Diesel Electric Generators II

Basic principles of diesel electric generators, & backup electric generators & electricity to help you know more about diesel electric generators & electricity.

The basic principles of Diesel Electric Generators and electricity, You'll not be surprised to learn, I hope, that these important quantities - voltage, current and resistance - are related. It turns out that the voltage can be found by multiplying the current (in amps) by the resistance (in ohms). In symbols this is
V = I R

If algebra puts you off, don't worry, it says exactly the same thing as the `voltage is current times resistance', but in a shorter format.

In case you're interested, this simple formula is called `Ohm's law', and is probably the most important thing ever discovered in electrical engineering. In domestic wiring, `V' will nearly always be `230' (volts), so in practice we usually want to work out current (knowing resistance), or vice-versa. We can write Ohm's law in two different ways:
I = V / R

and
R = V / I

So if we have, say, a lightbulb which has a filament with a resistance of 500 ohms at running temperature, what current flows in it? Since we know that I = V / R and V is 230, and R (resistance) is 500, then I is 230/500, which is 0.46 amps, or about half an amp.

It may help to understand these relationships by comparing them to a system that may be more familiar. Figure 2 shows a water tank suspended off the ground, connected to a length of pipe. Because the pipe is open at the end, water will run down in and make a puddle on the floor.

In this system, the height of the water tank is analogous to the voltage. If we double the height of the tank (from the end of the pipe), this is equivalent to doubling the voltage. If we do this, all other things being equal, the water will flow down the pipe twice as fast as before.

This is why, if you have a water tank in your attic, you will usually get a greater flow of water from a downstairs tap than from an upstairs tap: the height of the water tank above the tap is about twice as large.

The flow of water through the pipe is analogous to the flow of current. If we double the voltage, we double the current (if the resistance remains constant).

In this system, the height of the water tank is analogous to the voltage. If we double the height of the tank (from the end of the pipe), this is equivalent to doubling the voltage. If we do this, all other things being equal, the water will flow down the pipe twice as fast as before. This is why, if you have a water tank in your attic, you will usually get a greater flow of water from a downstairs tap than from an upstairs tap: