Deck 30: Braking

Question 1

One method of providing plugging control is with the use of an automatic timed circuit.

Answer 1

True

Question 2

Plugging is used with direct current motors more than with three phase squirrel cage motors.

Answer 2

False

Question 3

Mechanical type brakes cannot hold a suspended load.

Answer 3

False

Question 4

How is dynamic braking for a DC motor accomplished?

Question 5

Mechanical brakes can be obtained in two basic types: drum and ____________________.

Question 6

Why is dynamic braking sometimes referred to as magnetic braking?

Question 7

Dynamic braking for a DC motor is very effective, but the braking effect becomes weaker as the armature slows down.

Question 8

____________________ is defined by NEMA as a system of braking, in which the motor connections are reversed so that the motor develops a counter torque that acts as a retarding force.

Question 9

What are the three factors that determine induced voltage?

Question 10

How is plugging accomplished with three phase motors?

Question 11

What is the most accurate method of plug stopping a motor?

Question 12

Dynamic braking circuits for alternating current motors generally include a(n) ______________________________ to lower the voltage to the rectifier.

Question 13

The principle of dynamic braking for a direct current motor is to change the motor into a(n) ____________________.

Question 14

Figure 30-2

In the accompanying figure, the brake is applied automatically when the motor is not operating.

Question 15

When a generator produces electrical power, it produces ____________________, making the armature hard to turn.