To Find	Direct Current	ALTERNATING CURRENT
		Single-Phase	Two-Phase* Four Wire	Three-Phase
Amperes when Horse-power is known	H.P x 746 E x % EFF	H.P x 746 E x % EFF x P.F	H.P x 746 2 x E x % EFF x P.F	H.P x 746 1.73 x E x %EFF x P.F
Amperes when Kilowatts is known	K.W x 1000 E	K.W x 1000 E x P.F	K.W x 1000 2 x E x P.F	K.W x 1000 1.73 x E x P.F
Amperes when K.V.A is Known		K.V.A x 1000 E	K.V.A x 1000 2 x E	K.V.A x 1000 1.73 x E
Kilowatts	I x E 1000	I x E x P.F 1000	I x E x 2 x P.F 1000	I x E x 1.73 x P.F 1000
K.V.A		I x E 1000	I x E x 2 1000	I x E x 1.73 1000
Horse-power (output)	I x E x % EFF 746	I x E x % EFF x P.F 746	I x E x 2 x % EFF x P.F 746	I x E x 1.73 x % EFF x P.F 746
I = Amperes   ·   E = Volts   ·   % EFF = per cent efficiency   ·   P.F = Power Factor .8   ·   K.W = Kilowatts K.V.A = Kilo-Volt-Amperes   ·   H.P = Horse Power * For three wire, two phase circuits the current in the common conductor is 1.41 times that in either of he other two conductors.

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Ohms Law

SYMBOLS: V = VOLTAGE IN VOLTS I = CURRENT IN AMPERES R = RESISTANCE IN OHMS P = POWER IN WATTS

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Calculating Synchronous Motor Speed

A squirrel cage induction motor is a constant speed device. It cannot operate for any length of time at speeds below those shown on the nameplate at the rated mains frequency without danger of burning out. (VSD and other electronic control excluded).

To calculate the synchronous speed of an induction motor, apply this formula:

Srpm = 120 X F
                 P

Where:

Srpm = Synchronous revolutions per minute
120   = constant
F       = supply frequency in hz (cycles / second)
P       = number of motor winding poles

Example: What is the synchronous speed of a 4 pole motor at 50hz?

Srpm = 120 X F
                 P

Srpm = 120 X 50
                 4

Srpm = 6000
              4

Srpm = 1500