Powerpoint - Electric Motors/Capacitors Flashcards
In Hvac, electric motors are used to turn fans, _____ and ________
fans, pumps, and compressors
Name 5 parts of an electric motor;
- stator with windings
- rotor
- bearings (ball or sleeve)
- end bells
- housing
Ball bearings are lubricated by ______
grease
Sleeve bearings are lubricated by ____
oil
Electric motors frames are vented or totally _______
enclosed
Electricity and _______ are used to create a motors rotation
magnetism
Unlike poles of magnets _______
Like poles of magnets _______
attract
repel
The stator has insulated wire windings called ______ and _______ (auxiliary windings)
starting and running
The start winding enables the motor to start, it ensures the rotor starts and turns in the proper direction. They are wound with a ______ wire, it is _______ from the cct after is starts
smaller, removed
Start windings are closer to the ______ of the motor and run windings are closer to the _______
inside, outside
Start capacitors are used to increase starting torque 300- _____%
500%
Start capacitors have high capacitance at 75-____MFD
75-600MFD
Start capacitors are _________ duty only and never apply voltage exceeding ____% of rating
intermittent duty and 130%
Start capacitors voltage rating replacements should never be lower than oem and replacement capacitor must have a capacitance of within ___%
20%
Run capacitors are used to improve power factor and reduce current, lower capacitance at 2-___ MFD
2-60MFD
Run capacitors are ________ duty and voltage should not exceed ____% of rating, capacitance should be within 5%
continuous duty, 110%
CSCR - Capacitor start capacitor run motor:
Start and run capacitor are wired in ________, run capacitor stays in circuit as long as motor is running
parallel
Motor slip is the difference between a motors _________ speed and actual running speed, the difference in speed is caused by the _____
synchronous, load
Motors should operate within ___% of its rated voltage
10%
low voltage will cause the motor to draw high ______ and cause the motor to overheat
current
high voltage can cause hot spots within the motor, may cause a decrease in motor _____
current
Full load amperage (FLA) is also called rated load amperage (RLA), and it is the current draw while operating at full load conditions and rated ______
voltage
The RLA or FLA is approximately 1/5 to ____ of the locked rotor amperage (LRA)
1/5 to 1/6
Locked rotor amperage is approx 5-__ times higher than the RLA
5-6 times
Service factor is defined as reserve ___
hp
Service factor is the range a motor can safely operate past its 100% level for short period of ____
time
Frequency is the number of _____ per second
cycles
Canada and US operate at a frequency of ___ hz
60
Most other countries operate at frequency’s of ___hz
50
Split phase motors have two separate motor ______ and a medium amount of starting torque.
RPM ranges from 1800-_____
windings
1800-3600RPM
Centrifugal switches are used commonly on open motors to disconnect the ______ winding
start
The centrifugal switch disconnects the start winding when the motor reaches 75% of its _____
speed
Capacitor start motor has a _____ starting torque, start cap is wired in ______ with the start winding and is removed from the cct after _____
higher, series, start
CSCR is the most efficient _____- phase motor used
single phase
CSCR are normally used with belt driven _____
fans
Potential relays are used on motors requiring ____ starting torque
high
Potential relays have two components; name them
coil and contacts
potential relay coils have ____ resistance (10,000 to 40,000ohms)
and are wired between terminals __ and __
contacts are between __ and __
high, coils 2 and 5
contact between 1 and 2
Potential relays contacts are normally _____ and are connected between terminals __ and ___
closes, 1 and 2
CSIR - Capacitor start Induction Run:
Line power applied and causes rotor to turn creating ______ enough to hit pick-up voltage and drop out potential relay circit
BEMF
Potential relays operated on induced voltage across the _____ winding and relay is normally _____
start winding
closed
In a potential relay, the normally closes contact opens when the BEFM rises to specific line voltage, then the start capacitor is _______ and now motor operates as a PSC motor
removed
Current relays are used on _____ compressors
small
Current relays are used on single phase, _______ hp motors
fractional
RSIR- Resistance start Induction run:
high LRA current in current relay coil closes the current relay contact and powers the _____ winding
start winding
Electronic Relay is used to disconnect the _____ winding, it is a solid state motor starting _____, normally PTC (positive temp coefficient), that means when temp goes up so does _______
start, device, resistance
PSC motor is the simplest ____-phase motor
split phase
PSC run capacitor is connected across the start and run terminals and the starting torque is ___
low
PSC motors can be single speed or multi speed and can be adjusted by swapping motor _____
leads
Shaded pole motor:
___ starting torque, not as efficient as ____ motor, small shaded pole (starting windings) at corner of each ____, manufactured in the fractional hp range, provides induced current by creating phase shift in ______ field
low, PSC, pole, magnetic field
Single-Phase Hermetic Motors:
have start and run windings, uses ____ to remove start windings from cct, does not use centrifugal ____, will have run cap to improve _______, designed to operate in ________ atmosphere, common terminal is connected to both the start and run _______
relays, switch, efficiency, windings
Two speed compressor motors:
speed operation by wiring compressor motor to operate as a 2pole motor or __pole motor, are used to control ______ required by small compressor, considered as two motors in one ______, one turns at 1800 and the other at 3600RPM, have more than 3 motor terminals
2 or 4 pole, capacity, housing, 1800 and 3600rpm
Special Application Motors:
some single speed motors have more than __ motor terminals, some manufactures design an auxiliary winding in the compressor to give the motor more _______
3, efficiency
Variable speed motors:
Controlling motor speed gives better ________, decreasing motor speed during low conditions increases ________, voltage and frequency of power supply determines motor _____
efficiency, efficiency, speed
Cooling Electric Motors:
All motors must be cooled due to heat from electrical _____, hermetic motors are cooled with ________ mainly, open motors are cooled by the _____, some very large motors are cooled by ______
energy, refrigerant, air , water
Capacitor start induction run motor becomes which type of motor after the start capacitor drops out of the circuit?
Split phase/PSC
Start capacitor is removed from the circuit when the _____ rises to a the _______ voltage
BEMF
pick-up
CSIR operates as ____ motor once the start capacitor drops out of the circuit which occurs after BEMF rises to pickup voltage
PSC
When the CSIR motor is off, the open potential relay contacts close so it can be used in the circuit again on start-up. True or False?
True
In a potential relay, ine power across start winding creates ______ which will meet pick-up voltage specs and ___ contacts will open and drop out start capacitor/start circuit
Back EMF
N.C
What is the purpose of run capacitor?
increase efficiency
Purpose of a start capacitor?
Provide starting torque
Current relay is based on ________ and the contacts are normally ______
current
open
Total voltage in parallel for a capacitive circuit will be equal to the _______ of all capacitors.
lowest
