Petrol Generator question

Diver300 said:

It makes perfect sense. However, it is only constant where the magnetic field is fixed. Any alternator that is intended to be used to generate mains will have some sort of automatic voltage regulator that will vary the magnetic field over a wide range.

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Yep that's what I've been told - and I've opened up the AVR in the generator. Unfortunately the AVR box is filled with some kind of permanent dielectric - there are a couple capacitors sticking out but the circuit board is hidden and there's no way of getting to it. But, I do have a wiring diagram of the generator which I've used to work out what I think is the wire that's delivering the field current to the rotor - and so I should be able to hijack that and keep the current constant, and hence the magnetic flux constant, right? That's my current thinking.

Perhaps I should upload the wiring diagram? It's in pdf form... how can I share this with you? Rapidshare or something?

It would be good to get a better idea of what's going on in the wiring diagram.

crutschow said:

Regarding a torque sensor, would it be possible to mount the generator so that its frame could freely rotate in operation? Then just mount an arm to the frame with a spring scale to measure the force on the arm. Simple multiplication of the arm length from the shaft to the scale times the measured force gives you torque.

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The mechanical guys have looked at that and decided it's not possible. I'm afraid I can't explain why, but they are confident that it's not an option. In fact they're confident that it's not possible to measure the torque mechanically before the generator is decoupled from the engine.

Thanks.

breakshift said:

The mechanical guys have looked at that and decided it's not possible. I'm afraid I can't explain why, but they are confident that it's not an option. In fact they're confident that it's not possible to measure the torque mechanically before the generator is decoupled from the engine.

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Well, the generator housing obviously has to be decoupled from the engine so it can freely rotate. But you certainly can measure the shaft torque by measuring the rotational reaction force on the generator housing (the prony brake technique). The only error in the measurement would be any friction in the rotation of the generator housing.

Ok after discussion we're going to go for the generator-in-reverse option - drive it as a motor. I have another question though, regarding the AVR in the system. In the wiring diagram shown below, what does the 'Vice winding' do? I understand what the AVR does - takes feedback from the generator terminals and changes the rotor field current to try and keep the output voltage constant-ish. But what role does this vice winding play? I can only think of one reason - that it takes some current from this winding, rectifies it and uses it as the field current.

**broken link removed**

Any ideas?

Bump... anyone know what the 'vice winding' is for?