Need help with electric car PWM motor control circuits.

[XmodAloy]

Hello, I am planning on doing a electric car conversion, and want to do most of the circuitry myself to save money (don't have the $1000 or more for the motor controllers, saving that for batteries). I have found several schematics that look useful, but I do not know if they fit my criteria. I have already bought a motor, it originally came off of a forklift and was rebuilt by the seller. The specifications of the motor are: DC, 36 volt, individual stator and armature windings, current draw of around 600- 800 amps.
I know this is a little higher current, lower voltage motor than most EVs are using, But I would like to try it anyway.

Some of the schematics I am looking at: **broken link removed** The Using MOSFETS Website: H-bridge using P and N channel FETs

I am planning on using two separate ESCs, one smaller H Bridge one for the stator windings (100 amps or so, and H Bridge ESCs are reversible, so I reverse the stator field to go backwards) and a larger non-H Bridge controller for the armature (700 amps or so).

I figured Pulse Width Modulation would be the way to go, since I see a lot of other circuits using it, but if I am wrong, please correct me.

If anyone can give me some good schematics for the armature circuit and some part numbers, your help would be greatly appreciated!

 

[shortbus=]

I don't know if you have been here; I want to build an EV! Where do I start? - DIY Electric Car Forums

There's a ton of information there. Also you may not know that a lot of guys are going with three phase AC motors instead of DC. In general a 3PH AC motor is smaller/lighter for the same horsepower.

Some more sites;

The Electric Vehicle Discussion List

**broken link removed**

Forums | V is for Voltage electric vehicle forum

 

[tcmtech]

There is no point in having double reversible control systems. Neither needs to be H -bridge as well. If its a 36 volt motor with a 36 volt field there is also no need to put a PWM system on it. A simple set of relays to dictate what direction of current flow goes through the fields is enough.

If you are on a limited budget making it unnecessarily complicated serves no purpose or gains.
In a high power drive system simple and rugged is what is needed.

 

[XmodAloy]

Ok, maybe I wasn't as clear as I could have been, The motor I have is rated for 18 horse power and is massive (got it because it was cheap), and I was not meaning to say that both the controllers were going to be reversible, only the stator field controller was going to be reversible. I have heard that a lot of other vehicles are using 3 phase AC motors (Better known by the RC world that I come from as "Brush-less" motors, And yes, I know this is only similar in concept to an electric RC car) however, these motors are rather expensive, and I have been unable to find any cheap motor controllers for them, and as I have already bought the motor, I am sort of stuck with going DC anyway.
I have been thinking about just using a four speed (On low, On high, Off, Backwards) power limiter for the stator field coil instead of a PWM controller, and it would probably save me some money, but I don't think I could easily runn 100 amps at 36 volts through any cheap relays, I have never had much luck with relays when you try to put a lot of power through them, and they have a bad tendency to stick closed when you don't want them to.
I don't mean to be a rain cloud on my own parade, but, I don't see very many good options of how to limit the amount of current going to the stator field other than a PWM controller.
If it helps, here is a video of my motor: YouTube - Electric car motor test run.