CPM CPM - Certified Plant Mechanic Electrical Systems and Controls 3

Question 1

What does VFD stand for in industrial motor control?

Accepted Answer

Variable Frequency Drive

Answer

A VFD (Variable Frequency Drive) controls motor speed by varying the frequency and voltage supplied to the motor.

Question 2

Which output parameter does a VFD primarily adjust to control the speed of an AC induction motor?

Accepted Answer

Output frequency

Answer

Motor speed is proportional to supply frequency; a VFD changes output frequency to achieve the desired RPM.

Question 3

What does PLC stand for in industrial automation?

Accepted Answer

Programmable Logic Controller

Answer

A PLC (Programmable Logic Controller) is a ruggedized industrial computer used to automate electromechanical processes.

Question 4

What is regenerative braking in a VFD drive system?

Accepted Answer

Returning kinetic energy back to the power supply during deceleration

Answer

During regenerative braking, the motor acts as a generator and the VFD can feed energy back to the supply bus, improving system efficiency.

Question 5

What is the purpose of the acceleration and deceleration ramp settings in a VFD?

Accepted Answer

Control the rate of speed change to protect the motor and mechanical components

Answer

Accel/decel ramps define how quickly the VFD changes motor speed, reducing mechanical shock and inrush current on the driven equipment.

CPM - Certified Plant Mechanic Practice Test