3-phase IM DTC controller build

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Stiive
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3-phase IM DTC controller build

Post by Stiive » Wed, 24 Oct 2012, 20:56

BigMouse wrote: I would really love to have a big fan like that as a load.


Haha i hate the thing... but it has proved useful for testing.

Guess i'll have to cut it off in the end, then you should come pick it up :P
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3-phase IM DTC controller build

Post by woody » Wed, 24 Oct 2012, 23:11

Stiive wrote: Very boring proof of the controller working :P

http://www.youtube.com/watch?v=flm-LZzXT70&feature=plcp
You can put youtubes in as

Where does the inertial energy go if you don't have capacitors / batteries to take it?

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Post by coulomb » Thu, 25 Oct 2012, 03:06

woody wrote: Where does the inertial energy go if you don't have capacitors / batteries to take it?

If you're not careful, it increases the bus voltage basically without limit.

When experimenting with a circuit that was producing DC into a resistive load, I ended up with 90 VDC across the DC bus, till I hurriedly switched it off. The adjustable power supply was set for around +-14 VDC (28 V total), and I was turning the DC bus voltage up and down. The power supply is rated for 60 V, so I was lucky not to fry it. It took me a while to figure out what happened. [ Edit: the bus capacitors are rated for 750 VDC, so that fortunately wasn't an issue. ]

I heard Stiive mention that he would not attempt a DC brake, likely for that very reason. But I still think that with regen, the same thing could happen. His circuit didn't seem to be very aggressive with regen.

Any comments, Stiive? Were you watching the DC bus voltage at all?

[ Edit2: I remember how it happens now. The output of the inverter, though only feeding a resistor, has an LCL filter, so the 25 uF of the filter's C was slowly pumping energy into the 7mF of DC bus capacitance. I say slowly, but it wasn't quite slow enough for me at the time. Image ]
Last edited by coulomb on Mon, 29 Oct 2012, 09:08, edited 1 time in total.
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3-phase IM DTC controller build

Post by Stiive » Thu, 25 Oct 2012, 03:53

woody wrote: Where does the inertial energy go if you don't have capacitors / batteries to take it?


Yeh I have some DC capacitance, about 20uF per phase acting as a snubbers. They are on the underside of the board and why the board doesn't sit on the ground.
So they are probably absorbing most of the current from stopping the unloaded motor, but any excess would go back into the laptop chargers, and they probably dont like that :P That's why i didn't want to stop the loaded motor.
I have tried spinning the load as fast as possible, disconnecting the laptop chargers and then trying to stop the motor, but it didnt seem to work. I think i used the small amount of energy in the caps up before i commanded the DC injection, which means the motor was no longer fluxed and therefore couldnt produce regen...

coulomb wrote: Any comments, Stiive? Were you watching the DC bus voltage at all?

Not on a multimeter, just my ADC output on the LCD.
I have a new isolated power supply to play with and add into the mix, that should provide some fun tomorrow.


Tonight I tested 2 random motors on a dyno and went to Melbourne Electric Vehicle Interest Group. Hopefully someone's gonna lend me some batteries and a motor to blow up :D
Rgds,
Stiive

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3-phase IM DTC controller build

Post by Stiive » Thu, 25 Oct 2012, 04:13

coulomb wrote:
His circuit didn't seem to be very aggressive with regen.
It's not aggressive because I have nothing to absorb that energy. There is nothing in my code limiting the regen
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Post by Johny » Thu, 25 Oct 2012, 14:53

Sttive I have a 2.2kW 4 pole sitting around doing nothing if it helps. I'd like it back at some stage in the future. I'm in the Eastern suburbs of Melbourne.

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Post by Stiive » Thu, 25 Oct 2012, 14:57

Johny wrote: Sttive I have a 2.2kW 4 pole sitting around doing nothing if it helps. I'd like it back at some stage in the future. I'm in the Eastern suburbs of Melbourne.


Hi Johny, yeh that could be useful.
First I need a more powerful supply. Hopefully getting my hands on some old batteries.

So far i'm running my 1.5kw motors using just 100W, a bigger motors not gonna help atm.

I'm NE suburbs. Did you goto the ATA MEVIG meeting last night at Swinburne?
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Post by Johny » Thu, 25 Oct 2012, 15:05

Stiive wrote:I'm NE suburbs. Did you goto the ATA MEVIG meeting last night at Swinburne?
Um, no. I'm not real good at meetings - nuff said.

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Post by Stiive » Thu, 25 Oct 2012, 15:10

Johny wrote: Um, no. I'm not real good at meetings - nuff said.
Ah i c, the type to get drunk and strip naked? Best you stay at home then Image
Its a nice crowd of DIY people though, good for networking, ideas and selling/buying EV parts.
I don't actually go often myself, though i'll prob present details and a demo of my controller in one of the next meetings.


Anyway, I'll let you know how I go with sourcing some batteries... looks like a got a few leads atm.

I'm intent on making plasma inside my 1.5kW motor, or blowing up some IGBTs... Hopefully the former, though I do have 9 spare IGBTs.
Rgds,
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3-phase IM DTC controller build

Post by Stiive » Thu, 25 Oct 2012, 16:06

Stiive wrote:
coulomb wrote:
His circuit didn't seem to be very aggressive with regen.
It's not aggressive because I have nothing to absorb that energy. There is nothing in my code limiting the regen


Just did some regen tests, from a voltage of 80V, i get upto about 160V of regen from the unloaded motor. All my stuffs rated for 650V+ so i'm not phased.... pun intended :P

Obviously bigger capacitors would take longer to charge and not climb so high. Also output of the transformers prob have some diode protection to stop current being fed back in.
Rgds,
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Post by Stiive » Fri, 26 Oct 2012, 03:36

Nice, just got lent a battery pack.
Let the testing begin!
Rgds,
Stiive

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Post by Stiive » Sun, 18 Nov 2012, 04:25

Finally blew my first IGBT! Had to disable the current limit completely, and it didn't actually take that long commanding full positive torque, then full negative torque with no ramp. I wasn't even keeping tabs on the temp or current because I thought it would take longer. I also didn't have airflow over the heatsink so that's probably why.

IGBT was a complete short between gate, emitter and collector. System shut down safely with a small spark from a cap discharge on the gate driver since the gate shorted. After the IGBT was removed, everything is working fine again.

I still have 9 IGBTs spare, but unfortunately when unsoldering the stubborn blown IGBT, it ripped up the PCB gate trace with it, which sucks. I could solder straight onto the gate leg of the new IGBT as a workaround, but I think this is a good opportunity to now swap to some larger IGBT bricks as i'm happy with the way its all working so far.


Also purchased a large 15kW 160L frame copper rotor induction motor. Its a beast and weighs 110kg! I'm hoping i can get 100kW+ out of it with the larger IGBTs. Have spun it upto about 6,000RPM so far and it seems pretty smooth and balanced, will go higher now I have some more voltage.


Rgds,
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Post by jonescg » Sun, 18 Nov 2012, 04:54

Stiive wrote:
Also purchased a large 15kW 160L frame copper rotor induction motor. Its a beast and weighs 110kg!


A 15 kW motor which weighs 110 kg doesn't sounds particularly impressive. I'm guessing it was rated ultra conservatively?
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Post by Stiive » Sun, 18 Nov 2012, 04:57

jonescg wrote:
Stiive wrote:
Also purchased a large 15kW 160L frame copper rotor induction motor. Its a beast and weighs 110kg!


A 15 kW motor which weighs 110 kg doesn't sounds particularly impressive. I'm guessing it was rated ultra conservatively?


As are all industrial induction motors.
Should be possible to do about 8-10x peak power. Continuous power (in an EV sense) should be more like 40kW
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Post by BigMouse » Sun, 18 Nov 2012, 14:21

Stiive wrote: Finally blew my first IGBT!


Welcome to the club! I'm impressed it took you this long. You've done far better than I have. Replacing IGBTs makes motor controller development a very expensive hobby :-(

Copper rotor in that size? Very impressive. What voltage is it? Are you planning on using it only for testing, or will it be used for something specific? Have you figured out a way to put a load on it?

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Post by Stiive » Sun, 18 Nov 2012, 14:44

BigMouse wrote:
Stiive wrote: Finally blew my first IGBT!


Welcome to the club! I'm impressed it took you this long. You've done far better than I have. Replacing IGBTs makes motor controller development a very expensive hobby :-(


Haha yeh, that's why I started off with these IGBTs before I move onto my bigger ones. I have always been set out to blow an IGBT to check the failure mode of the controller, but never (until now) had enough voltage/current available. I'll prob repeat the test if i can fix the trace before I re-enable the current limit to monitor temps and current etc. Might also be worthwhile to see how hard i can push it with some fans blowing on the IGBTs. They reckon they can hold 75A if you can keep them at 85deg, and 150A if you can magically keep them at room temp lol. I think i'll move onto some 600V 200A IGBTs that Kevin Woodhouse from Power Electronics gave me next, then onto 600V600A IGBTs and finally the 600V900A beast.
BigMouse wrote:Copper rotor in that size? Very impressive. What voltage is it? Are you planning on using it only for testing, or will it be used for something specific? Have you figured out a way to put a load on it?


Unfortunately its a 380/660V @ 50hz. Might try do a parallel conversion on it, but my last one didn't go quite as well as hoped. But lessons learned, no shortcuts this time, and hopefully more free space in the frame will allow for a good result. 380V @ 200hZ would be ideal I think for 150kW.

This was just a good find from eBay, but i also went to the SEW factory and saw their impressive range of copper rotor motors. They have them in every size it seems. I was looking at their 132 and 160 frame copper rotor motors.

The motor will be used on a bench test setup for my project. After I'm done with it hopefully I can sell it again to recoup some costs.
Perhaps someone would want to put it in an EV - I can probably negotiate to give them one of my controllers with it since it will be matched perfectly by then - I guess at the end of my project, I will have no use for them either.
Rgds,
Stiive

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Post by BigMouse » Sun, 18 Nov 2012, 15:33

If you are able to get it set up for 380v @ 200Hz, then I'm sure you'll find some interest from here, especially if you sell it with a controller.

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Post by Stiive » Sun, 18 Nov 2012, 16:04

Yeh.
Ahwel, plenty of time to look for buyers, i'll need it for atleast 6months yet.
Rgds,
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