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Cummins Generators Data
Perkins Generators Data
Volvo Penta Generators Data
Useful Formulae
The power output of an engine may be quoted in bhp (brake horse power) or
kWm (kilowatt mechanical) kWe is the electrical output of the alternator
1bhp is equivalent to 0.746kWm or 1kWm is equivalent to 1.34bhp
kWe is kWm multiplied by the efficiency of the alternator (varies between 0.75 and 0.97)
kVA = kWe divided by power factor (0.8 power factor is generally used for an inductive load)
If the load is totally resistive then the power factor is 1 and thus kVA = kW
The power output of an engine may be quoted in bhp (brake horse power) or
kWm (kilowatt mechanical) kWe is the electrical output of the alternator
1bhp is equivalent to 0.746kWm or 1kWm is equivalent to 1.34bhp
kWe is kWm multiplied by the efficiency of the alternator (varies between 0.75 and 0.97)
kVA = kWe divided by power factor (0.8 power factor is generally used for an inductive load)
If the load is totally resistive then the power factor is 1 and thus kVA = kW
Relationship between the alternator output voltage and the current in amps.
Single phase current = 1000 x kva/voltage. Example 1kva at 230 volts produces 4.35 amps
Three phase current = 1000 x kva/(voltage x 1.732). Example 1kva at 400 volts
produces 1.44 amps per phase
The current can more conveniently be calculated from the following tables
| Single Phase 2 wire |
254 volts
|
240 volts
|
230 volts
|
220 volts
|
127 volts
|
120 volts
|
110 volts
|
| Current per 1 kva |
3.94 amps
|
4.17 amps
|
4.35 amps
|
4.55 amps
|
7.87 amps
|
8.33 amps
|
9.09 amps
|
Example: A 3kva generator operating at 230 volts single phase has an output of 3 x 4.35 = 13.05 amps
|
Three Phase Star Connected
|
440/254 volts
|
415/240 volts
|
400/231 volts
|
380/220 volts
|
220/127 volts
|
208/120 volts
|
190/110 volts
|
|
Current per 1 kva
|
1.31 amps
|
1.39 amps
|
1.44 amps
|
1.52 amps
|
2.62 amps
|
2.78 amps
|
3.04 amps
|
Example: A 50kva generator operating at 400/231 volts 3 phase has an output of 50 x 1.44 = 72 amps per phase
Relationship between the engine speed and the alternator output frequency
| Alternator Pole Pieces |
2 Pole
|
4 Pole
|
6 Pole
|
8 Pole
|
| 50hz frequency |
3000 rpm
|
1500 rpm
|
1000 rpm
|
750 rpm
|
| 60hz frequency |
3600 rpm
|
1800 rpm
|
1200 rpm
|
900 rpm
|
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Generator Self Assembly Kits Mobile Tower Lights Spare Parts
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