Engineering Formulas
QuantitySymbolUnitSymbolExample
apparent powerSVoltage x CurrentVA120kVA (1000 x V x I )
currentIAmpereA
efficiencyηper unit0.95 (i.e. 95%)
frequencyfHertzHz50 Hz
polespnumber2 pole, 4 pole
pole pairsppnumber4 pole is 2 pp
active powerPWattWkW = 1000 x W
power, inputPinWattW
power, outputPoutWattW
power factorpfper unit0.86
reactive powerQVoltage x Current reactivevar
slipsper unit
speedNrevs per minuteNot SI unit
torqueTNewton . metreNm
voltageVVoltV

QuantityDCAC 1 PhaseAC 3 Phase
Current (I)
Efficiency
Power Factor

Formula

QuantityFormula
Fan load power
Fan load power
Ohm’s Law

(Resistive circuits)

Power (kW)
Power (Hp)
Power Factor
Pump load power (Hp)
Pump load power (kW)
Slip, s,  (p.u.)
Slip,  (%)
Synchronous speed, NS,  (rpm)
Torque (N.m)
Torque (lb.ft)

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