NEIEP Mechanics Practice Exam

At what point is the main motor field voltage highest?

1. When the elevator is ascending

2. When the elevator is leveling

3. During emergency stops

4. At the maximum load

The correct answer is: When the elevator is leveling

The main motor field voltage is highest during the leveling phase of the elevator operation. Leveling refers to the moment when the elevator is coming to a stop, preparing to align and open its doors. During this process, the control system increases the voltage to the motor fields to ensure precise positioning and smooth operation as the elevator approaches the desired floor. This increased voltage enables better control of the braking system, allowing the elevator to decelerate smoothly, making sure it stops at the correct height. In contrast, during ascending, there may be fluctuations in motor field voltage due to the varying demand for power as the elevator changes speed. In emergency stop situations, the voltage could be reduced to ensure safety and control, avoiding sudden halts or jerks. When the elevator is at maximum load, while it does require significant power, the emphasis is on maintaining speed and torque rather than maximizing field voltage. Therefore, the unique requirement for precision and control during leveling ensures that the main motor field voltage reaches its highest point at this time.