180-205

How does an induction motor differ from a synchronous motor in terms of speed?

• Induction motors run slightly slower than synchronous motors

• Induction motors run at a higher speed

• Induction motors run at exactly the same speed

• Synchronous motors run at a higher speed

The speed of the rotating magnetic field in an AC motor is determined by what two factors?

• Slip speed and efficiency

• Power rating and torque

• Voltage and current

• Frequency and number of poles

What is the term used to describe the difference between the synchronous speed of the magnetic field and the actual speed of the rotor in an induction motor?

• Efficiency

• Power factor

• Torque

• Slip speed

Why are induction motors generally preferred over synchronous motors in industrial applications?

• Induction motors are simpler in construction and operation

• Synchronous motors are more efficient

• Synchronous motors offer better speed control.

• Induction motors require less maintenance

What is the main function of a variable frequency drive (VFD) in relation to an induction motor?

• To convert AC power to DC power

• To increase the starting torque

• To improve the power factor

• To adjust the speed of the motor

What is a key benefit of using a variable-frequency motor drive (VFD) with an AC motor?

• More complex maintenance procedures

• Higher operating temperature

• Increased motor weight and size

• Reduced power consumption and vibration

What is the main function of the rectifier section in a VFD?

• To convert AC power to DC power

• To control the switching sequence of transistors

• To synthesize a sinusoidal waveform

• To smooth out DC voltage

In the inverter section of a VFD, how do transistors create a rotating magnetic field?

• By maintaining a constant DC current flow

• By pulsing on and off rapidly to simulate a sine wave

• By using permanent magnets positioned around the stator

• By constantly switching on and off in a square-wave pattern

. What is the relationship between VFD output voltage and frequency according to the V/F ratio?

• Voltage is directly proportional to frequency.

• Voltage is inversely proportional to frequency.

• There is no fixed relationship between voltage and frequency.

• Voltage remains constant regardless of frequency

Why are VFDs typically not equipped with motor speed feedback mechanisms unlike DC motor drives?

• VFDs are simpler in design and don't require them

• AC motors are not inherently frequency controlled

• Speed feedback can introduce safety hazards in VFDs

• The cost of speed feedback is too high for VFDs