How to choose power rating

How to choose power rating

It is confusing to select a proper genset. We try our best to help you to decide which power output you really need. Too low output will result in insufficiency of necessary power, genset overload, and short service life. Too high output will lead to the high investment, low loading rate, high fuel consumption, and short service life. 

• Worksheet for apparent power (kVA) 

Voltage 220/380V, Frequency 50 Hz 

- Nominal Current (6) = power (2) x 1000/ cos φ(3) x 3 x 220 
- Starting current(8) = nominal current (6) x starting power (4) 

According to above table: 
- Max. total nominal current: 270A 
- Max. total starting current: 351A 
- Therefore, apparent power for max. current is: 351 x 3 x 220 / 1000 = 231kVA 

*** Remark: 
- Sequence of high kW motor starts is important in selecting apparent power kVA 
- High loads before low loads will be better for gensets. 

• Worksheet for active power kW 

From above calculation: 
- Total Active power, : 125 kW 
- 24-hour average output: 82 kW 
- Max. required active power: 82/0.6 = 136 kW (or the value of total active power which ever is smaller). 

• Select genset rating 

From about calculation, you should choose genset output 230 kVA/ 185 kW. 

If you intend your genset to run as standby power source in case of mains failure, the running time is not over 1 hour in 12 hours, it is recommended to define above required power as Limited Time Power – LTP. 

If you intend your genset to run as commercial prime power source in stead of mains grid, the running time is over 1 hour in 12 hours, it is recommended to define above power as Prime Power - PRP. 

If you intend your genset to source a constant load, it is recommended to define the above power as Continuous Base Power. 

Normally, continuous base load output is not declared in the commercial genset catalogue. Contact us for further instructions. 

• Other notices: 

- The sequence of electrical motor starting will effect your genset power sizing.. 
- Nonlinear loads: US, SCR, frequency inverter, electronic ballast, electronic power module effect much to generating quality of genset. Therefore, if nonlinear load is considerable, genset output should be increased, and permanent magnetic generator and 3-phase sensing AVR should be used. 
- Some types of load can create reversed output such as: cranes, lifts, hoists. In this case, ensure reversed power must be less than genset output to avoid overspeed.