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Circuit Analysis
Pure Resistance Circuit
0º
90º
180º
270º
360º
VOLTAGE
CURRENT
POWER
E and I are In-Phase
Power Factor = 1.0
Pure Inductance Circuit
0º
90º
180º
270º
360º
VOLTAGE
CURRENT
POWER
I Lags E and are Out-of-Phase by
Power Factor = 0.0
o
90
Pure Capacitance Circuit
0º
90º
180º
270º
360º
VOLTAGE
CURRENT
POWER
I Leads E and are Out-of-Phase by
Power Factor = 0.0
o
90
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
Inductive Reactance
Induction:
When voltage leads current
0º
90º
180º
VOLTAGE
CURRENT
Reactance:
The resistance encountered
during the change of flow
270º
360º
MOTORS
Motor – Main Winding ONLY
0º
E
90º
Im
180º
270º
360º
Motor – Main + Start Winding
0º
90º
180º
270º
360º
E I I
m s
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
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Motor – Main + Start Winding
PLUS Start Capacitor
0º
Is
90º
180º
270º
360º
E Im
Capacitor Start Motor
Motor with RUN Capacitor ONLY
0º
90º
180º
270º
360º
E and I are CLOSE or In-Phase
Power Factor = to or close to 1.0
What type of motor?