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Hi,
I looked at off the shelf AC drives too and found a couple that worked all the way down to 170V DC. Because they were only rated at 1 to 3 HP, I thought they would make a good driver for external IGBT modules (minus their own high power stage). I believe this is how Eric Tischer did his Passat conversion. BTW, off the shelf AC drives with a >50 HP rating are usually rather expensive and like to be fed 460V with under voltage lockouts at >380V
Drives can move a motor in a few ways. They can do voltage and frequency variations and hope the motor will follow the commands. This is called V/F and can have some issues in vehicle applications where lots of torque is needed at close to zero RPM. The drive might command an RPM move but the motor can't deliver it at the given current so it "slips"... but the drive has no way of knowing that. Your acceleration will be less than ideal for what your motor can really deliver.
The preferred way is vector control by which the drive measures the current/flux of each phase to determine if it needs to apply more or less voltage. There are some, like the Curtis drive, that also look at the actual motor shaft to determine how fast it's moving. This last one adds complexity but it's the most accurate method.
For some time now, I've been looking at industrial motors like you suggest. I've found very nice motors that are vector rated with excellent torque curves and relatively low voltage (220V). But what gets me every time is the motor weight. A typical 50HP motor will weigh >500 lbs. I don't want to replace my 250 lbs ICE with a 500 lbs electric motor. If anything, I was hoping to shed some poundage with the swap.
JR
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