electric generator question

[Carbide_Tipped]

Gen needs to run at 3500rpm to maintain the set voltage. The HP is needed for amps. 700watts=1hp. 7hp x 700=4900watts

[cameron sydenham]

i am not really concerned about the output, what i am looking for is basically can i look at a generator like a generic dyno up to the 3500 rpm. i know that if i turn it at 3500 rpm, i am using the required hp to do that, but can i guage how much power is being used at any rpm lower than 3500?

[khabe]

How much power you need to spin it up to 3600 rpm?
My God!
It depends about load of generator and about losses.
When nothing switched to output of generator then the power you need to spin it is equal to losses like bearings friction and  magnetic games  included drag and even cogging between stator and rotor what highly depends about design - total efficiency of your generator depends about design and used materials, when generator loaded then few more losses will come on like eddy losses, iron losses copper losses ...  Good generators has at least 90% of efficiency. Most of
companies declares even higher - in reallity its mostly like bluff.
When you want to load this generator with 1kW - then also your engine must to be able at least for 1 kW + losses ...+ reserve ...

And ... you have never told us what kind of generator - is it DC or AC ...when dc output then will you need fixed frequency or not ...
cheers,
khabe

[cameron sydenham]

regular store ac generator.

here is where this is pointing.

if i can make my motor turn a this generator at its 3500 rpm, and the generator has load on it, ie accessories plugged into it, and i am using less than 5000 watts to run my motor....... we are in the green.

what i would like to know is if i can turn the generator at any rpm lower than 3500, can i deduce how much hp i am using..??

[khabe]

You did not tell us - frequency important or not - when inductive load then it plays not small role ...
And I dont know is it PM (permanent magnet) generator?
but ok,
when you are able to measure output voltage and current (Amper clamp and Voltmeter ;-) and if you know true efficiency of actual generator - then its simple to calculate the power you using from Engine using for example simple ohm law where P= I x U  ...  you have only add the losses ... I offer 20%

And when you  turn the generator at any rpm lower than 3500 - you also can see wat will happen with voltage and current ... and then to tell us 

Regards,
khabe

Do you use just an electric motor to spin it (Gen)?
Are you trying OU Motor-Generator