# i have 10 kva electric generator what kind of torque needed to start?

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Genarators are rated in KVA at a particular power factor, which is 0.8 for most manufacturers.

This rating indicates you must have a driver capable of supplying the KW and not the KVA.

The KW of a normally rated 10 KVA generator is KW = KVA * PF = 10 * 0.8 = 8 KW.

The theoretical HP is 746 watts. Disregarding the efficiency of the generator and driver, the HP required for 10 KW will be 10000 / 746 = 13.4 HP.

I would use a combined efficiency, for both the driver and generator, of 80%. This will make the required HP be 13.4 / 0.8 = 16.75 HP.

The nearest standard HP in that range will be 20 HP, unless you can find one which is greater than 16.75 HP, but less than 20 HP.

Generally you don't start a generator with a heavy load switched on. The generator is allowed a bit of time to stabilize for units in that low KW/KVA rating.

This calculation is for the 10 KS having a power factor of 1.0 (pure resitive load)

If the PF is 0.8, the theoretical HP will be 8000 / 746 = 10.75 approximately. Derating this by an 80% efficiency will result in a driver size equal or greater than 10.75 / 0.80 = 13.4 HP, (or 15 HP).

TexMav

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• A 15 horse power gasoline motor can easily start the generator and bring it up to speed, if the generator is seeing a high impedance.

20 horse power may not be enough, if the generator sees a low impedance = you should not expect 10 kw the first few seconds after starting.

Speed is likely 3600 rpm, so the motor needs to be capable of 20 horse power at 3600 rpm, otherwise your max sustained output will be less than 10 kw.

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