Deck 31: Wound Rotor Motors

Question 1

In an alternating current circuit, the current limiting effect of a capacitor is called ____________________.

Answer 1

capacitive reactance

Question 2

What are the three factors that determine the amount of torque developed by a three phase induction motor?

Answer 2

Three factors that determine the amount of torque developed by a three phase induction motor are:
1) Strength of the magnetic field of the stator
2) Strength of the magnetic field of the rotor
3) Phase angle difference between rotor and stator flux

Question 3

How is the construction of the rotor different between the wound rotor induction motor and the squirrel cage motor?

Answer 3

The difference between the two motors lies in the construction of the rotor. The rotor of a squirrel cage motor is constructed of bars connected together at each end by shorting rings. The rotor of a wound rotor induction motor is constructed by winding three separate windings in the rotor.

Question 4

How is the starting current and speed of a wound rotor induction motor controlled?

Question 5

The wound rotor motor has a lower starting torque per amp of starting current than any other type of three phase motor.

Question 6

What is one advantage and one disadvantage of frequency control?

Question 7

The operating characteristics of a wound rotor motor with the rotor leads shorted together are very similar to those of a(n) ____________________ motor.

Question 8

Small wound rotor motors are often controlled manually by a three-pole make-before-break rotary switch.

Question 9

What is the principle on which frequency control operates?

Question 10

The wound rotor motor can be started in multiple steps to provide smooth acceleration from 0 RPM to maximum RPM.

Question 11

The wound rotor induction motor is often called the ____________________ motor.

Question 12

Starting circuits generally employ resistors of a lower wattage value than circuits that are intended for speed control.

Question 13

The difference between rotor speed and synchronous speed is called ____________________.

Question 14

Maximum torque is developed when the ____________________ of the stator and rotor are in-phase with each other.

Question 15

Capacitive reactance is proportional to the rotor frequency.