Question 261Electricity & Electronics - Assistant Engineer

The correct answer is A) A four-pole synchronous motor under normal load. Synchronous motors operate at a fixed speed that is directly proportional to the frequency of the power supply and the number of poles in the motor. For a four-pole synchronous motor, the speed is determined by the formula: Speed (RPM) = (120 x Frequency) / Number of Poles. Assuming the same frequency, a four-pole synchronous motor will operate at a higher RPM compared to a six-pole synchronous motor or induction motors, which have variable speeds depending on the load. The other options are incorrect because: B) A four-pole induction motor under no load would operate at a lower RPM than a synchronous motor, C) A six-pole synchronous motor under normal load would operate at a lower RPM than a four-pole synchronous motor, and D) A six-pole induction motor under full load would operate at a lower RPM than a four-pole synchronous motor.