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

[NiHaoMike]

Originally Posted by dcb

Well, to Jacks point, it still will not be as simple or efficient a circuit as rewinding a motor for the desired voltage. I would definitely consider a DIY or shop based rewind before converters. adjusting the cell count in the pack may be an option as well.

Toyota had the option of winding the motors for whatever voltage they wanted, and they decided to go with higher voltages. In fact, they initially directly used battery voltage, then went to 500v and now 650v. I'm sure there's a good reason for it.

I think it would be easier to build a boost converter than to rewind a motor. But if you know how to rewind a motor, you can repair one with bad windings. Then replace the bearings and it is practically a new motor!

[jackbauer]

I'm not against any of the ideas here just looking at the options. What the revolt controller and forklift motor combination has done for dc conversions can be done for ac. We do however need to be careful of the project heading off into the realm of the fantastic and then not being practical for most people. I've seen quite a bit of that on other ev forums.

One of the big advantages of ac is direct drive and high top end rpm. So can industrial motors fit that bill? I've watched ben nelson's videos of the dodge neon ac conversion with interest. To be honest thats what i thought about doing many years ago when i first got bitten by the ev bug. I think that a lot of the problems being encountered with that project are down to the limitations of the industrial drive and the use of a 4 pole motor instead of a higher rpm 2 pole unit. Interestingly US spec baldor motors of the type used in the neon are available in europe as they are used in phase converters.

[MPaulHolmes]

Here's what I was thinking: Just have a 3 phase inverter with field oriented control that is around $350 with Ebay IGBTs. Make a kit out of it, with all the parts in it. I think there will be MUCH less milling and drilling and etching since you just bolt the dang igbts to the heatsink. The code for the inverter software has number of poles as a variable. Just make it user-configurable. No big deal. So, if you get a super fancy Tesla-like AC motor, then that's great! Run that sucker at 10,000-15,000 rpm! And if you get a pile of crap AC induction motor from Ebay, maybe the top RPM will be 4500 or so. Then, you would have all the torque control of a DC motor and similar rpm range, but with regenerative braking.

I think a kit, or at least a very detailed pdf of step by step assembly would help a lot in actually letting someone actually make something.

[jackbauer]

I'll definitely buy it. No question. I'll get some prices from the rewind guys locally to see what would be involved in rewinding to a lower voltage. I seem to remember someone on the australian ev forum re configuring the poles of a motor to run at a lower voltage. I'll try and find the link.

[jackbauer]

The Australian Electric Vehicle Asn: Changing an induction motor voltage

[Christ]

Did someone say "Bolt together?" I can do that!!!

I'm interested!

[Christ]

Originally Posted by NiHaoMike

Toyota had the option of winding the motors for whatever voltage they wanted, and they decided to go with higher voltages. In fact, they initially directly used battery voltage, then went to 500v and now 650v. I'm sure there's a good reason for it.

I think it would be easier to build a boost converter than to rewind a motor. But if you know how to rewind a motor, you can repair one with bad windings. Then replace the bearings and it is practically a new motor!

I think it's just a matter of higher voltage requiring less amps to do the same work?

[mrbigh]

Originally Posted by MPaulHolmes

Here's what I was thinking: Just have a 3 phase inverter with field oriented control that is around $350 with Ebay IGBTs. Make a kit out of it, with all the parts in it. I think there will be MUCH less milling and drilling and etching since you just bolt the dang igbts to the heatsink. The code for the inverter software has number of poles as a variable. Just make it user-configurable. No big deal. So, if you get a super fancy Tesla-like AC motor, then that's great! Run that sucker at 10,000-15,000 rpm! And if you get a pile of crap AC induction motor from Ebay, maybe the top RPM will be 4500 or so. Then, you would have all the torque control of a DC motor and similar rpm range, but with regenerative braking.

I think a kit, or at least a very detailed pdf of step by step assembly would help a lot in actually letting someone actually make something.

Really, I concur with Paul's concept a 100%.
If Curtis Manufacturing Co. come up to the market with a AC introductory motor controller for under 1600, how could we not make a controller Kit for the same application at 1/4 of their price with top notch technology?
Paul, have you narrowed down the selection of IGBTs for the controller prototype yet?

[NiHaoMike]

Originally Posted by Christ

I think it's just a matter of higher voltage requiring less amps to do the same work?

In the second generation Prius, they put the boost converter in the front so much of the advantage was lost. If I were to design it, I would put the boost converter near the battery. (Not sure about the third generation, though.)

I think one of the main advantages is that the supply voltage can be varied so the inverter can output more precise waveforms at low speeds. Digital audio amplifiers are remarkably similar to sine wave inverters and they often make use of dynamic supply voltage to maintain their specified bit depth at low volume settings as well as to reduce switching losses.

[MPaulHolmes]

Originally Posted by mrbigh

Really, I concur with Paul's concept a 100%.
If Curtis Manufacturing Co. come up to the market with a AC introductory motor controller for under 1600, how could we not make a controller Kit for the same application at 1/4 of their price with top notch technology?
Paul, have you narrowed down the selection of IGBTs for the controller prototype yet?

I was thinking of these for a higher powered inverter:
PRX CM600HA-24H IGBT Power Modules 1200Volt 600Amp - eBay (item 350264741592 end time Dec-12-09 10:14:45 PST)

They consistently have these available for about this price. That would be $300 just for the igbts. It might be another $300 for everything else. I think it would be pretty high power though. I would rather try this first:
Mitsubishi MG400Q1US41 IGBT Module 400Amp 1200Volt - eBay (item 350264741683 end time Dec-12-09 10:14:58 PST)

As the sum of the 3 currents rotates, it makes a net current. So, if the net current is like 300amp, it's shared between several devices. So maybe it can put out quite a bit higher? I need to understand how the current is shared a little more. I just got the A/D converter working on the dsPIC30F2010, and I still have more to learn about how it all works. hehe.