Circuit Analysis

0º 90º 180º 270º 360º

CURRENT

VOLTAGE

Pure Resistance Circuit

POWER

E and I are In-PhasePower Factor = 1.0

0º 90º 180º 270º 360º

CURRENT

VOLTAGE

Pure Inductance Circuit

POWER

I Lags E and are Out-of-Phase by 90o

Power Factor = 0.0

0º 90º 180º 270º 360º

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

0º 90º 180º 270º 360º

CURRENTVOLTAGE

Induction: When voltage leads current

Reactance: The resistance encountered during the change of flow

Inductive Reactance

MOTORS

0º 90º 180º 270º 360º

Im

Motor – Main Winding ONLY

E

0º 90º 180º 270º 360º

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

0º 90º 180º 270º 360º

Motor – Main + Start WindingPLUS Start Capacitor

E ImIs

Capacitor Start Motor

0º 90º 180º 270º 360º

Motor with RUN Capacitor ONLY

E and I are CLOSE or In-PhasePower Factor = to or close to 1.0

What type of motor?