Paul and Sabrina's Cheap 3 Phase Inverter (AC Controller) with Field Oriented Control

[thingstodo]

Originally Posted by MPaulHolmes

That is so awesome!!! Thank you for your meticulous tests! Do you just attach the 24v to the DC motor, and then slow it down gradually with the AC motor? I think if you hit '0' once, it sets the AC motor back to zero throttle. You could do that before disconnecting the DC motor's 24v I suppose.

Yes, I just close a contactor to the 24V circuit - no DC controller - to run the Warp9 DC motor. That's why it is a separate battery pack, and why it is such a low voltage. The unloaded speed of the DC motor is about 3600 rpm so I don't overspeed the motor if something goes wrong (like I blow a fuse on the AC)

Slow down the AC with 1<ENTER> on this firmware. Using a 20 turn pot will be more convenient but likely less accurate!

I could also kill the 12V to the AC controller after the AC Controller brings the AC motor to a stop, before it starts to accelerate in reverse.

Looking forward to the firmware that recognizes the change in direction. I think I read somewhere above that you would add a couple of lines of code so that a car would not accelerate in reverse at a stop light

[MPaulHolmes]

Originally Posted by thingstodo

Looking forward to the firmware that recognizes the change in direction. I think I read somewhere above that you would add a couple of lines of code so that a car would not accelerate in reverse at a stop light

It's not a bug, it's a feature. haha

By the way, I've finally committed to a particular configuration for the cheap AC controller. It's really targeted toward the 50kW range. I found some 900v 50uF caps for $13 each. I can fit 7 or 8 of them depending on how they are arranged on the board. And they have some very nice 1200v TO-247 super and TO-264 PLUS igbts that are pretty affordable, that can handle 50 amps RMS easily. So, here's what I'm thinking. Assume people are willing to put, say, 350v worth of smallish batteries in their car, and then they can boost it to 700v. Then, the power and other stuff is as follows:

this crap was wrong before...  See below.

[Astro]

Paul, boosting the DC to 700v, would that mean the A/C output of the controller would be 700v peak to peak or 1400v peak to peak?
What is a normal maximum A/C voltage for the average 3 phase A/C industrial motor?

[MPaulHolmes]

It would be -700 to 700 peak to peak. I'm not sure what a normal 3 phase motor can do. Maybe 480vAC line to line is pretty normal I think. So, 277vRMS line to neutral, so a DC bus of around 392v. I'm sort of thinking of those 650v motors that are at junk yards.

[thingstodo]

Originally Posted by MPaulHolmes

So, 50kW for around $350 in parts and no precision drilling. Everything can be done with a hand drill.

Sign me up!

That's a perfect size for the WIKISPEED Comfy Commuter Car (C3).

And for the golf cart-like UTV that I have on my project list.

Do you need some up-front cash for procuring parts?

[thingstodo]

Originally Posted by Astro

Paul, boosting the DC to 700v, would that mean the A/C output of the controller would be 700v peak to peak or 1400v peak to peak?
What is a normal maximum A/C voltage for the average 3 phase A/C industrial motor?

As usual, 'normal' is subject to interpretation

460V US three phase is 'nominal' 650V peak to peak, but the motors will take the 480V that is the actual output of the transformers, plus 5% easily, and 10% without damage. So 528VAC with peaks around 750V. Many 460V motors can also be wired for 230V from the motor junction box. This has been used by EV'ers for some time.

Canadian 575V is actually about 600V out of the transformer, plus 10% is 660VAC with peaks around 930VDC. The DC Bus trips on over-voltage at around 1000 VDC .

European 690V I have less information on. The DC bus trips at about 1100VDC, maybe 770VAC

As for the peak-to-peak being doubled .. that makes sense but that's not what I have seen. I'd need to look into why .. but these are the voltages that I see in equipment.

[MPaulHolmes]

Michael, is there a voltage on the 3 phases when the AC motor is spun up to 3600RPM by the dc motor, but the AC motor controller is off? Or if the AC controller's bus cap is drained to zero, and then the DC motor spins up the AC motor to the 3600RPM or whatever it was, does the AC bus cap fill up to some point?

[MPaulHolmes]

Oh dear, I made a mistake in my figgerin'. I was thinking I had line to neutral voltage from the DC bus, but it was line to line voltage. I better go re-figger and see what happens. haha

Crap, so the 3 phase bridge can make a LINE TO LINE voltage of -DC Bus to +DC Bus. So, the LINE to NEUTRAL voltage can go from -DC Bus / sqrt(3) up to +DC Bus / sqrt(3). So, the 3 phase power is then...

power = DCBus / sqrt(3) * peakPhaseCurrent * sin(0) * sin(0) + DCBus / sqrt(3) * peakPhaseCurrent * sin(0) * sin(0) + DCBus / sqrt(3) * peakPhaseCurrent * sin(120deg) * sin(120deg) + DCBus / sqrt(3) * peakPhaseCurrent * sin(240deg) * sin(240deg)

power = DCBus / sqrt(3) * 1.5 * peakPhaseCurrent
power = DCBus * sqrt(3) / 2 * peakPhaseCurrent
power = DCBus * sqrt(3/2) * rmsPhaseCurrent

So, after the boosting, let's say we have a 700v DC bus, and 50ampRMS phase current.  That means:
power = 700V * sqrt(3/2) * 50ampRMS = 42866Watt. 

So, the DC bus current is sqrt(3/2) * 50ampRMS = 61Amp
So, the battery bus current is 122amp, so the current through the inductor would be 122amp.  

The RMS current in the boost switches is 3 times the rms phase current, so is 150amp.  At the moment, there are 2 high and 2 low boost switches, so they would have to do 75ampRMS each.  Maybe there should be 3 high and 3 low.

[postmann2002]

Hello,
I'm a long time reader here in ecomodder... and especially interested on this thread.
I'm from Germany, so sorry for my bad english.

A few years ago I had the idea to build an electric car and I collected some AC-Stuff for this project. But due to lack of time I give it up.
Maybe I will continue this idea of a selfmade-electric-car in a few years more, when my son becomes 18...
But, if someone is interested to buy it, I will sell it.

I have some electric components from a 10t Hybrid-Bus for sale:

Motor/Generator PMSM/BLDC 1FV5139 85kW

2 x Driver-Boards from Elfa-Duo-Inverter
(one Driverboard is damaged (two of eight Driver-circuits are smoked by a shortcut or overcurrent... the corresponding two IGBT's were also damaged).
The Bards have also onboard a Isolated Voltage measuring circuit and connectors for two amp-sensors and one Temperature-Sensor (temperature-control of IGBT's)
4 x Big Capacitors Epcos 2100µF 385V (in the original Inverter were two in Series... so 770V rated)
6 x Big IGBT
2x Current-Sensors
Temperature-Sensor
Brainboard (I don't know if someone can reuse it)
Some Stainless-Screws
Multilayer of stainless metal-sheets with Isolators (Busbars and Phases U, V, W)

Throttle (original from the Hybrid-Vehicel)

IMA Battery NIMH 144V and 6,5Ah (Honda Insight) capable of 10kW (maybe more for shorter periodes) for experiments.
Selfmade Charger (350mA)

all together 3000€ pick up

I think, that this combination "Paul and Sabrina's Cheap 3 Phase Inverter" with my stuff would be a easy way for somebody who has time and knowledge.

I wrote to less posts here, so I can't attach pictures.
Please contact me if you are interested.

Regards Peter

[thingstodo]

Originally Posted by MPaulHolmes

Michael, is there a voltage on the 3 phases when the AC motor is spun up to 3600RPM by the dc motor, but the AC motor controller is off? Or if the AC controller's bus cap is drained to zero, and then the DC motor spins up the AC motor to the 3600RPM or whatever it was, does the AC bus cap fill up to some point?

There may be some residual magnetism left in the rotor ... that will generate some voltage of some sort ... I will check.

In an ideal world - there should not be. But we don't have access to that IDEAL world.