DC input to VFD for EV

To go from DC to AC , the unit is called an inverter. You can get them most anywhere.

Why not stick with a dc motor?

Its more efficient and can be controlled probably just as easy...

John.

I think you are right, but a typical controller for an EV does all sorts of things above and beyond a simple VFD.

For traction DC motor is most suitable and there are motors designed to operate from batteries.If u still want to got through the route of VFD and AC motor it can be done but may not be economical and suitability of standard three phase motor is a big question mark even though ac motors are used in traction now a days but not thje one's u are talking about.They are specially designed.

As others have said, it is not the best use of technology, but if you are wanting to use off-the-shelf industrial components then there is no reason it will not technically work. I know of several people who have done this for experimental or "proof of concept" purposes. ABB did it on an electric race car, there was a link in this site to it somewhere.

I know one guy who did it just for fun on his garden tractor because his neighbors had an injunction issued against him for mowing his lawn too early on Saturday mornings. So he converted it to electric power like this and mowed silently real early. That way they never saw or heard him, they just noticed that his lawn was mowed. He did it just to mess with their minds.

Any VFD is technically capable of having DC connected directly to it and bypassing the rectifier section. Some make it easier than others by actually providing terminals for this, some do not, so on those you would need to disassemble them and probably solder to the DC bus. Not advisable unless you got the VFD for free.

Then you will also need a means of dissipating any regenerative energy that comes back from the motors when coasting or stopping. Some of it can be pumped back into the batteries via their charging circuit, but a standard VFD will not have that so you need that as well. The rest must be pumped into braking resistors, sized for the duty cycle and energy capacity you need for effective electric driving. The circuitry and intelligence to do that correctly can be daunting.

Then you have to deal with the power-to-weight aspect of off-the-shelf industrial AC motors. You will end up consuming a lot more energy just having the motor haul itself around than if you used a specifically designed EV motor.

Lastly you have to deal with the voltage. Off-the-shelf industrial AC 3 phase motors are not going to come with any less than 208V windings, 230V if you are wanting to use IEC motors. This means that at a minimum, you will need to have 300VDC available (325VDC for IEC). Assuming 12VDC cells, that is 25 to 27 batteries in series, better to go higher to allow for some voltage drop for range, so figure 35 minimum. Then you start with whatever parallel configuration you will need to attain the amp-hours to get the HP and range you want to have available. Lots more weight to haul around. You start running up against the laws of diminishing returns very quickly. Li-ion battery systems are better in that aspect, but if you don't know what you are doing with the charging circuit, steer clear of that (pun intended).

Other than that, have fun experimenting!

For small EV applications VFD's are a good idea now days. Many have direct DC to 3ph AC conversion, with many motor control features (even on the basic models) and are fairly inexpensive and easy to implement and use without the need for modification. By small EV I mean very light car or smaller.

AC Tech and ABB do a nice range.