a 1/2 to 1 HP motor with it. After poking around
Digikey some more, I noticed there is a 4 HP module available, I want
it.
-- 
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http://www.wallacecompany.com/E45/index.html
California, USA


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Re: [Emc-users] IRAMS Plan

[Karl Cunningham]

On 03/02/2012 11:38 AM, Kirk Wallace wrote:
> (First Message may have failed due to attachment too big)
>
> Attached is my first pass at an IRAMS circuit. It's pretty much a copy
> of the IRF datasheet example. The plan is to hook up the digital signals
> to an FPGA card, Pluto-P if I can find it, or 5i25 if I sell something
> on eBay. The analog signals are an unknown for now. IRF seems to
> recommend using a ceramic capacitor with each electrolytic, I need to
> learn more about this as well as chose a size for the motor input caps.
> Any suggestions are welcome.

Kirk,

What DC bus voltage are you planning to feed to the IRAMS module? I 
would think a low-ESR capacitor of 1 or 2 microfarad would be desirable 
across the DC bus, located right next to the IRAMS module. A low-ESR 
film capacitor should work about as well as a ceramic and may be 
easier/cheaper to find if the voltage is very high.

Motor input caps? Are these the 2.2uF caps in your schematic? I think 
these are bootstrap capacitors, used to generate a voltage inside the 
chip to drive the gates of the top switches.
Have a look here: http://www.irf.com/technical-info/designtp/dt04-4.pdf

Their minimum capacitance depends on how much voltage you have on your 
DC bus, what your switching frequency is going to be, and what minimum 
duty cycle you plan to have. Are any of these things known?

Grounding is key to using these modules. Especially at high voltage. For 
breadboarding, try to do it on a board with a copper plane. Without 
this, it's not hard to get switching spikes across ground lines which 
are large enough to turn a logic 1 into a logic 0. When that happens, 
things can go bang very quickly.

Karl

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Re: [Emc-users] IRAMS Plan

[Kirk Wallace]

On Fri, 2012-03-02 at 21:52 +0200, Viesturs Lācis wrote:
... snip
> >From my discussions with Andy Pugh our agreement was that 3-phase
> pwmgen output from Mesa card should be the thing to feed into IRAMS
> module.
... snip

The parallel port is too slow. I already have a Pluto-P and Pico UPC. I
think the 5i25 would be better suited for this application, but not
required. I think the three high side inputs will be switched, then the
three low side inputs PWM'ed for current control or for sine wave form
if needed. The analog I/O may be done with a small AVR to convert analog
to 2 or 3 x 4 bit digital. The analog plan is to do just enough to
handle these analog signals and keep real-time.
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Re: [Emc-users] IRAMS Plan

[Viesturs Lācis]

2012/3/2 Kirk Wallace :
> (First Message may have failed due to attachment too big)
>
> Attached is my first pass at an IRAMS circuit. It's pretty much a copy
> of the IRF datasheet example. The plan is to hook up the digital signals
> to an FPGA card, Pluto-P if I can find it, or 5i25 if I sell something
> on eBay.

>From Your scheme it seems like You are not yet sure, how to create
signal for PWM inputs.
>From my discussions with Andy Pugh our agreement was that 3-phase
pwmgen output from Mesa card should be the thing to feed into IRAMS
module.

Viesturs

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[Emc-users] IRAMS Plan

[Kirk Wallace]

(First Message may have failed due to attachment too big)

Attached is my first pass at an IRAMS circuit. It's pretty much a copy
of the IRF datasheet example. The plan is to hook up the digital signals
to an FPGA card, Pluto-P if I can find it, or 5i25 if I sell something
on eBay. The analog signals are an unknown for now. IRF seems to
recommend using a ceramic capacitor with each electrolytic, I need to
learn more about this as well as chose a size for the motor input caps.
Any suggestions are welcome.
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