can u solve this(alternator excitor rating)

Your numbers don't make sense, unless the order of your column headings don't correspond the the order of the values below (in which case the numbers really don't make sense).

122 volts X 387 amperes = 47214 watts or 47.2 kW, not 7500 kVA or 6000 kW, is only one example.

Are you stating (without stating explicitly) that the field (exciter???) kVA of 7500 or kW of 6000 yields outputs at 122 V, 387 A? If so, that doesn't make sense either.

If you are stating that the generator's output is 7500 kVA with exciter voltage of 122 V at 387 A, then you may have something, but without knowing the generator characteristics, no one can verify whether or not your numbers make sense, much less "can u solve this (alternator excitor rating)."

yeh, the things become crab.

now, let me tell u that the first two figures represent the generator rating in kw and kva,

another two are the excitor's voltage and current values.

now, what kind of characterstics of generator u want to know......

plz tell me how can the rating of excitor calculated ---- take any example

The generator will have a characteristic curve for variations in field (excitor) voltage. Given the data, you can plot that and use a polynomial function to best fit the curve, and I'm not about to begin to explain how that is done.

I can only assume that the figures you have given were either supplied by the generator manufacturer or that you have run tests and measured the results. Which of the two possibilities is the actual case?

It seems that the kVA and kW refer to the gen and the V and I columns refer to th field circuit. However is thesecolumns missing the decimal points! i.e. 12.2volts 3.87Amps?

yeh, the things become crab.

now, let me tell u that the first two figures represent the generator rating in kw and kva,

another two are the excitor's voltage and current values.

there is not any mistake with decimal, the values 122V which we need to feed to dc excitor to get voltage at stator's ends.

plz tell me how can the rating of excitor calculated ---- take any example

Why do men feel the need to ponder things they obviously are ignorant to????

Hi Harjeet.

Your figures MUST be wrong. If in the first instance of the 7.5kVA you need 122V for excitation and 387A you would have 47kVA in the field!

A current of 3.87A would be a sensible figure for field current on this size generator set.

Even if this is the case it would be unusual that the field voltage is as high as 122V. Are you stating the ac voltage into the AVR or regulator circuit? This has no direct bearing on the DC voltage that is fed to the field coils. Many manufacturers use half the output voltage to sense and supply the regulator. this means the same regulator can be used in 110V or 230V systems.

Correlating output versus excitation cannot be done as it depends on the particular manufacturer's specifications. Some things that have a bearing on the excitation are rotor / stator clearance gap, rotor speed, brushed or brushless excitation.

Your question is a little like asking "what is the formula for gas pedal pressure related to vehicle speed". While that is possible to come up with figures for one vehicle they would not be relevant for a different vehicle.