# Force Needed to Turn Generator at Maximum Output

1. Mar 11, 2009

### Giesick

Hi I was hoping someone could tell me the approx. amount of radial force needed to keep a 10000W generator turning while producing maximum output if there is a 1ft pulley connected to it that does the turning.
Thanks

2. Mar 11, 2009

### mgb_phys

There shouldn't be any radial force to keep a generator turning.

Energy is force * distance, and power is energy/time.
So if you have a 1 metre radius drive wheel on the turbine and a force of 1 newton at the edge pushing it around then the energy for each turn will be 2*pi*1 = 6.3 Joules, if you turn it once/second you will get 6.3Watts.

3. Mar 11, 2009

### Giesick

When generator has a load on it, it becomes more difficult to turn. So how many N do you need to turn it while it produces 10000W if the drive wheel is 0.3m?

4. Mar 11, 2009

### mgb_phys

I could turn it at one rpm with 10,000N or at 60Hz with 2.8N
Depends on the generator - normally they are designed for a particular speed which depends on the electricty frequency, the number of phases and the generator design.

5. Mar 11, 2009

### Staff: Mentor

Assuming perfect conversion of mechanical to electrical work, power=rpm*torque. You should be able to take it from there.

6. Mar 11, 2009

### Giesick

So if there are 746 watts/horsepower for turning it and the generator frame is 78% efficient. What would the motive force be for my 10,000 watt goal.

7. Mar 11, 2009

### Staff: Mentor

C'mon, make an attempt to calculate it with the formula given! This site is for learning, not spoon feeding!

8. Mar 11, 2009

### Dr.D

Power = rpm * torque only in some amazingly bastardized units!

Power = omega * T = (2*pi*rpm/60) * Torque

in more conventional SI units.