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Flashcards in DC Motors Deck (26):
1

Which of the following is the best description of the DC motor

A machine that converts electrical to mechanical energy

2

What two factors determine the torque developed by a DC motor

Field and Armature flux

3

With a rheostat connected to the Armature blank resistance is used at the base speed

Minimum

4

To adjust the speed of the shunt motor above the base speed we control current in the ...

Shunt field

5

If you notice arcing at the brushes of a DC shunt motor you could adjust the brushes blank the motors direction of rotation to reduce the arcing

Against

6

What is the best way to reverse the direction of a DC motor

Reverse the Armature connections

7

When a DC motor is producing torque which of the following is a constant

Number of Armature conductors

8

The direction of rotation of a series motor could be reversed by inner changing the leads from the supply battery

False

9

Using the motor speed characteristic curve chart select the letter of the curved up longs to each motor connection compound motor ,series motor, shunt motor

Series is the lowest, compound motor is the middle, shunt is the top

10

What is the effect on the torque of a DC Shunt motor in the field current is kept constant an Armature current is halved?

Torque is halved

11

Which of the following symptoms would suggest improper operation of a DC motor?

High operating temperature, sparking at the brushes, excessive vibration, all the above

12

Which of the following is a typical fault with the DC motor?

Shorted windings infield or Armature, open winding infield or Armature, grounded winding infield or Armature all the above

13

Which of the following test equipment is most effective in conducting insulation test?

Megger

14

A shorted coil can be discovered with which of the following maintenance procedures?

Growler check

15

Which of the following will result in excess of arcing at the brushes?

Broken brush tension spring, incorrect interpole polarity, I communicator Mica, all of the above

16

Series windings consist of blank turns of blank wires

Few turns large wires

17

Shunt windings consist of blank turns of blank wires

Many turns small wires

18

The DC Shunt motor shown below will rotate blank

Clockwise

19

The CEMF generated by a DC motor is proportional to what two variables?

Flux and speed

20

The Armature current of a DC motor operating at the speed is limited by what two variables?

CEMF and Armature resistance

21

What is the best feature of a shunt motor?

Constant speed

22

What is dangerous to do to a shunt motor?

Open shunt unsafe speed

23

What is the best feature of the series motor?

High torque starting

24

What is dangerous to do to a series motor?

Must be coupled directly not with a belt or chain

25

What is the danger of misconnecting accumulative compound DC motor as a differential compound DC motor?

Motor will reverse

26

What are the two functions of the holding coil?

Lots of field, Holds contact in place