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Old 11-17-2008, 05:30 PM
Derek.c Derek.c is offline
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Default 3 Phase Motor

Since I am really new to this concept I have a question about the motor end of this . I have a 7.5 horse 3 phase motor from a lathe , Can this be used and how would I use a DC current with an AC motor . I have visited the Wiki and cannot find this info .
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Old 11-18-2008, 08:02 AM
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Default Re: 3 Phase Motor

Quote:
Originally Posted by Derek.c View Post
Since I am really new to this concept I have a question about the motor end of this . I have a 7.5 horse 3 phase motor from a lathe , Can this be used and how would I use a DC current with an AC motor.
Hi Derek,

You need an AC motor controller. This is an electronic device which is called an inverter. It takes the DC from the battery and makes a 3 phase AC variable voltage/variable frequency output to the motor. This VVVF inverter or controller not only converts DC to AC, but will control the speed and frequency. You should be able to find info on VFDs (variable frequency drives). They are quite common in industry to control speed of induction motors and are basically the same as you would need for an EV.

As far as your lathe motor, unlikely it would be suitable for an electric car. But theoretically, it could be used.

Regards,

major
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Old 11-18-2008, 06:00 PM
Derek.c Derek.c is offline
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Default Re: 3 Phase Motor

So what would be the special things I would be looking for in a ac or dc motor to use in a EV vehicle . I only ask because I am one to scrounge and find the best possible thing for the least money but I need to know what I am looking for .
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Old 11-18-2008, 06:10 PM
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Default Re: 3 Phase Motor

You should read through the thread about picking a forklift motor to get an idea of how to do an inexpensive EV.
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Old 11-20-2008, 06:44 PM
Kirk_Wallace Kirk_Wallace is offline
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Default Re: 3 Phase Motor

I have done some CNC conversions using VFD's to run 3-phase spindle and coolant motors. eBay VFD's have been inexpensive and have worked well. One issue that has come up, has been low speed torque. Most VFD's can be tuned to improve low speed torque, but usually, I have to allow for a practical range starting at 30% of full motor speed. Also I have had a hard time running spindle motors above 60 Hz because they aren't usually balanced very well. This is frustrating because the VFD's I have can go up to 400 Hz. It would be nice to have the increased range. The higher frequencies will also produce more heat, so even if a motor is well balanced, there may still be a significant RPM limit.

VFD's vary in how they operate. I believe some may be able to use DC on their inputs, but some won't.

Bottom line,I think the low speed torque is the deal breaker for VFD's with 3-phase induction motors on EV's.

I could be wrong, though.
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Kirk
http://www.wallacecompany.com/machine_shop/
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