[Emc-users] Suggested replacement for Servo Dynamics SDFCC1020-12 amp?

[Dave Matthews]

Asking here because I see a lot of people retrofitting old equipment.

My wife has a long arm quilting machine that was made by Proto quire a few
years ago.  They were an industrial equipment maker that is long gone.  The
basic operation of the machine is to watch x and y encoders and stitch the
fabric keeping a constant (ish) distance between the stitches.  I suspect
that they are just calculating a velocity off of the encoder movements.
This feeds the differential inputs of a Servo Dynamics SDFCC1020-12 servo
amp that drives a brushed dc motor from a 90 volt pdc power supply.

The servo amp was slowly dying with power on faults.  I revived that by
replacing the electrolytic caps but the thing is still not right and the
alignment procedure won;t get to the correct motor rpm without causing
drift as zero machine movement.  It slowly stitches.  If I tune that out I
won't go the right speed so the stitch spacing is wrong.  I am goi that
feeds into the H bridge on the output but am not holding out much faith.

Any suggestions for a brushed DC servo amp that will handle 90 volts and
works with differential input?  The specs on the current amp are 118vd
peak, 112vdc continuous, 20 amp peak, 10 amp continuous with a 16kHz pwm
frequency.  Not real critical on any of them other than being over 90 volts
continuus.  I doubt that they are anywhere near the 10 amp limit.

Any suggestions on what to put in as a direct replacement.  I am about at
the point of using an arduino to read the input on an a to d pin and pwm a
mosfet.  The arduino will go fast enough in fast pwm mode.

Dave

___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] R2E3 retrofit

[linuxcnc]

 

Jon,

I'm working with older AMC analog drives now.   25A20's

What is the full part number of your drives?   Is it an 30A20AC ?

I like the AMC drive, even though I am having tuning problems (I think it is
the particular drive and/or motor.)

AMC tech support is pretty good.  I've called them several times..  They are
US, PST.

 

Noel.

Walnut Creek, CA

 

 


___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] R2E3 retrofit

[Eric Keller]

On Mon, Jul 11, 2022 at 12:36 PM Jon Elson  wrote:

> Is anyone else using AMC 30A20 servo amps?

I have used one of the 30A20AC drives, and there was another used to
pump hydraulic fluid at work.  Both of those came with heat sinks from
the factory.  Neither got particularly hot. I think I would still add
a heat sink.
Eric Keller
Boalsburg Pennsylvania


___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] R2E3 retrofit

[gene heskett]

On 7/11/22 12:34, Jon Elson wrote:

Hello,

Is anyone else using AMC 30A20 servo amps?  I now have two of these, 
waiting for another one to show up on eBay for a decent price.  How 
hot do these run?  The first one I got had no heat sink, the 2nd one 
had a heat sink with gigantic fins 1" tall. But, there was no heat 
sink grease on that one, which is kind of crazy.  So, I'm wondering if 
I even need a heat sink?  I do have some heat sink extrusion that is 
just the right width, and the fins are not so tall, so I can pack the 
amps closer together.  The datasheet shows 143 W dissipation at 
continuous rated output current, but I wonder how that averages out in 
typical milling machine applications?


Any thoughts?

Thanks,

Jon

In the FWIW category Jon, 143 watts at full song says they almost have 
to be ancient analog designs.

With electrolytic caps that are probably well past their use by date.

Whereas your own pwm-servo I've got 3 of, doesn't run anywhere near that 
much heat in normal
operation spinning a spindle motor. Ultrasonic switch mode stuff doesn't 
make a lot of heat.
 I don't want to guess at the knee weight  on the b-port, but the xy 
can be handled with a pair of
the 3NM 3 phase stepper/servo's, by direct drive to the screw. Ought to 
be able to get 100 IPM for

rapids.

Are you going to motorize the quill too? It can move faster than the 
knee in most cases but with

limited travel.

Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 



___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] R2E3 retrofit

[Jon Elson]

Hello,

Is anyone else using AMC 30A20 servo amps?  I now have two 
of these, waiting for another one to show up on eBay for a 
decent price.  How hot do these run?  The first one I got 
had no heat sink, the 2nd one had a heat sink with gigantic 
fins 1" tall. But, there was no heat sink grease on that 
one, which is kind of crazy.  So, I'm wondering if I even 
need a heat sink?  I do have some heat sink extrusion that 
is just the right width, and the fins are not so tall, so I 
can pack the amps closer together.  The datasheet shows 143 
W dissipation at continuous rated output current, but I 
wonder how that averages out in typical milling machine 
applications?


Any thoughts?

Thanks,

Jon



___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users