Electronics > Projects, Designs, and Technical Stuff
100+kW Motor Controller
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marcos_:

--- Quote from: Siwastaja on April 30, 2019, 03:08:03 pm ---
--- Quote from: Psi on April 30, 2019, 08:41:00 am ---Interesting, i always thought re-gen required some sort of extra boost step-up system to allow pulling high current out of the motor at slow speed.

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For permanent magnet motors (brushed or BLDC), just output lower PWM duty cycle in two-switch (half bridge) design. Won't work with the simplest freewheeling diode design. With a half bridge, the motor inductance simply acts as a boost converter. Draw it, you'll see it's a bidirectional synchronous buck converter (which is synchronous boost in the opposite direction). If you want to really freewheel, you turn both switches off.

For induction motors, it's fundamentally the same, but the control is, of course, a bit more complex. You need to output lower fundamental frequency than what the motor RPM dictates; this changes the sign of slip, causing it to become a generator.

For a series-wound brushed motor, regen is a different beast, but these motor types are getting increasingly rare in modern designs.

--- End quote ---

That's true, but when you are already computing a field oriented control, everything comes down to Iq/Id currents, those are DC variables, not aware of frequency information or PWM pulses, just like your foot is unaware of the fuel injection pulse width.

Wanna accelerate? Positive Iq. Wanna brake and store energy in the battery? Negative Iq. The control loop will unfold the frequency and angle details based upon data that the actual user (a foot) does not really care (instantaneous voltages, current, and flux angle) . Its same principle with PM or ACIM machines. Its a bit less intuitive when there is reluctance torque involved, but that's another story.
schmitt trigger:
Impressive!

Let's talk a bit about thermal management. The IGBT module appears to be attached to a water cooled plate. Is my assumption correct?
If so, is this plate a catalog item, or did you actually had to machine it.

Likewise the bussbars. Are they catalog items?
Dave:
As someone that works in this industry, I find it absolutely baffling that you managed to develop all of this yourself.
Amazing, keep up the great work!  :-+
marcos_:

--- Quote from: schmitt trigger on April 30, 2019, 04:54:07 pm ---Impressive!

Let's talk a bit about thermal management. The IGBT module appears to be attached to a water cooled plate. Is my assumption correct?
If so, is this plate a catalog item, or did you actually had to machine it.

Likewise the bussbars. Are they catalog items?

--- End quote ---

The coldplate is a wolverine cp3001, as thermals are critical part of the system performance. You can loose many kW just because a poorly chosen thermal path. If you use the IGBT modules NTC temperature sensor (yes the control is designed to measuse those 3 temps) its not dangerous, but if you run open loop temperature-wise you can overheat an IGBT.
https://www.microcooling.com/our-products/cold-plate-products/3000-series-cold-plates/cp-3001/


Phase bars are custom made, we have a small cnc here, its a simple piece we do in aluminum. Soon enough we'll waterjet it from copper and avoid fighting the aluminum oxidation.


--- Quote from: Dave on April 30, 2019, 06:48:18 pm ---As someone that works in this industry, I find it absolutely baffling that you managed to develop all of this yourself.
Amazing, keep up the great work!  :-+

--- End quote ---
Ha, thanks! This also stands on years worth of effort from Benjamin developing the firmware and GUI, highhopes experience in the field, arlin experience in the dragstrip and maxi's firmware skills. But yeah, super small team.
Psi:

--- Quote from: marcos_ on April 30, 2019, 12:48:40 pm ---
--- Quote from: Psi on April 30, 2019, 08:41:00 am ---
--- Quote from: marcos_ on April 30, 2019, 03:27:09 am ---
--- Quote from: Psi on April 30, 2019, 12:35:22 am ---Regenerative braking?

--- End quote ---
Sure, in field oriented control math its just changing the sign of Iq current. That commands negative torque ("regen")

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Interesting, i always thought re-gen required some sort of extra boost step-up system to allow pulling high current out of the motor at slow speed.

--- End quote ---

You use the motor windings as inductors, the circuit has already the topology to boost.

Anyway at low speeds there is not much power available, power = torque*speed so any effort spent in low speed regen performance doesn't give you much gains

--- End quote ---

Cool!

I guess my line of thinking was...
If you dead short the 3 motor windings you will get the best braking action and a massive current flow through the short.
However the voltage will be super low.  So trying to get both good braking and high voltage for charging would require a boost circuit.
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