Maximum current from generator coils

[Njguy]

I'm trying to figure out the maximum current generation capacity, at a given voltage, of a series of generator coils. My theory was that if you hook up the coils to a power supply and get the current at a given voltage, say 12 volts, it will give you the maximum current those coils can generate at that voltage when the generator is running???. Assume that the voltage remains steady whatever load is placed on the generator for the sake of simplicity.

 

[crutschow]

That will give you something like the short circuit current, not the maximum current the generator can continuously supply. The maximum current is determined by the generator coil resistance and the amount of heat that can be dissipated by the coil. That's not readily determined by measurement of the coils.

 

[Njguy]

That will give you something like the short circuit current, not the maximum current the generator can continuously supply. The maximum current is determined by the generator coil resistance and the amount of heat that can be dissipated by the coil. That's not readily determined by measurement of the coils.

I had assumed that the short circuit current was the maximum current as i figured that the resistance of the coils themselves would be the current ceiling so to speak, you'd then have to wire a bunch of loads in parallel to reach it. Anyone have any better illustrations if I'm wrong?

 

[kubeek]

Yes the resistance of the coil is the ceiling for the peak current, but if you were to use it at that current continuously you would soon discover that the coil is overheating and starting to melt the insulation, hence the need to set the max current based on heat dissipation.

 

[crutschow]

Note that the maximum current, based upon the winding resistance, occurs for a short circuit, with zero volts at the output, which is not a useful operating point. The normal maximum operating output current would be with perhaps a 5% or so drop in voltage from the open circuit value. This means the minimum load resistance would be about 20 times the winding resistance.

 

[dr pepper]

If the coils are air core that applies, however if they are iron cores then saturation of the core plays a big part, I have a 50's bicycle dynamo where the core saturates not long after the wheel starts rotating, replacing its alnico magnet with neodymiums didnt increase its o/p by the diffreence in magnetic field produced by the neo's.