Capacitor Bank vs Diesel Generator

Usually DG manufacturer advises clients to keep the capacitors bank switched off to protect the DG sets from getting overloaded. The consideration is purely based on clients lack of knowledge of electrical engineering fundas. Hence mfg may have a valid point for safety of their equipments supplied.

The Dg sets nameplates indicate the KVA, Volt, Hz, Full load current, p.f.= o.8 etc.

These parameters are having particular relationship with each other and any change in one parameter value, other parameters are getting changed.

For example: a DG set say 500 KVA, generation voltage 415V, p.f.=0.8 will have a full load current(I)= 695Amps.

Now the relationships of parameters are as under.

KW = 1.732*Volts(Line)*I(line)*p.f. and KW=KVA*p.f.

So at 0.8 p.f. the set full load amps = 695. The MaxKW=400

Similarly at 0.9 p.f. the full load current= 618.( for same 400KW )

Now if the user is ignorant to understand the engineering principles involved in operating the DG set and if he presumes the set full load amps as given on the nameplate and increses the load on set while improving the p.f., the DG set gets overloaded.

Therefore, by and large the standard advise to users is only to keep the capacitors in switched off mode while operating the DG sets.

I hope this simple explanation will make the matter clear.