Other way to measure DC output power at low cost

[jovimon]

Hi everyone, I'm building a wind turbine with a DC motor as a generator, and need help to measure the power the engine is generating at different RPM´s. It is well known that there are watt-meters (but quite expensive), it would also be possible by connecting the generator outputs to some resistances and thus measure the amperage (multiplied by the voltage generated, would the amount of watts), which require resistances very big to manage 2.62 KW (3.5 HP DC motor at 90 volts).
Anyone have an idea on how to do it at low cost?

 

[Greeshu]

You can use multimeter, it's cheap. Measure Voltage(V) and Current(I). Use Power=V*I to find power.

 

[chuckey]

You can make a big ressstor by having a saturated solution of glaubers salt. The actual resistance will be set by the dimensions of the electrodes and the distance between them. The power is dissipated as heat so after some time the solution boils and you have to add some more water. But with a tank of a few litres it would give you ten minutes or so to make your measurements. You could look for a scrap electric shower unit. These have a 7-10 KW heating element but need to be water cooled, old electric fire can provide resistance wire that can run up to red heat. Just don't kill yourself doing this experiment. :-(
Frank

 

[jovimon]

Thankyou Frank, those are clever clues.