Desertprep
1 kW
Will a 48v motor make a good 48v generator? Put another way, I am trying to find a 48v generator withing using inverters and adapters. Will a motor be efficient? They are a lot lighter than auto alternators.
Jeremy Harris said:The voltage output of a permanent magnet motor used as a generator depends on four factors; the Kv (the rpm per volt) for the motor, the motor/generator shaft rpm, the winding resistance of the motor/generator and the current being drawn by the load.
You also need to factor in the difference between the rms (root mean square) voltage from the motor/generator AC waveform and the DC voltage that you will get after rectification.
Here's a worked example for a typical permanent magnet motor:
Kv = 200
rpm = =5000
winding resistance = 0.01 ohms
Current = 20 amps
At 5000 rpm this motor will generate 5000 / 200 = 25 volts with no load. With a load of 20 amps and an internal winding resistance of 0.01 ohms the motor will deliver a terminal voltage of 25 - (20 x 0.01) = 24.8 volts.
Using the above calculations you can work out the voltage you will get from any particular permanent magnet motor when used as a generator at any particular rpm and load.
Jeremy
olaf-lampe said:With a (infineon) controller acting like a step-up/step-down converter it is not that important, which voltage the motor generates.
Am I right, Jeremy?
-Olaf
Jeremy, can we tell by looking at a schematic?It does depend on how the controller implements the flyback diode arrangement - if it just uses the FET body diodes then efficiency may be poorer, but if it uses synchronous rectification then it should be pretty good. I'm not sure how the Xie Chang controllers do regen, as I've not played with it much.
Kingfish said:Jeremy, can we tell by looking at a schematic?It does depend on how the controller implements the flyback diode arrangement - if it just uses the FET body diodes then efficiency may be poorer, but if it uses synchronous rectification then it should be pretty good. I'm not sure how the Xie Chang controllers do regen, as I've not played with it much.
6FET/EB206-A-2
~KF