Replacing an Electric Motor - What of hp?

I think your problem lies in that an electric motor produces instant torque even at low RPM. A ICE will not produce torque until it reaches it's design RPM.

Ken

Yes you can see my reservations although it's still unclear to me if an electric hp and an internal combustion engine compare 1 to 1 even under simular load conditions It may be practical to just use a larger hp gas motor to be sure to cover the power curve ?

You could probably start a 500 hp motor with your generator (or bigger even) if there wasn't a full load on it. HP ratings relate to full load.

Replacing a motor motor with an engine (ooohh, picky word use there!) depends on the task at hand and where the energy comes from.

I suggest Diesel Generator hand book By LL Mahon for referance it would give you a very good idea on your question murali

$300 at Amazon I'll check the library

generator kVA = motor hp x X where - X = 4 for direct to line starters, 1.4 for star-delta starters, 1.6 to 2.8 for auto-transformer starters depending on No of taps, 0.8 for slip-ring motors with resistance starters rising to 1.5 for motors with high starting power factor. If you can read .dwg or .dgn or .dxf drawings I can send you a more detailed breakdown.

Iv'e used the 1.5 ratio for my sawmill applications where loads are variable ie. fluid temps .to cover it our assumtion was 100 kw could start a lightly loaded 125 hp but to be safe I step started it .

i like to ask this type of ? 1)what is torque in the double cyilnder IC engine.

Since you need the motor to drive a specific load, you can change the electric motor with any other type with the same output data. For starting the 75HP motor, if the load is not connected to the motor during starting then you have a problem with the generator. Otherwise, you need to know the transient characteristics of the load & motor during starting. You can refer to any literature in electric drive. If you need more help contact me at email khatib_ab@yahoo.com

My application is a sawmill and loads are variable as hydrolic pumps may have cold fluids etc. The blade is of course not under load . My question was really on a seperate piece a wood splitter that currently is powered by a 50 hp electric for hydrolics .I thought electric motors actually worked harder and for that application I might need a 75 or 100 gas or diesel..You can see my reasoning

The only consideration in my view is:
If ypu bought a motor-generator Set, then it has Auto-Throttle control to regulate out-put Volage on varying load. Then how you plan for it?