Sciencemadness Discussion Board

Regulating a generator? Ye Olde Skewl way?

jgourlay - 17-2-2010 at 11:00

Think back to the days BEFORE we had solid-state anything, and especially solid-state invertors and power conditioning gear. How did we maintain 60hz, 120 or 240vac?

The thrust of my question is this. Let's say you have a "generator", ie. wire coils moving through a magnetic field. And let's say you have a waterfall, with a turbine connecting the waterfall to the generator. How do you actually regulate the rotational velocity of the generator, given a pulsating mechanical energy source, so that you provide a highly consistent frequency from the generator?

The same question could be asked of an all-mechanical diesel or gas engine hooked to an old school generator.

Magpie - 17-2-2010 at 11:20

IIRC they have mechanical "governors." That's about all I can remember.

[Edited on 17-2-2010 by Magpie]

bbartlog - 17-2-2010 at 11:21

I don't know what the preferred embodiment was at the time of transition to modern electronics, but here's a nice blast from the past, courtesy of Tesla, which shows an early solution to the problem:

jgourlay - 17-2-2010 at 11:26

Golden. Absolutely golden fella's. Thanks!

Contrabasso - 17-2-2010 at 12:33

Engines were/are regulated by a fan on the flywheel blowing air onto a metal flap that is linked to the throttle to control engine speed, engine speed controls frequency!

In an old generator there were brushes onto a commutator or sliprings and a controller to feed back some current through the energising winding to control the rotating magnetic field and the volts output.

In a networked generation system several Alternators will generate synchronously for which there really isnt forum space to discus the detail. However put simply, if you have a mains generator system and fix a motor to it the motor will turn, now if you actually turn the motor faster that it's running speed then it will put power back into the network. As long as one alternator is regulated then all the attached synchronous alternators will hold regulated volts too. However power distribution across different generators may cause uneven and unexpected loading and heating and even circulating currents. It is done everywhere but it has to be done with care.

Vogelzang - 17-2-2010 at 15:25

I found one of these.

jgourlay - 18-2-2010 at 05:04

A reply from another website:

Thank you for your enquiry
Automatic speed control of the prime mover, and hence the generator, was originally by mechanical means using centrifugal and other governors.
I don't know whether you "poked" this entry but see here for earlier devices.
Early small scale electrical systems were primarily DC systems where the voltage variations were absorbed by the battery.
Before the advent of solid state electronics, high current switching was possible using thyratrons. They were high power tube devices, introduced in the 1920s, the forerunner of the modern thyristor.
In grid connected systems the generator voltage and frequency are locked to the grid system. Changing the energy output from the prime mover will cause an equivalent change in the generator output power.
Wave power is a comparatively recent innovation.

I hope this helps

Barrie Lawson.

weldit - 18-2-2010 at 14:21

At work we have generators hooked up to motors. They put out DC power. We regulate the voltage with a resistor. I don't know how old school you want to go but this system has been around for a long time.

entropy51 - 18-2-2010 at 14:35

The really old school way was to feed the generator output voltage to an electric clock that had two drive mechanisms. The other drive was connected to a 60 Hz oscillator that ran off batteries connected to a charger. The turbine operator adjusted the steam admission valve to keep the clock hands moving in synchrony. This regulated 60 Hz to within a tolerance determined by the operator's attention span and beer intake. Some were much better at it than others. In those days it was less important that the mains frequency be exactly 60 Hz.