Circuit Analysis
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CURRENT
VOLTAGE
Pure Resistance Circuit
POWER
E and I are In-PhasePower Factor = 1.0
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CURRENT
VOLTAGE
Pure Inductance Circuit
POWER
I Lags E and are Out-of-Phase by 90o
Power Factor = 0.0
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CURRENT
VOLTAGE
Pure Capacitance Circuit
POWER
I Leads E and are Out-of-Phase by 90o
Power Factor = 0.0
Inductance & Reactance• Inductance:– The out-of-phase condition between voltage and
amperage
• Reactance:– The resistance voltage encounters when it changes
flow
• Inductive reactance:– A combination of inductance and reactance– Necessary for the starting and running of an
induction motor
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CURRENTVOLTAGE
Induction: When voltage leads current
Reactance: The resistance encountered during the change of flow
Inductive Reactance
MOTORS
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Im
Motor – Main Winding ONLY
E
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Motor – Main + Start Winding
E Im Is
Split Phase Motor
Capacitive Reactance• Capacitors can create an out-of-phase condition
between voltage and amperage– The voltage lags behind the amperage
• Capacitors increase motor starting torque
© 2005 Refrigeration Training Services - E1#2 AC and DC Current v1.2 10
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Motor – Main + Start WindingPLUS Start Capacitor
E ImIs
Capacitor Start Motor
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Motor with RUN Capacitor ONLY
E and I are CLOSE or In-PhasePower Factor = to or close to 1.0
What type of motor?