Calculating Power Output from 3 phase motorcycle stator

[bmccrary]

Hi all,

I am working on calculating the power output from a 3 phase motorcycle stator. I have had the stator rewound, looking for a little more overall output over the stock set up.

With the bike running and and the stator disconnected, I have measured the AC voltage coming from the stator from all three pins. (assuming each pin is a different phase?)

In addition I have measured the resistance across the stator.

Is there anyway to determine the power of the stator before its goes to the rectifier/voltage regulator and becomes DC?

The factory specs call for the bike to produce 310 watts at 5000 rpm. I have measured the voltage at idle (1200 rpm), 2500 rpm and 5500 rpm. These ac voltages were 23.5, 35 and 83 volts respectfully. In addition the resistance in the stator was found to be 0.5 ohms.

-bryan

 

[dpc]

You need to measure the current and voltage and power factor. If you measure the output dc current and dc amps at the alternator, the ac power output will be somewhat more than the I x V on the dc side, due to the conversion losses.

 

[rbulsara]

Also an alternator will produce power only as needed. So power measurement would only indicate what it is producing at the time of measurement based on what is being served at that time.

In order to verify if it will produce 314 watts or more, you need to apply that much load and measure.

Rafiq Bulsara

http://www.srengineersct.com

 

[itsmoked]

The effort to measure it pre-rectifier would be huge, not worth the hassle.

Make a saltwater rheostat and measure voltage and current on the rectified side. Use a true RMS meter.

Read your voltmeter and adjust the rheostat until you have 14V.

Measure the current.

Change speeds and repeat.

Beware your alternator may have a power limit. If you set all this up and run at elevated speeds with maximum current you could burn up the alternator as its loses increase.

If you were to rapidly go from cold to speed with everything pre-adjusted, you would find that the voltage would decay as the alternator warms up. As it decays about 5% that would be the most you'd probably want to happen. That value would like be the same over all the higher speeds. That would be your maximum current you'd want to extract.

That test would not work with a saltwater rheostat but would need an appropriate mechanical resistive loading method. (saltwater rheostats change to much with temperature)

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

The rated wattage may be dependent on the alternators ability to withstand the internal heating. It may be capable of producing more than the rated wattage but with a reduced life.
With too much load, the expected life may be reduced to hours or minutes.
Heating depends on I²R. If the resistance after the rewind is less than before, you can probably increase the load until your I²R is the same as before.
If your rewind did not reduce the resistance of the stator, you may not be able to increase the safe maximum power output.

Bill
--------------------
"Why not the best?"
Jimmy Carter