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Originally Posted by MPaulHolmes
On a bench. I do have a golf cart with a DC motor inside, so a good choice for me would be a motor I could mate to the transmission.
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What model golf cart? I have not seen used golf carts with AC as yet. Perhaps a forklift? They have been running AC for a few years now. I think HPEVS started out with golf carts and fork trucks ...
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I have a 3 phase 12v BMW alternator that Otmar let me borrow. It doesn't have an encoder.
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The alternator should take a fair bit of current. My car alternator outputs over 200 amps. What do the specs for the alternator list?
Bolting an encoder to whatever you are using as a load (like maybe a generator head?) may work OK. I have not tried this type of thing as yet.
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I also have a 208vac 3/4HP I think. It even has an encoder, but I don't know if I can push enough current through it to actually test the FOC code.
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3/4 HP is maybe 3 amps full load current. If you stall the motor by coupling it to a load that is too large for it to move you could get between 6 and 8 times your full load current when you start up your controller, push a lot of current into the motor, and heat the motor up *REALLY* fast. I would advise 10 seconds or less and let the motor cool off for at least half an hour between tests.
Why do I know this? We overheat motors to failure at my day job a lot (I call them Light Emitting Motors - LEM), when the pumps that are being driven are mechanically jammed somehow. These pumps are just start/stop, no controller. The belt-driven ones just burn the belts off. The direct drive ones survive only if the overload blocks on their starters do their job. Sometimes they don't, or the wrong size overload was installed!
I would not be in the same room with the motor while testing if you decide to stall the motor.
Can you couple the alternator shaft to the 3/4 HP motor and use the encoder from the motor as feedback? The 3/4 HP motor (connected to a second controller) could be set to a lower speed and provide a load via regen?
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Sure I can get it to spin with a V/Hz sort of thing. Can you drive with V/Hz as the software? With an encoder, it could be pretty smart.
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Yes, you can drive a motor (and a vehicle, for that matter) with V/Hz but it is not very efficient. The motor heats up. The FOC shifts the phase Voltage and Current (so I'm told) so that you are minimizing the core losses. With V/Hz you are doing a linear estimate on a non-linear load, and the extra current you pump into the motor is dumped as heat. We use V/Hz on pumps and fans. The load varies proportional to the cube of the speed. So 1/2 speed is about 1/8 load. Running in V/Hz is simple and allows us to replace motors without 'tuning' the controller to the new motor. But it wastes a bit of power.
I have no experience with an encoder on a V/Hz driven load. As I understand it, the controller does not have the option of changing the output voltage separate from the frequency when in V/Hz?