alternating current machines single phasee
TRANSCRIPT
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SPLIT PHASE CONNECTIONS
RUN WINDING
START WINDING
CENTRIFUGALSWITCH
A C SUPPLY
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• RUN WINDINGS – Heavy gauge wire – High number of turns– Deep in slots
• HIGHLY INDUCTIVE
V SUPPLY
ISTART
IRUN
approx 50 to 55O approx 30O
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SPLIT PHASEFIELD
• Start Windings– positioned close to the surface of the slots– fine gauge wire– fewer turns
• LOW INDUCTANCE
90OE
START WINDINGS
RUN WINDINGS
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START WINDINGS
RUN WINDINGS
RUN WINDING FLUX
START WINDINGFLUX
A BC
D
FLUX
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Starting• The Run Winding of a split phase produces a
pulsating magnetic field.• The Start Winding also produces a pulsating
magnetic field. (30OE ahead of the Run Winding).
• The combined effect is a rotating field, and the motor will start.
• If the start winding is open circuited, the motor will not start (pulsating field).
• The high current could damage the winding.
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Vibration and Motor Mounting• The Run Windings produce a pulsating
magnetic field.• This pulsating field produces pulsating torque
therefore vibration. • Mount all 1 motors on rubber mounts
etc.
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FEATURES• The Run & Start Windings combine to produce a
rotating magnetic field. (not constant strength)• At about 75% full speed the Start windings are
opened. (starting)• The centrifugal switch closes at about 25% full
speed. (stopping)• Washing Machines, Bench Grinders, Industrial
Fans
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POINTS TO NOTE• Relatively poor starting Torque• Limited starts/hour. The Start Winding can
over heat.• Reversal - one winding only. The motor
terminals allow for the reversal of the start winding.
• The centrifugal switch may stick.– Closed - Burnt or damaged Start windings – Open - will not start
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Speed/Torque Split Phase Motor
100
200
300
400
Speed
%
Torq
ue
nsyn
Switch
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CAPACITOR STARTINDUCTION RUNV SUPPLY
I RUN
I START
RUN WINDING
START WINDING
CENTRIFUGALSWITCH
A C SUPPLY
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FEATURES• The capacitor (in series with the start
winding) causes a Start Current Phase Shift. Resulting in an improved rotating magnetic field at starting.
• Good starting Torque. Refrigerators, compressors, Floor Polishers
• Operation (after starting) as the Split Phase Motor
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Speed/TorqueCapacitor Start
100
200
300
400
Speed
%
Torq
ue
nsyn
Switch
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CAPACITOR STARTCAPACITOR RUN
RUN WINDING
START WINDINGCENTRIFUGAL
SWITCH
A C SUPPLY
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FEATURES• Improved Torque
– breakdown– starting
• Rotating field therefore:– improved efficiency– improved power factor– less noise and vibration
• Air Conditioners
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PERMANENT SPLITCAPACITOR MOTOR
RUN WINDING
START WINDING
A C SUPPLY
A
B
C
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FEATURES• Identical windings
– turns– wire gauge
• Low starting torque• Reversal: C is common
– A and C or– B and C
• Easy to reverse and speed control (inductor)• Fans (domestic Ceiling Fans)
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SHADED POLE
TIME0
AB C
A B C
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FEATURES• Low cost and reliable• Low starting torque• Reversal: replace the field the other way
around (if possible)• Use is governed by the cost and reliability.
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Speed/TorqueShaded Pole
100
200
300
400
Speed
%
Torq
ue
nsyn
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UNIVERSAL SERIES MOTOR• As DC series motor.• Laminated Field• Reversal change either the field or the
armature. Swap the brush leads.• Hand held Power Tools, Domestic Appliances
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Speed/LoadUniversal Motor
Spee
d
Load
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2 Speed Motors
N S N SSupply
N S NSSupply
2 PoleHigh &Starting
4 PoleLow
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Testing & Mtce• Remember the resistance of each winding is
very low. (continuity)• Insulation 1MΩ• Ensure the centrifugal switch:
– is clear– free of rust– operates freely– check for wear
• Check mounting rubbers• Capacitor in good order.
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Testing Capacitors • To the capacitor, your meter will operate like a
DC power supply. initially drawing current to charge (low
resistance reading) current decreases as charging continues
(higher reading) capacitor charged (high reading)