Most of the golf cart companies are switching to Separately excited motors. The H bridge now only needs to pump out 10Amps or less to the field and you have significantly less silicon in the H bridge. The armature circuit on most low cost controls is anywhere from 225 to 275 Amp current limit. You can probably get by with 6 or less TO-220 MOSFETS and 4-6 Schottky diodes for the freewheel current. The other advantage of the shunt system is it's relatively easy to regen and you have a broader Torque-speed curve using an inexpensive control.
Rod hower.iwarp.com/photo.html Hi Everyone, I've been asked by a client of mine to design an electronic motor controller for some low-ish current (30A peak) 36 or 48 volt motors and I got to thinking that I could probably design it so I can "add more silicon" and get it to the stage were it could drive golf carts, it would be a more useful product. The problem is that I can't seem to find any specifications on what golf cart motors consume.. I see that they run on between 36 and 48 volts, but I've not seen any current specs. Can anyone point me at some reliable information on this? I'm looking at a Microprocessor controlled full H-Bridge system with a serial interface for programming various parameters like accel and decel rates, speed limits, and even be controllable from the serial port. It would "normally" be operated by a pot-box. It will support regen and be able to limit it so that it doesn't "over charge" the battery pack.. Running some numbers on various MOSFETs I would expect I can get a 100A continuos rating without too much trouble (and a good heatsink). Would that be enough? I'm figuring I can get away with just one 80A MOSFET per leg for the 30A version, and go up to 3 or 4 per leg for the high current one (different MOSFETs, but that isn't a bit problem). I haven't done a high current H-bridge before, but I've been doing a lot of reading, would anyone familiar with them be interested in critiquing my "rough design"? Is there an email list for this kind of thing? Thanks for your help guys.. Cheers, Ash. --- Ashley Roll Digital Nemesis Pty Ltd www.digitalnemesis.com Mobile: +61 (0)417 705 718
