Glad you found it informative.
These motors are frequently called "forklift motors", probably
because, well, they were used in forklifts... Your Siemens controller
is likely a "forklift controller", assuming that the conversion
company didn't design one from scratch and have Siemens construct it
(them). It might be possible to find more information on that unit by
haunting industrial material handling equipment sites and forums.
It is possible that your controller also does some armature voltage
control, some sep-ex motor controller do, so that's something to keep
in mind when I go on about the armature having full battery voltage
on it continuously during operation. My controller is a dedicated
design by EHV Systems specifically for the SCT Rabbit vehicle, so
obviously SCT didn't find off-the-shelf controllers to be suitable in some way.
It might be possible to power the motor from 12 volts directly. You
would need to identify the field wiring and disconnect it from the
controller (label things first). On my motor the fields are powered
by a cable running in the flange on the output shaft end of the
motor, on a length of SO-type rubber cord. The fields draw only about
10 amperes at 120 volts, so not much is needed in the way of heavy
wiring. The low field current is also a reason that the controller
can be much simplified, no heavy current switching devices.
The armature connection is two additional cables exiting the motor
adjacent to the field cable. The armature in my controller is limited
to 275 amperes at 120 volts. I don't know what the armature would
draw at 12 volts, might not be enough to draw much of a spark when
connected. Because the motor has poor locked-rotor torque, it will
pull more current until it attains some rotational speed. Idle
current at 120 volts is about 10 amperes. If it looks like it is
going to try and spin up, you might give it some manual assistance to
get past that stall problem at low voltage.
Do inspect the brushes, if you get the motor running with stuck-ish
brushes, you risk a burned commutator, particularly at higher
voltage. I would check the brushes and then move on to investigating
the controller, the motor is about the least likely reason that you
get no response so far.
If the van is limited to second gear, how is reverse accomplished?
Shutting down the motor to reverse it's rotation seems like a
nightmare for an on-road vehicle, would make parking a real hassle.
Stop motor, reverse fields, restart motor, repeat as necessary. Uhg.
If you get it running, you might want to consider changing the
transmission setup. I use all four gears and reverse. 4th isn't
useful until about 50 MPH, but a lot will depend on your final drive
ratio. Don't some (all) of the old VW vans have reduction gearing
after the differential?
A link to my SCT Rabbit on the EV Album: http://evalbum.com/91
In particular, a PDF of the field and armature control circuitry in
the SCT controller, This will give a sense of how the motor expects
to be supplied with voltage:
http://web.archive.org/web/20111109035218/http://www.mrsharkey.com/SCT/field.pdf
At startup, K1 & K2 are energized, field gets full voltage (PWM is
disabled in controller card) the armature gets battery voltage
through two paralleled 3 ohm resistors and begins to rotate. When the
controller determines that the armature is spinning by monitoring the
voltage, it pulls in K3, directly connecting the armature to the
batteries, and the PWM circuit (Darlington transistor pair) is
enabled to allow field weakening in response to accelerator position.
At this stage, the key can be released to the "run" position.
Shutdown is all relays de-energized.
Something to consider: It would be fairly easy to design and build a
substitute controller with an Arduino, some instrumentation-grade
op-amps and a couple hundred lines of code. The days of using
TTL/CMOS discrete components to build logic and control circuits is long past.
Overloaded yet?
At 08:50 AM 5/25/2019, you wrote:
Awesome, thanks so much for the information. This is a great start towards
making this thing work. When I was in college, one of my computer science
professors explained that the people in the factory put the magic smoke into
the electronic components, and it is our job not to let the magic smoke out.
I have taken this to heart when working on electric stuff like this which I
know very very little about. Thus I am unwilling to just put voltage to a
component like the motor and see what happens. Normally, when I go to work
on something I have a massive technical library to draw upon, but in this
case, I am starting out in the dark and this has shined some light.
On the operational characteristics of this motor, by the field having full
voltage at stop (or just more voltage than the armature), it overpowers the
armature and creates drag buy forcing the system to generate electricity,
and when the armature has more voltage it uses the battery power to turn.
Is this correct? Not that it necessarily helps in getting it running, but I
like to know how/why things function.
I turned the key on, and to the start position a couple times, but I got
nothing to indicate than any electrons were flowing anywhere in the system.
I figured that the start position was just a relic of a standard ignition
switch. I did not have a 12v battery hooked up, which is likely one reason
things didn't work. I had scavenged every easy to grab battery around the
shop, and I had 10 12v and 2 6v strung together in the battery tray, and
none left over for the vehicle. I will scrounge up a couple more batteries
to make this work.
I tried to take the cover off the motor, but to didn't want to pop right
off. I will play around with that some more. The brushes are not stuck to
the armature, as I have made it turn manually, but I don't know that they
slide freely in their housings.
One thing that I read about this specific system is that it has regenerative
braking from 43mph down to 30mph, and another source said that it has
regenerative braking down to 0mph. The top speed is 43mph. Either way, it
is not all that important, as it works one way or the other. The brake pads
show very little wear, but the vehicle only has 11,000 miles on it. An
interesting thing with it is that there is no vacuum brake booster like is
seen on every other VW with disc brakes. That makes more sense with the
regenerative braking.
I will play around with this more next week and report back on my
progress.
--
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