Why Does Changing Wire Gauge Affect Voltage and Current in a Generator?

[NY Operations Tech]

TL;DR

Generator wiring question

I am building a small generator. 12 - 5/8″ magnets rotating around 9 - 3/4″ diameter, 28-gauge copper enameled wire. Not under load, I am getting 50 volts at 1 amp. But when I increase the wire size to 24-gauge, I am getting 15 volts at .25 amps. I thought amps go up when volts go down.

 

[Averagesupernova]

TL;DR Summary: Generator wiring question

I am building a small generator. 12 - 5/8″ magnets rotating around 9 - 3/4″ diameter, 28-gauge copper enameled wire. Not under load, I am getting 50 volts at 1 amp. But when I increase the wire size to 24-gauge, I am getting 15 volts at .25 amps. I thought amps go up when volts go down.

Not under load with 50 volts at one amp makes no sense. If it not under load then there is no current. 0 amps.

 

[jrmichler]

Without a clear description of the two different designs, we cannot help you. A clear description includes at least one diagram that clearly shows the entire generator, including the winding design.

 

[berkeman]

28-gauge copper enameled wire. Not under load, I am getting 50 volts at 1 amp. But when I increase the wire size to 24-gauge, I am getting 15 volts at .25 amps. I thought amps go up when volts go down.

As has been mentioned, "no-load" means no output current.

The no-load output voltage should be independent of the gauge of the wire, to a first approximation. Can you make those two measurements?

(As you increase the size of the wire, leakage inductance will generally go up, so you may get a small decrease in the no-load output voltage.)

If all you are doing is increasing the diameter of the wire, you should see an increase in output current capability because the parasitic resistance of the windings is lower.

 

[Tom.G]

TL;DR Summary: Generator wiring question

I thought amps go up when volts go down.

For the same amount of power, Yes.
For the same power, the product of Volts and Amps is the same.

Have you counted the number of turns with each wire size? Are they the same?
Larger wire may mean fewer turns, especially if in the same space.

Also, no-load output voltage is directly dependent not only on number of turns but also on rotational speed and magnet strength.

There could be some shorted turns in the 24ga. winding.

Cheers,
Tom