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ttoyoda 06-14-2008 01:55 PM

Variable Frequency drives with DC input? (for electric car)
VFDs for AC motor control are common items, and not too expensive. 3 phase AC motors are everywhere, easy to find used, last forever, and are very inexpensive for their HP rating.

The VFD drives I have seen all take AC input, 1 phase or 3 phase. Since the AC gets converted into DC inside the drive, it would *seem* that DC input versions would be easy (hah!) to convert from existing units, or should be cheaper to buy (due to less parts) then the original AC input versions.

Does/has anyone know/tried this or have any other information?

What would be ideal is if the VFD drive would send power back to the DC buss during regeneration instead of dumping it into load resistors, but I doubt that is possible with a standard unit.

Here are examples of VFD drives.

Thoughts? Pointers? Links?

ttoyoda 06-15-2008 11:35 AM

For anyone else searching for this info:
It is trivially easy. This application note from Hitachi shows how.

edit: regeneratinve braking is included, no extra charge.

akbnkb 01-25-2009 06:01 AM

Im trying to repiar a Powerflex 70 rated at 50 hp to test that. the only concern i have is variable acceleration rates, like when pulling out in faster moving trafic. its vary has alot of the same parts as a ac car controller but with diffrent programing. I cant believe no one has done this before. it may work out of the box but may need some programing. also im sure that auto ac controllers have more safety features, so if i do it i would have a way of disconnecting the power in case of a failure. like how on what was that? i think it was project forkenswift he used the old clutch to seperate the battery pack from the controller using those heavy duty fork lift plugs.

forever lost 02-21-2009 10:51 PM

you don't have use something as inelligent as a cobbeled together, homemade, dissconnect. just use an industrial grade contactor. a contactor is basicaly a beefy, rebuildable, confugrable, relay. what you do is use the contactor to turn on the system power. the reason for using a contactor is you can wire it to dissconnect if theres a overload and you can also wire up a master stop/dissconnect button that will kill all power. the way you do this is something called "memory lock-in". look it up, better yet pick up the book "Electrical Motor Controls for Integrated Systems" ISBN 978-0-8269-1217-6 it's an excellent book and teaches you all about contacters, single and three phase motors and a whole slew of other things electro-mech related.

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