NEIEP Mechanics Practice Exam

In a Linear Induction Motor, what change is made to alter the direction of movement?

1. Change the speed of the motor

2. Reverse the polarity of the power supply

3. Change the phasing to the stator windings

4. Adjust the position of the rotor

The correct answer is: Change the phasing to the stator windings

In a Linear Induction Motor (LIM), altering the direction of movement involves modifying the phasing of the stator windings. This is because the operation of a linear motor relies on the interaction between the magnetic fields generated by the stator and the induced currents in the rotor. By changing the phasing, the orientation of the magnetic field can be adjusted, which effectively reverses the direction of the induced force on the rotor. This manipulation is essential since LIMs work similarly to rotary induction motors but are designed to produce linear motion. The shifting of the phasing creates a new path for the magnetic field, which leads to a corresponding reversal of the thrust provided by the motor, thus changing its direction of movement. If one were to consider changes such as adjusting the speed of the motor, reversing polarity of the power supply, or repositioning the rotor, these actions do not directly lead to a reversal in movement direction in the same way that modifying the phasing does. Speed adjustments may affect how quickly the motor moves, while reversing polarity may not necessarily create a new directional motion in the same context, and adjusting the rotor's position does not inherently alter the fundamental operation of the motor itself. Thus, changing the phasing of the stat