Chapter 5

Question 1

What is the difference between a manual motor starter and a magnetic motor starter?

Answer 1

Manual has a manually operated switch and has overload protection.
A magnetic has an electrically operated switch, includes overload protection.

Question 2

What is the function of a soft starter?

Answer 2

Motor control device that provides gradual voltage increase and decrease.

Question 3

How do electric motor drives differ from motor starters?

Answer 3

EMD’s perform the same functions as motor starters, but also vary motor speed, reverse motors, provide additional protection features, and display operating info.

Question 4

What are the traditional methods used to provide reduced-voltage starting?

Answer 4

Primary resistor starting

Question 5

What can be used as a solid-state switch?

Answer 5

A solid state starter is a motor starting device that uses solid state switches to control voltage to a motor.

Question 6

How are voltage and frequency related when controlling speed in an AC motor?

Answer 6

Voltage and frequency must be increased and decreased in equal amounts.

Question 7

What is the primary function of a switch?

Answer 7

Start, stop, or redirect flow of current.

Question 8

When are two-wire motor control circuits used?

Answer 8

When motors are required to operate automatically from such control devices as liquid level switches, pressure switches, or temperature switches.

Question 9

T/F - Direct hard wiring is the most straightforward and oldest motor control method.

Answer 9

True

Question 10

T/F - A locked rotor is the condition in which a motor is loaded so heavily that the motor shaft cannot turn.

Answer 10

True

Question 11

T/F - Magnetic motor starters include high-power contacts for switching a motor ON and OFF and typically include auxiliary contacts that are used in the control circuit.

Answer 11

True

Question 12

T/F - The voltage of a control circuit is higher than the rating of the motor in most motor control circuits.

Answer 12

False

Question 13

T/F - DC drives control speed by varying the amount of voltage and current on the field and armature of the motor.

Answer 13

True

Question 14

T/F - Reduced-voltage starting of large horsepower motors typically causes problems in power distributions systems.

Answer 14

False

Question 15

T/F - Autotransformer starting is a motor starting method that uses a tapped 3 phase autotransformer to provide reduced-voltage starting.

Answer 15

True

Question 16

T/F - Typically, triacs are used as solid-state DC switches.

Answer 16

False

Question 17

T/F - Fans and pumps are typically classified as variable torque/variable horsepower loads.

Answer 17

True

Question 18

T/F - Electric motor drives are programmed to apply a voltage boost at low motor speed to compensate for the power loss of a motor.

Answer 18

True

Question 19

T/F - Placing contactors and soft starters in parallel allows for soft starting and soft stopping of motors without the need for large heat sinks during motor operation.

Answer 19

True

Question 20

T/F - Some electric motor drives allow control functions to be controlled through standard communication ports such as RS-202C ports.

Answer 20

False

Question 21

T/F - Wye-delta motors are specially wound with nine leads extending from the motor to enable the windings to be connected in either a wye or delta configuration.

Answer 21

False

Question 22

T/F - Typically, the control voltage used by electric motor drives is a low voltage, 24VDC.

Answer 22

True

Question 23

T/F - Analog input devices/signals connected to electric motor drives include potentiometers and variable voltage inputs.

Answer 23

True

Question 24

_____ are also known as holding or sealing circuits.

Answer 24

Memory

Question 25

Transistors, silicon-controlled rectifiers, triacs, and alternistors are used as _____ switches.

Answer 25

solid-state

Question 26

A(n) _____ _____ circuit is a circuit that provides control functions such as starting, stopping, jogging, direction of rotation control, speed control, and motor protection.

Answer 26

motor control

Question 27

A(n) _____ is a starter that has an electrically operated switch (contactor) and that includes motor overload protection.

Answer 27

magnetic

Question 28

Soft starting is achieved by _____ a motor's voltage gradually in accordance with the setting of the ramp-up control.

Answer 28

increasing

Question 29

Electric motor drives are either AC drives or DC drives, with _____ drives being the most common.

Answer 29

AC

Question 30

When using the _____ method, motor speed is controlled from the keypad of the electric motor drive.

Answer 30

Local

Question 31

_____ _____ starting is a motor starting method that uses resistors connected in the motor conductors to produce a voltage drop.

Answer 31

Primary resistor

Question 31

_____ _____ starting is used to reduce the large current drawn from the power company when full-voltage starting is applied to large horsepower motors.

Answer 31

Reduced voltage

Question 32

The _____ applied to the stator of an AC motor must be decreased by the same amount as the frequency when controlling speed.

Answer 32

voltage