A generator with 2 poles spinning at 3000rpm

[leeco]

When I turn the power up on the generator up does it make it spin faster and could I take the motor off my generator and adapt my boat engine that spins to power my generator with a BMX wheel adapted?

Its not me asking this as I know the answer but my brother will not listern to me.

 

[Alarm]

Err, yes a generator gets "faster" when it has a higher demand.
But making one go faster will not give more power once past a certain amount.

So get a bigger one.

 

[leeco]

But it doen't spin faster? I thought it increased the magnetic field strength so the engine needs to give it more torque to keep it spinning at 3000RPM.

 

[ricicle]

A generator does not spin faster when load is increased (otherwise the frequency would increase and damage certain equipment)
It will need more input power (fuel) to overcome the torque in the generator caused by the increased magnetic fields.

 

[leeco]

Cheers. My brother is stripping a generator at the moment and has some crazy idea that the engine that spins at defferent speeds will power the generator with a bike wheel as a pully but I have asked him how he will get it to spin at 3000RPM but hes stupid.

 

[Alarm]

So

The more torque applied to something, the faster it will usually spin. Decrease the torque applied to something, and it will usually slow down.

But agreed the torque will be set and stabilized at an average of 3000rpm.
Hence the "spin up" and increased revs. As demand requires.

Or have not many of you used smaller type generators.
I have to admit my friends http://www.easupplies.com/GENERAC-QT15068KVAC-Automatic-Standby-Generator-p/ot11i2.htm is stable. However I thought we were on about a baby.

 

[AdrianUK]

For a standalone generator....

the speed of rotation sets the frequency of the generated electricity....for a 2 pole machine, spining at 3000rpm it will be 50Hz

the strength of the magnetic field inside the machine sets the generator terminal voltage - stronger field = higher voltage for a given machine

The powet coming out of the machine can only come from the prime mover (eg. the engine) - taking more power out of the alternator means that the prime mover must work harder ..... the governor must open the fuel value to allow more fuel if the revs are not to decrease.

Things are slighly different for an alternator operating in parallel with a stiff grid - but thats a topic for another day!

 

[leeco]

He give up in the end. I can see where he is coming from with the boat engine spinning while we travel but I told him thats what the alternator is for but he wanted to make the geny work and give 240v off the boat engine with a pully system. I have been told it is possible but would cost quite alot of money. He bought a BMX wheel.

 

[ericmark]

There are inverter generators where the inverter changes the frequency so output is always 50Hz what ever the generator speed these are used in boats so the main engine can run at any speed but the alternator output remains steady.
There are also energy saving generators which have a current sensor so when there is no load the generator ticks over at low revs but as soon as there is any load it revs up to speed to give 50Hz.
There are also portable inverter generators which will change revs according to load here the engine revs rise with load and again the inverter corrects the frequency.
We did look at the idea of an inverter generator for the boat but to fit we would need to lift out the main engine and fit a modified front pulley as it uses 5 drive belts to Travel Power Alternator as the lower the revs the higher the torque it was not the price of the unit but the cost of fitting which put us off. From internet it seems the Electrolux travel power alternator may have been discontinued?

However I would expect it was one of these units he had seen and the big thing is the inverter without the inverter the need to keep near constant revs the difference between full load and light load revs is called droop and it is this droop which allows one to parallel up generators.

 

[JohnD]

if it spins too fast, it will wear out the bearings, or burst.