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elec theory > SINGLE PHASE MOTORS ILM > Flashcards

SINGLE PHASE MOTORS ILM Flashcards

1
Q

What is a split phase motor?

A

electromechanical device that converts electrical energy into mechanical energy. Functions by splitting the applied power between two parallel windings.

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2
Q

the auxiliary winding is also referred to as?

A

start winding

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3
Q

main winding is also known as?

A

run winding

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3
Q

What is the RSIR motor?

A

separate start and run windings. These windings differ in resistance and inductance.

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3
Q

RSIR phase angle?

A

each winding has a different phase angle, the difference between these two cause the rotor inside the stator to turn

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4
Q

Once the RSIR motor reaches 75% of its rated speed?

A

the centrifugal switch interrupts the current to the start winding

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5
Q

what are the components of a RSIR motor?

A

stator,rotor,start switch,frame

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6
Q

what is the RSIR stator made of?

A

laminated iron plates that are stacked to form a cylinder, constructed with slots to receive the windings, both the start and run windings are mounted here. electrically out of phase by 90 in a two pole.

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7
Q

RSIR start winding is?

A

lighter gauge, greater resistance, fewer turns therefore it has less inductance, lower impedance, higher amp draw

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8
Q

RSIR run winding is?

A

heavier gauge wire, less resistance, greater number of turns, causing greater inductance, higher impedance, lower amp draw

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9
Q

What are the moving parts of the RSIR?

A

rotor and rotor shaft, turns and delivers the mechanical energy. Called torque.

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10
Q

What is the RSIR rotor made of?

A

laminated steel core that is pressed onto the rotor shaft. Mounted inside the motor housing.

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11
Q

End bells?

A

contain the motor bearings, support the rotor and centre the rotor inside the stator

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12
Q

RSIR start switch?

A

interrupts the power to the start winding once the motor has reached 75% of its full run revolutions per min.

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13
Q

Current relay?

A

motor current starting switch, has a coil connected in series with the run winding. NO contacts wired in series with the start winding.

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14
Q

What is a centrifugal switch?

A

motor starting device, mounted on the end of the rotor inside the motor frame. Switch is closed when the rotor is stationary. Switch opens when the motor rotation reaches its 75% of its full rate. Switch disconnects the start winding from the power supply.

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15
Q

What is the initial starting torque of the RSIR?

A

160-175% of the normal running torque

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16
Q

What are the two capacitor start motors?

A

capacitor start induction run motor and capacitor start capacitor run motor.

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17
Q

What is the biggest difference between a RSIR and a CSIR?

A

the CSIR has a start capacitor in series with the start winding of the stator.

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18
Q

What components does a CSIR have?

A

stator, rotor, start switch, frame and start capacitor

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19
Q

What is a start capacitor?

A

electrical storage device, consists of two conductor plates separated by an insulator or dielectric material. Enclosed in a cylindrical bakelite (plastic) container. Only in the circuit for a short time. 3 secs or less.

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20
Q

Why do you want a start capacitor in a CSIR motor?

A

causes the start winding current to lead voltage and the run winding by up to 90 degrees

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21
Q

What is capacitance?

A

ability of a device or system to store electrical energy. rated in microfarads

22
Q

Purpose of a start winding?

A

in every induction motor, provides the phase shift required to initiate motor rotation in a desired rotation.

23
Q

How is a phase shift introduced to a motor?

A

-the start winding may be physically offset from the run winding in the stator
-the start winding may be constructed with more turns of finer gauge wire

24
Q

What is the CSCR motor?

A

similar to the CSIR except it has an additional capacitor that is permanently wired in series with the start winding. This additional one is called the run capacitor.

25
Q

What is the purpose of a run capacitor in a CSCR motor?

A

used to constantly power the start windings with a much smaller phase shift than the start capacitor.

26
Q

What is a run capacitor?

A

constantly energized as long as the motor is running. requires cooling from the oil impregnated dielectric. Supply a small phase shift to the motor, smaller uf rating.

27
Q

How does a CSIR motor operate?

A

the run winding draws 4-5 times its normal current, this starting current creates a strong magnetic field around the coil of the current relay, this lifts the armature of the relay and closes the NO relay. The motor windings become energized and the motor begins to turn when the relay contact points close.

28
Q

What is a PSC motor?

A

single phase motor, has start and run windings. Does not have a centrifugal switch or relay to interrupt the start winding after the motor starts.

29
Q

How are the capacitors wired in a PSC?

A

run capacitor is wired in series with the start winding and in parallel with the run winding.

30
Q

How does a PSC operate?

A

the start winding has greater impedance than the run winding, son before the rotor starts moving, the two windings are out of phase.
once power is applied to the motor, phase difference starts the motor, as the motor reaches near full running rpm the capacitive reactance Xc introduced by the run capacitor and the changing inductive reactance XL in the start winding reach a balance.
the balance of Xc and XL forces the start winding and the run winding in phase with one another. Prevents the PSC motor windings from overheating.

31
Q

What are some applications of the PSC motor?

A

multi or single speed direct drive centrifugal fans, axial fan drives, pumps and circulator drives, refrigeration and air conditioning compressors that do not require high starting torque

32
Q

What motor will replace the PSC?

A

ECM motor

33
Q

What is a CSCR motor?

A

single phase motor with high starting torque and running efficiency, has start and run capacitors. a potential relay.

34
Q

How does a CSCR operate?

A

splitting the phase angle between the start and run winding in the same manner as the PSC motor.

35
Q

What is a potential relay?

A

motor starting device that operates by using counter electromotive force created in the start windings. Only used with CSCR motors. Constructed with a high impedance coil and a set of normally closed contacts.

36
Q

How does a potential relay work with a CSCR?

A

normally closed, contacts closed, powers the motor start windings, as the motor speed increases through the start cycle, so does the cemf value, once the motor reaches 75-80% it opens the potential relay contacts. When they open, it interrupts the flow to the start winding and the motor continues on with only the run winding.

37
Q

What is the point of the CSCR design?

A

give the optimal amount of starting torque and running efficiency. Achieves this by using both the start and run windings when it starts, as well as having a start capacitor and run capacitor in series to the start winding but parallel to each other.

38
Q

Three advantages of the CSCR motor?

A

high starting torque, reduced operating current and smoothness of operation

39
Q

Shaded pole motor is also known as?

A

Squirrel cage motor

40
Q

a shaded pole motor has ___ torque and __ current draw

A

low, low

41
Q

What are the components of a shaded pole motor?

A

frame, stator, single winding, rotor and a shading coil, two to four poles

42
Q

what is the Shading Coil?

A

thick copper ring that is physically wound one turn on a portion of each pole of the stator winding. Purpose is to delay the development
of magnetic flux in that shaded part of the pole so that a rotating magnetic field is created.

43
Q

How does a shaded pole motor operate?

A

pulsating magnetic flux of each pole of the winding. This induces electromotive force in the rotor and causes it to rotate. As the speed increases, the movement of the rotor increases the pulsating magnetic flux becomes more of a rotating magnetic flux. The movement of the rotor always follows from the non shaded part of the pole in the winding.

44
Q

resistive circuit phase angle and relationship

A

0 degrees and it peaks at the same time

45
Q

Hp rating is determined by

A

torque and speed

46
Q

how to calculate HP?

A

(torque X speed)/7121

47
Q

the change the rotation of an RSIR motor?

A

change only the run or start terminals

48
Q

on a CSCR motor the potential relay removes the ?

A

start capacitor
LEAVES the run capacitor, run winding, start winding

49
Q

the PF (power factor) is the ratio comparing?

A

true power in watts and the apparent power in VA ; P/S

50
Q

The SI unit for torque is?

A

newton meters

51
Q

How does a shaded pole motor operate?

A

on the principle of a pulsating magnetic flux, of each pole of the winding. This emf in the rotor causes it to rotate, as the speed increases, the movement of the rotor increases and the rotor turns.

52
Q

The shaded pole motor always follows from the?

A

non-shaded part of the pole to the shaded part of the pole.

53
Q

When the run winding becomes electrically energized the poles of the shaded pole motor?

A

the shaded and non shaded portions of each pole develop opposing magnetic charges when the run winding is electrically energized. This creates an opposing polarity in each individual pole of the motor.

54
Q

Is the shading coil electrically connected to the run winding?

A

NO; it acts to start the motor, develops an induced current from the run winding. This induced current form an opposing polarity in the shading coil as compared to the run winding.

55
Q
A

elec theory (9 decks)

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