96 volt two perm 132 in series and parallel
i am building a very fast go-cart, currently designing. i will have a 96volt battery pack. i will be having two perm 132 motors i will have them in series this way they provide lots of torque and only run at 48volts each. but i when i want more power i want to switch the motors into parallel.
my question. does anyone run their perm 132 over 72volt, even for 10secs, and have they had any problems other than overheating and the brushes wearing out a lot faster? i am just looking at this to see if i can use this as a power boost feature, for those few seconds of happiness.
thx for your help and edvice.
well, first you need to decide if you want to do batteries in parallel, or motors in parallel.
I'd recommend doing what the NEDRA guys do, and series/parallel the motors. Use a 48v system (2 48V in parallel), and start the motors in series... so each gets the full Current, but half the voltage. Then when you get to a certain speed, flip a contactor that puts them in parallel, for 48V a piece, but half the current.
The Perm PMG132 can only rotate CW at full load, so keep that in mind when planning on how to mount them. I think the Etek-RT can be run in both directions at full load but I'm not sure.
Another option is to leave the motors in parallel and use a high-amp controller. I'm doing this on my motorcycle with a very high amp controller from Logisystems. I'm trying to calculate the advantage of using series/parallel switching vs. running in parallel all of the time. In summary, I think battery resistance factors in to make series/parallel switching advantageous. Here's some of my calculations (feel free to skip reading this if you are not interested):
BTW can anyone help with the calculations?
It's kind of confusing. Consider that power = VI. V = IR determines how much current can flow for a given voltage and motor terminal resistance. And for a motor, torque varies directly with current, and speed varies directly with voltage.
Now, consider the PMG132 terminal resistance of .025 ohms. And torque constant of 1.6875 in/lb per amp. And, imagine a 0-ohm power source.
At stall, lets say you want to produce 3375 in/lbs of torque.
With the motors in series, the motor system resistance would be .05 ohms. To send 1,000 amps to produce 3375 in/lbs torque would take a voltage of 50v, and the power into the system would be 50,000 watts.
With the motors in parallel, the motor system resistance would be .0125 ohms. To send 2,000 amps to produce 3375 in/lbs torque would take a voltage of 25v, and the power into the system would be 50,000 watts. Hence, no change in power into the system and torque output from stall.
In other words, with a 0-ohm power source, there seems to be no advantage to series/parallel switching.
Now, for a .025 ohm power source, consider the following.
With the motors in series, the .05 ohms resistance plus .025 ohms would equal .075 ohms resistance of the system. To send 1,000 amps through the system to produce 3375 in/lbs torque would take 75v, and the power into the system would be 75,000 watts.
With the motors in parallel, the .0125 ohms motor resistance plus .025 ohms would equal .0375 ohms resistance of the system. To send 2,000 amps through the system to produce 3375 in/lbs torque would take 75v, and the power into the system would be 150,000 watts.
In other words, with a .025 ohm power source, there seems to be a big advantage to series/parallel switching of the motors.
It would be helpful to contact the manufacturer.
PERM MOTOR GmbH
Hopefully they have someone on staff that can speak english.
There may be possible modifications that can be done to run at a higher voltage. It is also a good idea to advance the motor timing some to reduce arcing at the brushes.
Unfortunately, I haven't been able find anyone who's run this motor at 96v. Maybe someone on the EV album, or EV discussion list did? I would search both extensively. Also search endless-sphere.com forums.
i wrote this huge long reply, it didn't post...
Anyway, the long and short of it is, at 96V, you'll be going twice the rated 48V RPM. That thing is going to FLY apart if its allowed to go full throttle.
I'd invest in a beefier motor and run it at 96V, you'll be happier, the efficiency is better, and you'll spend less on ONE motor than you would on two. Plus, the losses are 1/2. It'l handle the heat better (more thermal mass), plus its designed for higher voltages, and faster RPMs.
I've got a 20hp max, 8hp nom, 4000 rpm 72V motor i'm putting on a bike. People are putting smaller motors on and burning rubber. I've also got a go-kart with a 48V motor that has run at 72V, and it can smoke the tires.
Try looking at an advanced DC motor (A00 or K91). Good size, great performance, and made for high torque and speed applications (50ftlbs of torque).
he's got some great motors that'd be great for the kart. Take a look at the one on the bottom for $400... its an 11 or 12 inch 6.7" diameter motor that'd be GREAT for a kart.