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

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Discussion Overview

The discussion revolves around the effects of changing wire gauge on voltage and current in a small generator. Participants explore the relationship between wire size, output voltage, and current under no-load conditions, as well as the implications of design choices on generator performance.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant reports measuring 50 volts at 1 amp with 28-gauge wire and 15 volts at 0.25 amps with 24-gauge wire, expressing confusion over the relationship between voltage and current.
  • Another participant challenges the notion of measuring current under no-load conditions, stating that there should be no current (0 amps) when not under load.
  • A request for a clear description of the generator design is made, emphasizing the need for diagrams to assist in understanding the setup.
  • It is suggested that no-load output voltage should be independent of wire gauge, although increasing wire size may lead to increased leakage inductance, potentially decreasing no-load voltage.
  • Participants discuss that increasing wire diameter should theoretically increase output current capability due to lower parasitic resistance, but this may depend on the number of turns in the winding.
  • One participant notes that the no-load output voltage is influenced by the number of turns, rotational speed, and magnet strength, and raises the possibility of shorted turns in the 24-gauge winding.

Areas of Agreement / Disagreement

Participants express differing views on the implications of wire gauge on voltage and current, with no consensus reached on the underlying reasons for the observed measurements. The discussion remains unresolved regarding the effects of wire size on generator performance.

Contextual Notes

Participants highlight the importance of design details, such as the number of turns and winding configuration, which may affect the generator's output characteristics. The discussion also reflects uncertainty regarding the definitions of no-load conditions and their implications for current measurement.

NY Operations Tech
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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.
 
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NY Operations Tech said:
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.
 
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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.
 
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NY Operations Tech said:
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.
 
NY Operations Tech said:
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
 

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