When I first decided to build an EV, I decided it was going to be a simple DC electric motorcycle.   In an effort to keep costs down, I decided on the PERM PMG-132 DC “Pancake” motor that had a good power to weight ratio and run it using an Alltraxe AXE 7245 DC controller.

The Perm PMG-132 DC Pancake motor

However, as the project morphed into something significantly larger, and more complex, the Perm became woefully inadequate.  So I began looking for other possibilities.

I looked at in-wheel motors, larger DC motors, Permanent magnet motors, brushless DC motors, and pretty much any motor available to the end user.  Needless to say, there are a lot of motors out there.

Electric Vehicle projects are a strange thing.  I started out with humble goals and ideas.  But once I got going, I found that my goals and ideas began to grow and become more ambitious.  I was (and am) spending a lot of time, money, and resources on this project, so I wanted it to be the best it could be.  I still do.  That means going with the best motor available.

That means AC.  AC motors have the best overall efficiency (they might not have as high a peak efficiency as DC motors, but their efficiency band is far wider), and they provide Regen easily along with better power bands.  AC motors are mechanically superior to other motors (no brushes or rare earth magnets) and are much less susceptible to failure due to environmental dirt & grime because they can be fully sealed.

So with this in mind, I contacted HPGC.  HPGC is currently the only outfit that supplies AC motor drive systems for the small EV market.  Talking to Brian and crew, they recommended their AC-31 setup running at 96V or 72V.   For certain reasons that I won’t go into in this post, I opted to go with the AC-31 @ 72V and a Curtis AC controller.

The HPGC AC-31 motor & controller system

Since my order was a single order for a Prototype vehicle, it took HPGC a while to get me the motor (they were swamped with a large OEM order from another company).  In the mean time, I sent the specs to Kale Kotecki at K2Metals (who was building the frame for the SPARC) and he used them to build the motor mount using a foam mockup of the motor.

The to-scale motor mockup made of foam

While this picture shows the motor mockup oriented longitudinally, that’s not how it will be mounted.  The actual mount location is directly below the rear seat (in front of the swing arm pivot) and the motor will be oriented transversely for a chain drive transmission.

The motor itself is fairly heavy (about 100 lbs), especially when compared to the original little Perm PMG-132 (which is about 25 lbs).   Of course, this motor is a lot more powerful and superior in just about every way to the Perm so the weight is a necessary trade off.  I don’t want to have to worry about the motor overheating & failing because it’s overloaded.  The Perm would have been severely overloaded.   The goal for the SPARC XEV is to be a capable highway vehicle.  That means traveling for extended distances at 60+ mph without fear of burning out the motor.  The AC-31 should give very good performance and dependability in that arena.

Eric