Hra 135 Unit 3 Final

Front 1

What are the three main ways that we use motors in the refrigeration field?

Back 1

Large compressors
Water pumps Large fan motors

Front 2

Where does the expense come in when operating a refrigeration cycle?

Back 2

Motors

Front 3

In a motor are we using electrical energy to create mechanical energy or mechanical energy to create electrical energy?

Back 3

electrical energy into mechanical energy

Front 4

What are the two main parts of the motor?

Back 4

Stator and Rotor

Front 5

What is the law about poles attracting or repelling one another?

Back 5

Opposites attract
Likes repel

Front 6

What is created around the stator windings when current passes through them?

Back 6

electromagnet

Front 7

Why do the magnetic poles change in the stator windings?

Back 7

AC current

Front 8

How is voltage applied to the rotor to produce an electromagnet in it?

Back 8

induced

Front 9

What are AC motors called?

Back 9

Induction motors

Front 10

Why doesn’t the current flow through the iron bars on the rotor?

Back 10

Takes path of least resistance

Front 11

In a AC motor what do they call the construction of the rotor?

Back 11

Squirrel Cage

Front 12

What do they call the speed that the magnetic fields change around the stator windings?

Back 12

Synchronous Speed

Front 13

What do we call the difference between the speed of the rotor and the synchronous speed of the motor?

Back 13

Slip

Front 14

When we increase the load on the motor will the slip increase or decrease?

Back 14

Increase

Front 15

Will single phase power create a starting torque in a motor to get it started by itself?

Back 15

NO

Front 16

What are the two ways that starting torque is produced in single phase motors?

Back 16

Start windings, Copper Band on Shaded Pole

Front 17

If the start winding in the motor goes out, can we start the motor without a load by turning it manually?

Back 17

YES

Front 18

To produce a torque to start the rotor, do the run and start windings have to be in phase with one another or out of phase?

Back 18

OUT

Front 19

What are the five types of single phase motors?

Back 19

1. Shaded Pole
2. PSC
3. Split Phase
4. Cap Start / Cap Run
5. Cap Start / Induction Run

Front 20

What is placed around one side of the field to get the rotor turning in a shaded pole motor?

Back 20

Copper Bands

Front 21

Will the rotor rotate towards the copper band or away from the copper band in a shaded pole motor?

Back 21

Towards

Front 22

How big are the shaded pole motors?

Back 22

1/4 HP

Front 23

How much starting torque does the shaded pole motor have?

Back 23

Half of running torque

Front 24

What are the two windings called in the split–phase motor?

Back 24

Start and Run

Front 25

Is there more resistance in the start winding or the run winding?

Back 25

Start

Front 26

Is there more resistance in the start winding or the run winding?

Back 26

Start winding

Front 27

How fast does the rotor have to turn before the start windings are taken out of the circuit and it runs on the run windings only?

Back 27

75% of the rated speed

Front 28

How large are split–phase motors?

Back 28

1/6 to 3/4 HP motors

Front 29

How much starting torque is produced with a start capacitor?

Back 29

3 – 4 x Fulk load torque

Front 30

What does the centrifugal switch do on a motor?

Back 30

Cuts out start windings at 75%

Front 31

Which capacitor will have higher micro farads, the start or the run capacitor?

Back 31

Start capacitor

Front 32

What will increase the running torque and increase the efficiency of a single phase motor?

Back 32

Run capacitor

Front 33

Does a permanent split–capacitor motor have starting components?

Back 33

No

Front 34

In the PSC motor is the run capacitor left in the circuit all the time or is it taken out of the circuit when the rotor reaches speed?

Back 34

All the time

Front 35

What is the horsepower range of a PSC motor?

Back 35

1/6 to 3/4 HP

Front 36

The brown leads coming out of a PSC motor goes to what electrical component?

Back 36

Run capacitor

Front 37

What is the horse power range of a capacitor starter – induction run motor?

Back 37

1/4 to 10 HP

Front 38

What is the horse power range of a capacitor starter – capacitor run motor?

Back 38

½ to 20 HP

Front 39

Typically what type of motor is used in a single phase semi–hermetic compressor?

Back 39

PSC

Front 40

Does the three phase motor have starting components?

Back 40

NO

Front 41

How far apart are the windings in the three phase motor in degrees?

Back 41

120

Front 42

How many hot wires does three phase power have?

Back 42

3

Front 43

Is it cheaper to operate a single phase motor or a three phase motor that is the same horsepower?

Back 43

Three Phase

Front 44

Which type of motor has more starting and running torque, a single phase or three phase motor?

Back 44

Three Phase

Front 45

What are the two winding configurations of the three phase motor?

Back 45

1. Wye
2. Delta

Front 46

Which one of the configurations draws less amperage?

Back 46

Wye

Front 47

Which one of the configurations has a greater torque?

Back 47

Delta

Front 48

How do you change the direction of rotation on a three phase motor?

Back 48

Switch two hot wires

Front 49

What type of switch is used to cut out the start windings in an open type of motor?

Back 49

Centrifugal

Front 50

Why can’t we use a centrifugal switch in a hermetic compressor?

Back 50

Arcing

Front 51

What type of motors are used in the single phase compressor?

Back 51

Split phase, PSC, cap start / cap run

Front 52

How are some hermetic compressor motors cooled?

Back 52

Refrigerant

Front 53

What are the two types of starting relays used on the single phase compressors?

Back 53

Current and potential

Front 54

The coil of the current relay is wired in series with the _________

Back 54

Run windings

Front 55

The switch of the current relay is wired in _______ with the start winding?

Back 55

Series

Front 56

A compressor that doesn’t have start components and is a single phase compressor has what type of motor?

Back 56

PSE

Front 57

What causes the coil on the current relay to close the switch?

Back 57

LRA

Front 58

Is there one size current relay for all size compressors?

Back 58

NO

Front 59

What causes the coil on a potential relay to open the switch?

Back 59

Back EMF

Front 60

Does the potential relay also cut out the run capacitor?

Back 60

No

Front 61

On a potential relay, what hooks to terminals 1, 2 and 5?

Back 61

Start cap, start winding , common

Front 62

What are the seven things to take into consideration when replacing a motor that is not an exact replacement?

Back 62

1. Electrical characteristics
2. Motor construction
3. Insulation type on windings
4. Bearing type
5. Mounting characteristics
6. Shaft size
7. Direction motor rotates

Front 63

What percentage of the rate voltage can we drop or rise and still operate the motor safely?

Back 63

10%

Front 64

If the voltage to the motor is too low, what effect will this have on the amp draw of the motor?

Back 64

It will increase

Front 65

What will the temperature of the motor do when the voltage is too low?

Back 65

OVERHEAT

Front 66

What will the amperage of the motor do when the motor is overloaded?

Back 66

INCREASE

Front 67

f a 0–volt motor pulls amps, how many amps will a 0 volt motor pull at that same horsepower?

Back 67

?

Front 68

Is it cheaper to operate a single phase motor or a three phase motor that is the same horsepower?

Back 68

Three phase

Front 69

What are the two amp ratings of a motor? When will the motor pull LRA?

Back 69

IRA, full load amps

Front 70

How much greater will the LRA be then the FLA?

Back 70

Fivetimes

Front 71

What does a service factor of 1 mean?

Back 71

25% more horsepower

Front 72

What is the frequency of United States power?

Back 72

60 hertz

Front 73

How many hot wires does three phase power have?

Back 73

3

Front 74

If you were installing a motor on a exhaust fan in a bakery where there is a lot of flour in the air, what kind of motor would you install in that application?

Back 74

Closed

Front 75

What are the two common types of bearings?

Back 75

Sleeve and ball

Front 76

What is the advantage of the sleeve bearing?

Back 76

Cheaper, smaller, lighter weight

Front 77

What decreases the friction between a sleeve bearing and the motor shaft?

Back 77

Oil

Front 78

What decreases the friction between a roller bearing and the motor shaft?

Back 78

Grease

Front 79

What does it mean if a motor doesn’t have an oil port?

Back 79

Permanently lubricated

Front 80

If a sleeve bearing motor is mounted in the vertical position, what kind of bearing must it have?

Back 80

Thrust bearing

Front 81

What is the disadvantage of using a ball bearing motor?

Back 81

Noisy, Expensive

Front 82

Which type of bearing is more durable?

Back 82

Ball bearings

Front 83

When you are greasing a ball bearing motor, what must be removed before greasing the motor?rs

Back 83

Relief valve

Front 84

What are the four most popular types of motor mounts?

Back 84

Cradle, belly band , end mount , rigid mount

Front 85

What are the four most common shaft sizes on motors that are less then 1 hp?

Back 85

?

Front 86

In motors that are reversible or can run in either direction, how is this accomplished?

Back 86

?

Front 87

Why do they design couplings on bigger motors to be somewhat flexible?

Back 87

Reduce Vibration

Front 88

What are the three types of drives used to connect with the load?

Back 88

Belt drive, shaft drive and

Front 89

What tool is needed to align big couplings up with the motor and compressor?

Back 89

....

Front 90

What are the two ways that the coupling can be out of alignment?

Back 90

Angular, parallel

Front 91

How can we change the speed on a belt driven piece of equipment?

Back 91

???

Front 92

If we wanted to speed up a compressor with a belt driven motor, would we make the pulley smaller or bigger?

Back 92

Bigger

Front 93

What is the one thing that you have to be careful about when adjusting a pulley to increase the speed of the load?

Back 93

Amp draw

Front 94

What type of oil is used to oil motors?

Back 94

Non detergent 20 weight

Front 95

Is a PSC compressor on an air conditioner bad if no resistance is read between the compressor terminals?

Back 95

Not necessarily

Front 96

What could be installed on an air conditioner that periodically trips out a breaker to solve the problem?

Back 96

Hard Start Kit

Front 97

What is important to remember when replacing belts on a pulley that has two or more belts?

Back 97

Replace all belts

Front 98

What would happen if the belts were too tight?

Back 98

It...