Motor Control 3: Lesson 1 - DC Motor Control

Question 1

The ______ motor can be started manually with a rheostat.
Select one:

a. AC
b. DC

Question 2

Most new or upgraded DC systems use what type of starting method?

a. contactor
b. electronic DC drive
c. rheostat

Question 3

When starting a DC motor with a rheostat, the current at the field winding is ______ and the current at the armature is ______.

a. high / high
b. high / low
c. low / high

Question 4

During the operation of a DC rheostat motor starter, the resistance is ______ in the field winding and ______ in the armature until the motor is brought up to full speed.

a. increased / increased
b. increased / reduced
c. reduced / increased

Question 5

Most DC motor contactors consist of ______ set(s) of contacts.

a. one
b. two
c. three

Question 6

The standard coil voltage ratings for DC contactors are 12, 24, 48, 120, and ______.

a. 240 V DC
b. 277 V DC
c. 480 V DC

Question 7

DC currents stay ______ the zero axis and maintain a constant current flow to the motor.

a. above
b. at
c. below

Question 8

It is important to make and break contacts as quickly as possible to extinguish the arc promptly and to extend the life of the contacts and contactor.

True or False

Question 9

Arc chutes typically absorb ______ than 80% of the energy released during the interruption of current flow as the contacts open.

a. greater
b. less

Question 10

The magnetic ______ coil produces a magnetic field between the breaking contacts that forces the arc up, increasing the length of the arc and causing it to dissipate faster.

a. blowout
b. contactor
c. overload

Question 11

Because solid-state drives do not use ______, energy is not wasted in the form of heat.

a. coils
b. overloads
c. resistors

Question 12

Which section of solid-state DC drives is capable of varying the motor speed above and below the motor base speed?

a. Control section
b. Power section

Question 13

Which section of solid-state DC drives supplies the DC voltage to the motor?

a. Control section
b. Power section

Question 14

How many DC motor wiring configurations are there?

a. 1
b. 2
c. 3

Question 15

Control of the armature or field voltage is used to control the speed.

True or False

Question 16

Tachometer and encoder are two devices that are used to monitor the ______ of the motor.

a. current
b. speed
c. torque

Question 17

The ______ section of a DC drive is also capable of controlling the motor direction.

a. control
b. power

Question 18

DC drives use a ______ method to smoothly accelerate and decelerate the motor.

a. reduced voltage
b. ramping
c. soft start

Question 19

Ramping works well for ______ loads.

a. large
b. small

Question 20

When stopping heavy loads without a brake, the large inertia of the load continues to rotate the motor after the ramp down voltage has stopped.

True or False

Question 21

Dynamic braking is a motor braking technique where the motor is operated as a ______ after the main power is removed.

a. capacitor
b. DC generator
c. mechanical brake

Question 22

The braking resistor is connected to the ______ during dynamic breaking.

a. armature leads
b. field winding leads

Question 23

Which braking method decelerates the motor faster than the other?

a. Dynamic braking
b. Regenerative braking

Question 24

Regenerative braking returns the regenerated power of a DC motor back to the ______.

a. capacitor
b. DC generator
c. power source

Question 25

When performing maintenance with the motor off, a visual inspection should include a check for excess dirt accumulation, burns, or damaged starter components.

True or False

Question 26

To check if a rheostat is working properly, test each tap for a different resistor value using a DMM.

True or False

Question 27

Most DC motor drives detect and display common circuit and/or fault numbers to help identify problem conditions.

True or False