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5390 posts

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  # 2045168 28-Jun-2018 09:36
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Aredwood: Calculate how much current the motor would consume if it is jammed. As that is the worst case scenario current that the PWM controller needs to be able to handle. (measure the resistance through the motor when cold and use ohms law) The answer will be way higher than 60A.

PWM would work for what you want to do. But you would likely need a controller that can handle way more than 100A.

How the motor behaves under different voltage / speed / load combinations also depends on wether it is series wound, shunt wound, or permanent magnet.


Thanks for that, useful info.


My current winch (capstan) draws about 60A at the start of a retrieve, but quickly drops back to about 40A once the pick and chain are off the bottom.


In a stuck anchor situation I'm not sure, but the CB is 100A and it's never popped.  I can easily find out though - tie  rope off to the trailer and try to winch it.  Or I could look for a 150A PWM.  That said I would bypass the PWM until the anchor is close to the top.  If the anchor is stuck, it's on the bottom and the PWM won't be engaged.


Based on my previous reading, drum winches tend to be permanent magnet.


3885 posts

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  # 2045811 29-Jun-2018 01:53

Is the circuit breaker a magnetic type, thermal type, or combination? As circuit breakers intended for motors are often thermal only. Meaning that you can pass way higher currents through them for a short time. If it is a thermal type, it could still take as long as 1/2 an hour to trip with say 150A going through it.

So still best (and easiest) just to accurately measure the motor resistance. And calculate the locked rotor current. Although for really low resistance values, it is far more accurate to pass a known current through the motor, (say 5A) and measure the voltage drop across the motor. And no risk of damaging the motor / winch etc from calculating the current, instead of deliberately causing a fault.

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