Working Magnetic Motor on you tube??

[Omnibus]

Maybe more telling will be to measure the transient voltage x current to get the rotor spin from 0 to 400rpm (which is the rpm due to the researcher's input). Integrated it would give the input energy. Gain in energy at 1200rpm (energy obtained from within, out of nothing) would be the difference of the integrated voltage x current curve (mostly horizontal also in the actual experiment, I suppose) integrated over, say, 1 hour minus what we got for the input energy.

[Dyamios]

Well you'd have to have a suitable equation for waste energy with regards to time 't'. Then after measuring how long it takes to get up to speed (time 'a'), you merely integrate the function from 0 to a, and the resulting value would be in some energy unit similar to Joules (that is, it could be converted without mis-matching temporal units).

Most motors have datasheets with efficiency curves (atleast I think they do), which often present some type of graph. Once you figure out the degree of the function presented, you can calculate a regression model using points presented on the graph. Then its as easy as integrating the function.

Hope that helps 

[Omnibus]

I though that's what I suggested above but I may be wrong.

[Dyamios]

Oh ok, your latter post would indeed be more telling. Although the energy calculated to spin up to 400rpms and then to 1200rpms would still be a bit off due to heat loss (thats all I'm really worried about).

I'll look for a generalized equation for DC motor efficiency.

EDIT: Sorry Omni, posted it before I saw it =P

[Dyamios]

Alright, here's what I found to be the equation for efficiency:

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efficiency = (Torque in in-oz)*(speed in rev/sec)/((current in amps)*(voltage in volts)*22.5)

The only issue is finding out what the torque is (given there is no data sheet) and measuring current and voltage accurately over time.


But in order to find the energy in Joules that was imparted as useful energy, you would have to integrate a different function incorporating the immediate energy being used:

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Useful Energy = (((Torque in in-oz)*(speed in rev/sec)/((current in amps)*(voltage in volts)*22.5))*((current in amps)(voltage in volts)))



EDIT: I've just read that standard DC motors generally have an efficiency of around 50%, with brushless coming in around 60%. Thus it is critical that we calculate accurately instead of merely using current*voltage, as that would be wayyy off.