SINGLE PHASE MOTORS WEEK 2

Question 1

What is Duty?

Answer 1

How long the motor can operate

Question 2

What is the service factor?

Answer 2

% of rated work the motor can perform 24 hours/day

Question 3

What is HP?

Answer 3

Rate @ which the motor can work; the output of the motor

Question 4

What is the Speed (rpm) formula?

Answer 4

(120 X frequency)/ Poles

Question 5

Run winding?

Answer 5

Remains connected to the source whenever the motor is running. Uses larger wire and few coils.

Question 6

Stator winding?

Answer 6

The ends of the stator winding can be connected together for various different voltages and speeds. if the voltage source is connected to the winding terminals; a magnetic field is created in the current in the rotor bars, into the rotor, causing the shaft to spin.

Question 7

End Bells/plates

Answer 7

connected to each end of the frame, with through bolts, protrude through holes through the entire frame and connect the end bells together. End plates also house the bearings, the end or centrifugal switch and also protect the inside of the motor depending on the type of enclosure.

Question 8

What is the rotor?

Answer 8

part of the motor that rotates. Consists of a steel core with slots on the outside. Copper or aluminum bars inserted into the slots. These rotor bars are then connected together with two rings @ each end of the rotor, end rings. Squirrel cage rotor.

Question 9

What is in the stator?

Answer 9

Consists of a laminated iron core of silica steel with slots to contain the motor winding. Each of these windings is wound to create a different number of magnetic poles. The # of poles determines the speed of the motor.

Question 10

What does a single phase motor consist of?

Answer 10

Frame, stator, rotor, endbells

Question 11

What motor is not considered a split phase motor?

Answer 11

Shaded pole motor

Question 12

What are the 5 types of single phase motors?

Answer 12

Resistance start induction run
capacitor start induction run
capacitor start capacitor run
permanent split capacitor
shaded pole

Question 13

Motors convert electrical energy into?

Answer 13

mechanical energy & it is rated in HP in North America and KW in other parts

Question 14

What do you need to get the rotor to start? RSIR

Answer 14

Auxiliary contacts or start winding

Question 15

how many turns less does the start winding have than the run winding? RSIR

Answer 15

20-30% less turns

Question 16

Where is the run winding mounted?
RSIR

Answer 16

Closer to the bottom, closest to the stator core

Question 17

The start winding is more ___ and the run winding is more ____/ RSIR

Answer 17

resistive, inductive

Question 18

Once the motor has reached about 75% of its rated speed the ___ will open and remove the ___ from the circuit/ RSIR

Answer 18

the centrifugal switch will open and remove the start winding

Question 19

What is a centrifugal switch? in an RSIR

Answer 19

set of contacts mounted on a spring steel. The amount of centrifugal force will cause these contacts to open.

Question 20

does the run winding stay in the circuit the whole time? RSIR

Answer 20

true

Question 20

What are starting capacitors usually rated for in a CSIR?

Answer 20

50-90 uf

Question 20

Why do split phase motors have bad starting torque? RSIR

Answer 20

due to the phase angle between the current and the voltage.

Question 21

What HP is the CSIR rated for?

Answer 21

1/6 HP to 10 HP

Question 21

What are start capacitors rated in?

Answer 21

voltage and microfarads

Question 22

When the motor has reached 75-80% in a CSCR the ____ opens and removes the ___ and ___ from the circuit?

Answer 22

centrifugal switch will open and remove the start capacitor and start winding

Question 23

Can CSIR be dual voltage?

Answer 23

yes. With the same terminal designations as the resistance or split phase dual voltage motors

Question 24

What are CSCR rated for?

Answer 24

1/2 Hp to 10 HP

Question 25

The CSCR run capacitor is wired?

Answer 25

permanently in series with the start winding

Question 26

The CSCR start capacitor is wired?

Answer 26

in series with the centrifugal switch

Question 27

How are the start cap and centrifugal switch wired in a CSCR?

Answer 27

in parallel with the run capacitor

Question 28

If the run winding, start winding and run capacitor remain in the CSCR circuit; what is removed once the motor reaches 75% of its speed?

Answer 28

Start capacitor

Question 29

What does the run capacitor improve?

Answer 29

power factor

Question 30

What is the most common motor in commercial HVAC?

Answer 30

PSC motor (permanent split capacitor)

Question 31

Does a PSC have a centrifugal switch?

Answer 31

no

Question 32

what is the PSC rated for?

Answer 32

1/20 Hp to 1/2 HP

Question 33

PSC are used typically on?

Answer 33

Direct drive equipment

Question 34

hermetic compressor thermal protection can be ?

Answer 34

externally mounted or internally mounted

Question 35

Hermetic compressor thermal protection is?

Answer 35

built in or mounted in contact with the compressor motor. Senses the unusual temperature rise or excess current draw. Bimetallic strip interrupts current flow.

Question 36

An externally mounted hermetic compressor thermal protection?

Answer 36

senses just temperature and current draw

Question 37

An internally mounted hermetic compressor thermal protection?

Answer 37

above plus loss of charge
not repair or replaceable
cannot be bypassed

Question 38

how many watts does 1 HP have?

Answer 38

745.7 Watts (746Watts)