Unit 2 Motors 1

Front 1

CEMF is determined by.

Back 1

1: The number of turns of wire in the armature.

2: The strength of the magnetic field of the pole pieces.

3: The speed of the cutting action.

Front 2

Difference between DC motors and Generators

Back 2

Generators take mechanical energy and convert it into electrical energy

Front 3

Torque is determined by

Back 3

1: The strength of the magnetic field of the pole pieces. 2: The strength of the magnetic field of the armature.

Front 4

The comutator is the same in a DC motor and generator. True or False

Back 4

True

Front 5

How does a comutator work differently in a DC Motor.

Back 5

It works as a rotary switch in a motor where it works as a rectifier for the generator.

Front 6

When unloaded, the armature speed will continue to increase until?

Back 6

CEMF is roughly equal to the applied EMF.

Front 7

As load is added to the motor: -Exisiting torque is insufficient\sufficient to maintain speed. -Armature rotation increases\slows due to insufficient torque. -CEMF increases\decreases due to slowed speed of rotation. -Current flow in armature increases\decreases due to decreased CEMF. -Magnetic field strength increases\decreases with increase in current flow. -Torque increases\decreases due to increase in field strength.

Back 7

Insufficient, slows, decreases, increases, increases, increases

Front 8

DC Shunt Motors are constructed by connecting the armature winding in _________ with a shunt field winding.

Back 8

Parallel

Front 9

Windings made of smaller gauge wire with more turns.

Back 9

Shunt

Front 10

Windings with large wire and fewer turns.

Back 10

Series

Front 11

Shunt motors feature excellent speed characteristics, and are generally referred to as

Back 11

Constant speed motors

Front 12

Full-load speed is generally within ___% of the no-load speed.

Back 12

10%

Front 13

The regulation of speed by a DC shunt motor is primarily dependent on the

Back 13

resistance of the armature

Front 14

Assuming the excitation current produced by the shunt field is held constant, armature current determines.

Back 14

torque

Front 15

Current flow through the armature is determined by the

Back 15

resistance of the armature, and the CEMF that is induced into the winding.

Front 16

CEMF Equation

Back 16

E (cemf) = I (load) x R (armiture)

Front 17

The operation of a DC Series motor is significantly different from the Shunt motor, and results in excellent _______ characteristics

Back 17

Torque

Front 18

Because the series field is connected in series with the armature winding, the current that flows through the armature is equal in magnitude to the current in the

Back 18

series field.

Front 19

As load is added to the DC series motor: -Torque is insufficient\sufficient to meet new load demand. -Motor rotation increases\slows due to torque. -CEMF increases\decreases due to armature rotation. -Current increases\decreases due to CEMF. -Torque increases\decreases due to current flow.

Back 19

Insufficient, slows, decreases, increases, increases.

Front 20

If motor current increases 2X, torque will increase _X.

If current increases by 3x torque increases by _x

Back 20

4x, 9x

Front 21

Series motors are capable of generating very high starting torque, averaging ___% of the rated full-load torque.

Back 21

450%

Front 22

DC Series motor should always be __________ to the load being driven.

Back 22

directly coupled

Front 23

A motor with differential compounding starts with its rotation being determined by the polarity of the shunt winding. As load increases, the series field strength will increase. If enough load is added, the series field, which is connected in the opposite polarity, will

Back 23

take over, causing a sudden and violent change in rotation.

Front 24

When connecting a DC Compound motor, the following procedure should be followed to prevent a differential connection.

Back 24

1: Disconnect the motor from the load.2: Connect the armature and series windings to form a series motor.

3: Briefly apply power to determine the direction of rotation. If the motor turns in the opposite direction as desired, reverse the polarity of the connections.

4: Connect the shunt winding of the motor, apply power, and observe rotation.

Front 25

Field loss relay is designed to prevent the motor from becoming a series motor in the event that the

Back 25

Stunt winding is lost.

Front 26

The coil of the relay is connected in _______ with the shunt winding. As long as current is flowing through the winding, the relay’s NO contact in the control circuit will remain closed.

Back 26

Series

Front 27

Reverse motor direction by switching witch 2 leads

Back 27

Armature a1 and a2