appendix

Application Manual – Liquid Cooled Generator Sets
APPENDIX D
Useful
Formulas
TO OBTAIN: SINGLE–PHASE AC POW-
ER
kilowatts (kW) Volts x Amps x PF
1000
kVA Volts x Amps
1000
Amps p ( (kVA unknown) )
Amps p (kW ( unknown) )
Frequency q y (Hertz) ( )
kW x 1000
Volts x PF
kVA x 1000
Volts
# poles x rpm
120
THREE–PHASE AC POW-
ER
VoltsxAmpsxPFx1.732
1000
Volts x Amps x 1.732
1000
kW x 1000
Volts x PF x 1.732
kVA x 1000
Volts x 1.732
# poles x rpm
120
Reactive Power ( (kVAR) )
– –
Volts x Amps x 1 PF2 � Volts x Amps x 1.732 x 1 PF
1000
2 �
1000
% Voltage g regulation g
(f (for steady t d loads, l d from f
No–Load to Full–Load)
–
�
–
VNL VFL � x 100
V FL � x 100 � V NL V FL
% Frequency q y Regulation g
– –
(f (for steady t d loads l d from f
No–Load to Full–Load) �FNL FFL � x 100
Horsepower p required q
tto ddrive i a generator t
kW
0.746 X Generator Efficiency
First cycle y RMS short cir-
cuit it
current (±10%)
D–2 APPENDIX D
Rev. Jan 2011
V FL
F FL � x 100 � F NL F FL
Rated Amperes
pu X��d
F FL
kW
0.746 X Generator Efficiency
Rated Amperes
pu X��d
• “PF” refers to power factor, which is expressed as a decimal fraction. For example,
80% power factor = 0.8 for the purposes of calculations. In general, single–phase
generator sets are rated at 100% power factor and three–phase generator sets at
80% power factor.
• “Volts” refers to line–to–line voltage.
• “Amps” refers to line current in amperes.
• “F” refers to frequency. 0% frequency regulation is defined as isochronous.