Question

Choose the correct one. (* stands for multiplication, J represents the moment of inertia, w represents angular speed).

(a) J*d(w)/dt = Load torque – Motor torque

(b) J*d(w)/dt = Load torque + Motor torque

(c) J*d(w)/dt = Motor torque – Load torque

(d) J*d(w)/dt = Load torque * Motor torque

The question was asked in exam.

Asked question is from Dynamics topic in division Dynamics of Electrical Drives of Electric Drives

Answer 1

Correct answer is (c) J*d(w)/dt = Motor torque – Load torque

The best I can explain: J*d(w)/dt = Motor torque – Load torque is the dynamic equation of the motor. Motor torque will try to aid the motion of the motor, but load torque will oppose the motion of motor that’s why it subtracts in the equation.