i have a generator of 270 kva and load on it is 140 ampere. its load is only a dc motor mainly. 100 to 110 ampere load is depend on dc motor. but when motor running on Pakistani common supply it works properly.

but when we use generator supply motor make a wave of low and high speed which effect on motor efficiency and also on generator sound.
generator sound also changed at that time.

i already change his oil and air filter but no gain.
if some thing you can tell me then please reply me.
i also want to know that how torque load effect on generator supply because my load is not enough for generator capacity, so please reply me in this matter.

dc motor ratting is 200hp.
and i am doing job in printing press thanks

[email protected]

 

Dear sao

The capacity of your generator is less to meet load requirements. Please observe the power factor of your DG set running with DC motor, I think your power factor would be below 0.7 reducing carrying capacity of generator. Maintain it PF at 0.95 by adding power factor capacitors.

Regards
Shaheed
[email protected]

 

rao anwar,

The first question to be asked is: When did this problem start?

The second question to be asked is: Has this generator ever successfully powered this motor in the past, or is this the first times the generator is being used to power the printing press motor?

It would seem that you have some kind of engine-driven generator. I say this because you talked about changing the air and oil filters, so it's some kind of engine powering the generator. Also, it would seem the generator is an AC generator, since you list the rating as KVA.

You say the load is a DC motor. I'm not familiar with how to connect the output of an AC generator directly to a DC motor. There must be some kind of power conversion (AC to DC) between the engine-driven generator and the DC motor. It's not even possible to connect a DC motor directly to the Pakistani grid (which I'm pretty certain is AC). Is it a variable speed drive (a device that converts AC to variable voltage DC using static (electronic) components and circuits in response to some kind of speed or load signal) that converts the AC (from either the Pakistani grid or the engine-driven generator) to DC?

You say if the DC motor (or rather the AC means supplying the DC motor) is connected to the Pakistani grid (nominally operating at 50 Hz) the DC motor output is stable. But when it's powered by the engine-driven generator the generator oscillates. The engine driving the generator has a "governor" that tries to maintain a constant speed so that it produces power at a constant frequency (50 Hz). If there is some problem with the governor keeping the engine speed (and hence the generator speed) constant and stable, then the problem is not the generator or the load. It's the governor.

An electrical generator is a device to convert torque into amperes, and an electric motor is a device for converting amperes into torque.

Disregarding the power factor of the generator (which you didn't provide), 270 "kw" would equal approximately 360 HP, so it would seem the generator is more than capable of powering the DC motor load. Is the motor capable of producing at least the amount of power required by the DC motor, 200 HP I think you said?

You mentioned changing the air and "oil" filters; did you change the lubricating oil filter, or the fuel oil filter?

How old is the engine? Is it in good mechanical condition?

Is the voltage of the generator stable and at rated? The generator, and the engine driving the generator, need to be capable of (rated for) at least the same power as the load. If it the engine and generator are rated for more power than the DC motor draws that should be no problem for the engine and generator--unless the load is so small the fuel can't be properly controlled at such low loads (not usually a problem with equipment you are describing).

So, I hope you can understand some of my problems with the information you have provided. Yes, if an engine air filter is dirty then it can't get sufficient air to run at rated speed. If the fuel filter is dirty, that can restrict the fuel flow to the engine. If the lubricating oil filter is dirty, I don't see how that can cause the power output of the engine to be less than rated.

Please provide more information.