Author Topic: F&P stators are >82% efficient as a PMA.  (Read 269 times)

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DaveP68

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F&P stators are >82% efficient as a PMA.
« on: November 30, 2017, 12:20:26 AM »
Today setup a new test rig inspired by SparWeb to more accurately measure the power output efficiency of a Fisher & Paykel smart drive stator as a PMA.

The preliminary results are about 82 % efficiency which I already knew to be in that range.

My test rig is a bit of a crude set up using a Smart Drive motor control module to drive a stator connected on the same shaft to another stator used as a PMA into a resistive load.

Here is a photo of the test rig.


Power input meter reading.


Power output measurement volts and amps.


That's 286.2 W input for a net output of 179.1 W, a very good result for my first attempt. With further refinements expect to get an even better result.

The estimated efficiency of the motor controller is 93 % which leaves the 2 stators with an approximate 82 % efficiency each.

Hope this is of interest to anyone wanting to use the F&P stator(s) on a wind turbine build.

It is possible to extract >1250 W at 500 RPM from a single F&P stator. If more power output is required just add more stators to the same shaft.
« Last Edit: November 30, 2017, 12:27:15 AM by DaveP68 »
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SparWeb

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Re: F&P stators are >82% efficient as a PMA.
« Reply #1 on: November 30, 2017, 12:55:02 PM »
Dave,
Great work!   :D

If you were to run it at several speeds, and plot a number of points, a graph like this should emerge:



I think it's pretty common for efficiency to peak and then drop above a certain speed for most motors and generators.  When the power goes up, the resistance losses go up.  Since the R*I^2 is increasing squared, it's going up faster than the power output, eating up a larger portion as the speed increases.

You could be close to the peak power point at 82%, but trying some different speeds might allow you to find even better.  You're certainly doing really well compared to my typical motor conversions.  To make the graph above, I was testing in to a battery load (not a resistive one) which clamped the voltage down and there's a big penalty in efficiency doing that.  But that's the intended purpose (wind turbine charging a battery bank) so I was being as faithful as practical.  I believe a Smartdrive would suffer a similar penalty, but who's to say it would be as great as what I lose into my batteries?

A word of caution: I doubt that the efficiency of Smartdrive 1 (driven by the F&P controller) is close enough to the efficiency of Smartdrive 2 (driven by shaft as a generator to a resistance load) for them to be divided equally.  I can't guess which would be more, but I do expect them to be different - and for the difference to change at different speeds.
No one believes the theory except the one who developed it.  Everyone believes the experiment except the one who ran it.

System spec: 135w BP multicrystalline panels, regulated by Xantrex C40, DIY 8ft diameter wind turbine, regulated by Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024