For the following reasons, a Power plant capacity rating may be expressed in MW instead of MVA.
In a Generating station, the prime mover (Turbine) generates only and only Active Power. That’s why we rated a power plant capacity in MW instead of MVA. Its mean no matter how large your generator is, but it depends on the capacity of the engine (Prime mover/Turbine) I.e. a 50MW turbine connected to a 90MVA alternator in a power plant will generate only 50MW at full load. In short, a power plant rating is specified in terms of prime mover /Turbine (Turbine rating may be seen by nameplate rating which is in MW or Horsepower (HP) not in MVA) and not by the alternator set coupled to it. Another thing is that, electric power company charges their consumer for kVA while they generate kW (or MW) at the power station (Power plant).They penalize their consumer for low Power factor because they are not responsible for low power factor and kVA but you. Moreover, in power plant, power factor is 1 therefore MW is equal to MVA …… (MW = MVA x P.f). Another interesting & funny answer by one of our Facebook page fan…“Power House means, house of the Power, and we know that the unit or power is Watt. That’s why we rated power plant capacity in MW and not in MVA”. 😉You may also read: From Schematic Drawing to PCB Production, Just Need One Tool
Why Motor rated in kW instead of kVA?
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