A locked rotor test is performed on a permanent magnet DC machine with the following results:
Terminal Voltage 5 V DC
Input Current 10 A DC
Locked rotor torque. 20 Nm
a) Making suitable approximations deduce the effective rotor resistance in ohms?
b) Making suitable approximations deduce the torque constant kφ in Nm/A?
c) If a light running test was now performed with a terminal voltage of 50V DC what approximate shaft speed in rpm would you expect?
I did some calculations, however I am not sure if what I am doing is correct.
Short circuit current at normal voltage
Short circuit power factor
The Attempt at a Solution
a) V/I= R => 0.5 ohms
b)Torque = k*Ia => Torque/Ia = k = 20 N*m/10 = k = 2
c) w= k*v => 50v*2= 100 rpm
I am not too sure if these are correct, it would be great if someone can help! Thank you :)
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