# hp to amps

• posted

Is there an easy way to relate engine output to electrical power? I recall it's been discussed here before, but I can't trace the thread.

For instance, what BHP would I need to drive a 6kva alternator at 240Volts?

Regards,

Kim Siddorn

Diplomacy done, plates spun, fires fought, maidens eaten - well, three out of four ain't bad

• posted

that's about 8 electrical hp. 746 electrical watts/hp multiply amps by volts i would suggest a 12 hp engine or more. that would have good regulation and would accept motor starting surges, etc. keep in mind, if you couple direct, you must have the required hp at 1500 rpm. or 3000 rpm, depending on the number of poles in the alternator. the hp on most engines (petrol) drops off as rpm goes down from rated speed. good luck. it's fun sammmm

• posted

Don't forget that hp comes in many different flavours. You should find all the information you need to confuse you here :-

Alan

• posted

KS> Is there an easy way to relate engine output to electrical power? I KS> recall it's been discussed here before, but I can't trace the thread.

KS> For instance, what BHP would I need to drive a 6kva alternator at KS> 240Volts?

KS> Regards,

KS> Kim Siddorn

Rough rule of thumb is 2hp per Kw.

nickh=== Posted with Qusnetsoft NewsReader 2.2.0.8

• posted

Theoretically 1 HP to produce 750 watts but no generator is 100% efficient so work on 1 HP to produce 500 watts and then allow a bit extra. 6kva divided by 500 watts = 12 HP, so allow 15 HP to be sure. Make sure it produces this at generator speed, i.e 1000 rpm for 6 pole, 1500 for 4 pole or 3000 for 2 pole etc. If your engine only runs at 2000 rpm and you have to gear up for a 2 pole alternator to 3000 rpm then you will need 18/20 HP.

Martin.

• posted

Thanks to all who contributed to this thread & I am better hedufercated that I once were ;o))

Regards,

Kim Siddorn

• posted

1 horsepower is equivalent to 746 watts, so to get the horsepower required: 6000 / 746 ~= 8 hp

The alternator won't be 100% efficient though, so you need to add a percentage to the above figures, say 10 Bhp to allow some headroom. If really pessimistic, assume 1 Kva = 2 hp.

Of course, you can fit a smaller engine so long as you limit the load power to within the engine rating...

Regards,

Chris

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