NEIEP Mechanics Practice Exam

Electrical overspeed switches must trip at what percentage of the mechanical tripping speed for cars that travel above 150 to 500 fpm?

1. 80%

2. 85%

3. 90%

4. 95%

The correct answer is: 90%

Electrical overspeed switches are critical safety devices that activate when the speed of the elevator car exceeds safe operating limits. The purpose of these switches is to prevent accidents that could occur due to excessive speed. For cars that travel at a velocity of 150 to 500 feet per minute (fpm), the standard requirement is for the overspeed switches to trip at a threshold of 90% of the mechanical tripping speed. This means that if the elevator reaches 90% of the maximum allowable speed—set by the design and mechanical specifications of the system—the overspeed switch will actuate, signaling the control system to halt the car. This proactive measure is essential in ensuring passenger safety by preventing mechanical failure or loss of control due to excessive speeds. The option indicating 90% accurately reflects the industry standard for elevators operating within that specified speed range, ensuring a balanced approach to safety without compromising performance. Understanding this requirement emphasizes the importance of careful engineering and adherence to safety protocols in elevator design and operation.