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BLDC motor characteristics

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waverunner

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Hello friends,
can someone explain me how to find max current and max voltage of a bldc motor 36V/500W, to selects MOSFETs that are ok for that?
Thanks
 
36V is the max voltage obviously. With know voltage and wattage you can determine that the current is about 14amps but that's it's RATED power not what it will do during a stall, the DC resistance of the coil will determine the stall current which is a value you haven't listed. I'm not sure how you would determine what the coil resistance of a BLDC motor is, aside from opening it up and using a meter. Depending on how you control the motor though and how it senses you need to keep in mind that if a sudden load is applied which causes the driving/applied voltage to be out of phase you could get much higher voltages, worst case scenario is double the voltage, and you'll want to derate from that value.

Those are just theoretical considerations, someone else here probably has more practical advice to give (at least I hope so)
 
Thanks for the answer. 36\v is the max.. The motor is in star mode (Y) and the resistance is 0,23 Ohm of each phase. The i design a 6 MOSFET bridge to control the motor with Texas UC3525. The first thinking was that is 13,88 A, but i confused, cause every moment are 2 of 6 Mosfet ON, and 2 phases active...
 
You might want to be careful there. .23 Ohm's for a coil is 140amps possible pulse current from a 36v source, during a stall situation. Stalls with a BLDC are more determined by their controller than the motor winding values though. This is why the controller for a BLDC will amost always blow long before the motor.
 
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hm.. ok.
I think that is big problem.
I would like to calculate the max voltage in Vds of Mosfet and the max current who pass it.
 
thanks ..
can you explain me how can i calculate to find that??
power (watts) = V X A A = P/V A = 500/36 = 13.888888888888889 amps
 
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