Generator Feasability

Let's make a simple approximation:

Power required to move generator = Power consumption / generator efficiency

Power = Torque x angular speed

In SI, power is in W, torque is Nm, angular speed is rad/s.

That's all you need. The rest is information you'll have to obtain from the generator manufacturer, or tests.

Also, for efficiency in bhrescobar's formula you could insert 90% and not be too far off -- if you are only looking into feasibility for a small generator. If a few percent one way or another equates to a large amount of money, then you'd need details on the particular generator, prime mover. etc.

As a general rule I have used 1.5 horse power to 1 kw

I run a 100 kw generator and safely power 150 hp of motors

although it must be considered starting takes significant power draw

I step start a 125 hp motor not under significant load

these are rules of thumb use them if they help discard them
if your not sure .

Does this surprise you?

The power calculation of a generator set is done with an expected life and an expected power percentage average. For short periods, it will and can give more power. A generator set for continuous power is way bigger than the same power for emergency use.

A motor power (can also be done in kW) is the absolute max power that it can give continuously in a certain environmental temperature, pressure and humidity situation. This is a figure that also gives a good idea of what you can do with the motor but it can't be taken as the startup power, it is this startup effect (getting your machinery from 0 RPM to the work speed) that is determining to power of your motor. Each motor has a 0 RPM torque, which needs to be greater than the torque needed to get your machine working. It is seldom that your motor is running at the power as denoted on the type plate.

It is not because you have a 100 kW motor that it will speed up till your machine consumes 100kW. (it is like the problem when you replace a 60 W bulb with a 20W , you will only get less light and your 20 W bulb will not explode)

Thanx for the reply Ken.I've been reading your blocks this AM.Great stuff.

You're welcome. I try to insert at least a few reasonable posts in among my rants!