Quote:
Originally Posted by Christ
So if at 120v 20A the motor spins 500RPM and creates 50lbft TQ, and I switch to 240V 10A, It will create the same 50lbft, but at 1000RPM?
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I don't think it works that way. I've been thinking about this all day! It has given me a headache, and here's what I think I know:
The Torque-RPM curve is approximately a straight line for a DC motor. At 0 rpm, the torque is highest, and at max rpm, the torque is 0.
At 240v, the MAX rpm is 2 times the MAX rpm at 120v. Also, at 20 amps, the MAX torque is 2 times the MAX torque at 10 amps. So, I attached a picture of the graph of the torque-rpm lines for 120v @ 20amps and 240v @ 10amps.
In the picture, w120 is the max rpm at 120 volts, and T10 is the torque at 10 amps (2*T10 is the MAX torque at 20 amps and 2*w120 is the MAX rpm at 240 volts). Their rate of rotation and torque are the same at one point, when the RPM is 2/3 of w120 (algebra! Find where 2 lines cross! hahaha!)
There are some torques that the higher voltage setting just can't match, and some speeds the higher current setting can't match.