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I have a 7KVA generator which i use for multi-purpose. Some times i run AC on it and some times not. Will the generator consume less fuel when i utilize less power generated from it?

Thanks

Code Tree
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    There is no unused power. There is unused **power-generating capacity**. – Pete Becker Jul 07 '15 at 15:55
  • Has already been answered: [Putting far more mechanical energy into a generator than its electrical load](https://electronics.stackexchange.com/questions/24840/putting-far-more-mechanical-energy-into-a-generator-than-its-electrical-load) – Curd Oct 23 '19 at 12:17

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There are two aspects to control of the generator- the first is the motor RPM and that will determine the AC output frequency. That is controlled (typically mechanically with a governor) by adjusting the throttle automatically (you may be able to see the throttle linkage). That maintains fairly constant RPM as the engine loading changes.

The second is voltage regulation and that is sometimes achieved by changing the field coil current (inexpensive or small ones may have fixed excitation so the voltage will drop noticeably as the load increases).

At a very light (electrical) load, the generator is very easy to spin so the motor is essentially idling. As you add electrical load the field caused by the current flowing through the load (and the coils in the generator) starts to oppose the rotation of the rotor (Lenz's law) and it becomes much harder to spin the generator. (The voltage will also start to drop so field current also increases to maintain the voltage if the generator has an AVR- which will also increase the required torque to compensate for the internal losses).

As the load increases the motor RPM will tend to drop, so the governor opens the throttle wider, admitting more fuel and air to the engine, in order to try to maintain a constant RPM. It's probably a reasonable rough approximation to say that the fuel consumption increases linearly with kW loading above the baseline idle consumption.

TL;DR: Yes, it will suck a fair bit more fuel if you put a heavy load on the generator.

Spehro Pefhany
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Yes and it will consume more fuel when you load it.

There should be some mechanism/electronics in the generator which will keep the rpm (revolutions per minute) of the engine constant or to keep the voltage constant. If you load the generator more the rmp and or voltage will drop so the engine will be pushed harder to compensate.

If this was not so, where would the excess energy go ? It would be turned into heat which is very wasteful.

brhans
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Bimpelrekkie
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What happens to unused power in generators

Power is volts x amps and if the load is not demanding any current then there is no demand for power and no power is generated. Of course there will always be some power needed to combat the friction in the bearings of the generator and wind resistance in the spinning parts but this will be constant. Fuel is needed for this.

There will also be a bit of extra power wasted proportional to the current demanded by the load due to copper losses in the windings of the generator supplying load current.

Andy aka
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There is no excess electricity or power. However there are ways to use generated power in excess of demand but within the generating capacity. One obvious way is to charge batteries to be used when there is over demand. An interesting solution has been developed by PURE Electricity Unst, Shetland. a small experimental energy generator. Their solution is to use excess generating capacity to produce hydrogen which can be stored. The hydrogen is used to produce extra electrical power when required and also used for powering vehicals.

Alan Stackman
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