Variable Frequency Drives

Frequency is _________ to the motor speed.

• directly proportional

• indirectly proportional

• unrelated

What is the nominal speed (rpm) of a 2-pole AC motor in the US?

• 60

• 120

• 3600

What is the benefit of a mechanical speed reducer?

• It reduces torque while increasing speed.

• It reduces speed while increasing torque.

• It increases torque while increasing speed.

Adding more sets of poles is another way to reduce the speed of AC motors.

• True

• False

• I don't know.

Which of the following are NOT a disadvantage of the mechanical speed reducer?

• Require lubrication

• Subtle to vibration & noise

• Suitable for distance shafts

• No flexibility

Which of the following is a disadvantage of adding more sets of poles to an AC motor?

• Simple to design

• Extremely fine control

• No fine control

The biggest advantage for utilizing a Variable Frequency Drive is that you can control the speed and voltage supplied to AC motors.

• True

• False

• I don't know.

The Variable Frequency Drive (VFD) can easily accommodate new speed and torque requirements for the AC motor.

• True

• False

• I don't know.

Because of their flexibility, VFDs are widely used in Industrial and Commercial applications.

• True

• False

• I don't know.

The VFD varies the frequency of the voltage to the AC motor which controls the speed of the AC motor as needed.

• True

• False

• I don't know.