NEIEP Mechanics Practice Exam

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Prepare for the NEIEP Mechanics Exam with multiple choice questions, hints, and detailed explanations. Ace your test and advance your career!

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What does synchronous speed refer to in an induction motor?

The maximum speed of the rotor
The speed of the stator's magnetic field
The speed at which torque is generated
The speed when the motor is under load

The correct answer is: The speed of the stator's magnetic field

Synchronous speed refers to the speed at which the stator's magnetic field rotates in an induction motor. This speed is determined by the frequency of the electrical supply and the number of magnetic poles in the motor. Mathematically, it can be calculated using the formula: Synchronous Speed (RPM) = (120 × Frequency in Hz) / Number of Poles. Understanding synchronous speed is crucial because it defines the upper limit of rotor speed in an induction motor. The rotor cannot reach this speed due to the nature of induction motors, which rely on slip to generate torque; thus, the rotor always operates at a speed slightly lower than synchronous speed when the motor is running under load. This relationship plays a significant role in the performance characteristics of induction motors.