Electric Generator III

Offers industrail electrical generators, backu power & diesel electric generators its basics, principles & guide.

Electric Generators and electrical materials are conductors (that allow an electrical current to flow easily) and insulators (that don't). In reality nothing is a perfect insulator or a perfect conductor: most materials have a certain degree of resistance, and lie on a scale somewhere between a perfect insulator and a perfect conductor. Materials with high resistance tend to be insulators; those with low resistance tend to be conductors. Even copper electrical cables have a certain amount of resistance. Resistance is measured in ohms, which is either abbreviated to `', or to `R' if your word processor doesn't have a `' symbol.

The mathematical symbol is the letter `R' as well. One ohm is a lot of resistance in electrical practice; we normally like our electrical conductors to have resistances much less than an ohm, for reasons that will be explained.

Electric Generator Store

In the UK (and everywhere else, as far as I know), electricity is distributed around the country in the form of alternating current. This means that the flow of electrical current changes direction, usually 50 or 60 times per second. There are two reasons for this, both historical.

First, electrical transformers (which we need to change voltage, see below) only work with alternating currents. Second, we generate electricity by spinning wires around inside magnets (this is a bit of a simplification, of course), and this naturally produces an alternating current. At the points where the current is about to change direction, there will (for a short time) be no current flowing at all. `Alternating current' is usually abbreviated to `AC'.

The fact that current is alternating has little practical impact on domestic wiring. If you grab a live conductor you'll get a shock which is just as unpleasant even though, in principle, part of the time no current will be flowing. One area where the alternating nature of the electrical supply is apparent, however, is in the use of fluorescent lights. Incandescent (filament) bulbs generate their light because the filament becomes white-hot.

It cannot heat up and cool down as fast as the alternation of the electrical current, so the light is fairly constant. Fluorescent lights, on the other hand, produce a detectable flicker at the speed of the supply alternation.

The light from a fluorescent tube will `pulse' about 100 times per second (50 times with the supply current in one direction and 50 in the other). We can't normally see this flicker, but it does tend to make rotating machines look as though they're standing still, or going backwards. This is why we are warned not to use drilling equipment, for example, in strong fluorescent light.