Motor Control

Question 1

The most important reason for interlocking the S contact and the 2M contact in a wye-delta start is too

Answer 1

Prevent a line short

Question 2

A fridge units for a walk in freeze should use LVR or LVP

Answer 2

LVR

Question 3

A dual voltage motor connected to it’s higher voltage will use a __________ current rated OL heaters

Answer 3

Lower

Question 4

In an overload condition the folding contact of a 3 wire will be open yes or no

Answer 4

Yes

Question 5

Is a shading coil is required for a 120v coil really

Answer 5

Yes

Question 6

What is the difference to a schematic and a power CCT diagram

Answer 6

A power CCT is represented as a single line

Question 7

Regarding a NO float switch what defines it’s normal

Answer 7

Not enough liquid to close the circuit

Question 8

Where is the holding contact located in a 3 wire CCT physically

Answer 8

The motor contactor

Question 9

A standard 2 wire does not provide….

Answer 9

Low voltage protection

Question 10

The least accurate timing cycle is the…..

Answer 10

Hydraulic timer

Question 11

What power CCT component normally provides both start and stop functions

Answer 11

Contactor

Question 12

The over current devices in the power CCT of a scim provide

Answer 12

Line to line ground fault protection

Question 13

If a control transformer is used to step down a control circuit where would the best place be to come off of the power CCT

Answer 13

L1-L2 on the line side of motor contactor

Question 14

What type of contact from an overload relay will provide an indicator light when the OL is tripped

Answer 14

NO OL

Question 15

A TD relay can only contain only time delay contacts true or false

Answer 15

False

Question 16

A limit switch is a device that operates by physical contact T/F

Answer 16

True

Question 17

An inductive type proximity sensor detects the presence of almost any material T/F

Answer 17

False

Question 18

The electrical interlocks in a F/R Control circuit will lot prevent a motor from changing directions without coming to a complete stop
T/F

Answer 18

True

Question 19

FLA÷√3 will give the current to be used to determine OL rating for a WYE-Delta T/F

Answer 19

True

Question 20

A WYE-Delta starter needs six conductors between the motor and controller because each scr must be connected individually T/F

Answer 20

False

Question 21

In an overload replay the NC control contact sense excessive conductor temperature T/F

Answer 21

False

Question 22

The jog circuit problem of a mechanical race is easily fixed by a CR T/F

Answer 22

True

Question 23

Plugging is the most effective form of braking and is achieved by reversing any two stator leads T/F

Answer 23

True

Question 24

Why is an induction motor more commonly controlled by an across the line starter

Answer 24

High starting torque low cost and simple construction

Question 25

A switch not meant to start or stop any load is called a?

Answer 25

Isolating switch

Question 26

What hazard is present by using a timer to design a plugg control circuit

Answer 26

A change in load could cause the motor to accidentally be run backwards

Question 27

What braking method requires a reversing controller

Answer 27

Plugging

Question 28

How can the amount of braking torque be adjusted when using dynamic braking

Answer 28

Adjust field strength

Question 29

What are 5 categories of deceleration methods

Answer 29

Friction Plugging DC injection Dynamic Eddy current Regenerative

Question 30

What are four key concepts with respect to electrical controller maintenance

Answer 30

Clean Dry Tighten connections Friction free moving parts

Question 31

What is the main disadvantage of a reduced voltage starter

Answer 31

Insufficient torque

Question 32

What does nema stand for

Answer 32

National electrical manufacturing association

Question 33

Nema controllers are rated in

Answer 33

HP

Question 34

Nema controller ratings are

Answer 34

#00-8

Question 35

How much horsepower is a nema #8

Answer 35

900hp

Question 36

What does IEC stand for

Answer 36

International Electrotechnical commission

Question 37

What is the power rating used for IECs

Answer 37

Watts

Question 38

What system is used for IEC controllers sizing

Answer 38

A-Z

Question 39

A starter that contains a disconnect, oc, contactors and OL in one enclosure is called

Answer 39

A combination starter

Question 40

Motors take up what percentage of the electrical field

Answer 40

46%

Question 41

What is a cabinet that contains multiple motor circuits

Answer 41

Motor control centre or MCC

Question 42

What are required functions of motor control

Answer 42

Safety Starting motor Stopping motor Motor current protection Surge protection Reversing Speed control Jogging Inching

Question 43

A motor control that has physical operation of the start at the location of the actual controller is a

Answer 43

Manuel controller

Question 44

A control circuit with automatic restart and 2 wire control is a

Answer 44

Semi automatic

Question 45

A two wire control circuit provides

Answer 45

Low voltage release

Question 46

A control circuit that has no auto restart is a

Answer 46

Automatic control

Question 47

A 3 wire control circuit provides

Answer 47

Low voltage protection

Question 48

What are the three types of timers

Answer 48

Hydraulic Pneumatic Electrical

Question 49

What time does this describe Accurate Inexpensive Many operating modes

Answer 49

Electric timer

Question 50

What timer does this describe Very accurate with robust build And expensive

Answer 50

Pneumatic timer

Question 51

What stopping method is the most efficient

Answer 51

Plugging

Question 52

Starting a motor in FVS has the benefit of

Answer 52

Higher starting torque

Question 53

What is the benefit of a RVS

Answer 53

Lowered inrush current

Question 54

What are the RVS that are always closed transition

Answer 54

Primary resistive Primary impedance

Question 55

T/F a autotransformer start can only be closed transition

Answer 55

False

Question 56

T/F a wye delta start can be both closed and open transition

Answer 56

True

Question 57

A primary resistive start has a minimum of how many stages

Answer 57

2

Question 58

Starting a motor in a open transition starter can cause

Answer 58

Line disturbances

Question 59

What RVs provides the highest amount of torque per amp of primary current

Answer 59

Auto transformer

Question 60

A wye delta start only works on a motor with ______ and _______ leads

Answer 60

6 and 12

Question 61

The OL device of a wye delta starter is bases of of

Answer 61

Phase current of delta

Question 62

An electronic soft start is a ___________ transition

Answer 62

Closed

Question 63

A soft start only provides what

Answer 63

Voltage control

Question 64

What do pilot devices do

Answer 64

Devices that direct current to its destination

Question 65

Which vfd utilizes a choke and a capacitor in DC link

Answer 65

VVI

Question 66

CSI vfd are ____________ in size

Answer 66

Large

Question 67

CSI are used generally for __________ motors

Answer 67

Large

Question 68

PWM VFD provides the closest ________________

Answer 68

Sinosoidal wave

Question 69

In regards to a VFD what should you consider when running a motor at low speeds

Answer 69

Heat build up in motor

Question 70

Warning on a vfd will / will not result in shutdown

Answer 70

Will not

Question 71

Fault on a VFD will / will not result in shutdown

Answer 71

Will

Question 72

When sizing a VFD it's best to ___________ the VFD

Answer 72

Oversize

Question 73

When using a drive with 1ø it has to be derated by _______

Answer 73

50%

Question 74

What are the main parts of the VFD

Answer 74

Converter DC link Inverter Control processor

Question 75

What parts do the converter contain

Answer 75

Diodes Scr's

Question 76

What does the DC link do

Answer 76

Filtering

Question 77

What does the inverter do

Answer 77

Switching

Question 78

What is the formula for V/HZ

Answer 78

V÷HZ