Question 535Electricity & Electronics - Assistant Engineer

The correct answer is B) 100 rpm. The synchronous speed of a three-phase synchronous motor is determined by the frequency of the supply power and the number of poles in the motor. The formula to calculate the synchronous speed is: Synchronous speed (rpm) = (120 x Frequency) / Number of poles In this case, the frequency is 20 Hz and the motor has 24 poles. Plugging these values into the formula: Synchronous speed (rpm) = (120 x 20) / 24 = 100 rpm The other answer choices are incorrect because: A) 50 rpm is too low for a 24-pole motor operating at 20 Hz. C) 200 rpm is too high for a 24-pole motor operating at 20 Hz. D) 240 rpm is also too high for a 24-pole motor operating at 20 Hz.