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Originally Posted by e*clipse
Ok, now I'm very confused...
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Sorry - I do that to everyone!
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Perhaps you're talking about an induction motor? They do all sorts of things that I honestly don't understand.
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The stator or stationary part of the MGR should be similar to an induction motor - coils with inductance and resistance the adds up (vectors) to impedance? The rotor is magnets so the fields are not induced .. simpler and no weird magnetic coupling ...
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The motor that I'm using (the MGR motor) has very similar specifications to the newer (2010) Prius motors. The Prius motor is a slightly larger motor (60kW vs 50kW) with the same number of poles and very similar windings (number of wraps, wire guage, etc) The rotor is nearly identical, just scaled to be slightly larger. I'm not planning to rewind the motor, just use it as it was designed. That's why I'm stuck with the high voltage.
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OK - got it. I was wondering where the 4 pairs of poles and such came from ... my mistake ... assumptions!
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You can see there's huge amount of BEMF @ 13,000 RPM - about 475V.
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So you only get current from applied voltage minus BEMF, right?
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(BTW - how do you relate RMS line-neutral to the Bus voltage?? )
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For AC, peak to peak is your bus voltage. One phase (or 2) connected to + and one phase (or 2) connected to -. RMS is peak / 1.414
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Say you're supplying 650V, the voltage difference would only be 175V. According to ORNL's locked rotor tests, the amount of current required to get 35Nm of torque ( the motor's aximum output @ 13,0000 RPM ) is about 40A. I know it's not this simple, but just using Ohm's law says the maximum impedance for 40A would be 4.375Ohms.
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Yes. 4.375 ohms at what phase angle?
https://en.wikipedia.org/wiki/LC_circuit
It gets messy
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Now here is where I'm really confused - is there an increase in impedance -because of the increased frequency - and/or a decrease in effective voltage that limits the maximum speed? (assuming they won't physically explode) Also, to further complicate things, these motors provide a large % of reluctance torque - greater than 50% at high rpm.
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There is an increase in impedance due to frequency, and it also changes phase angle
There is a decrease in the effective voltage due to BEMF
So I guess the answer is .. BOTH
I am not going to take a shot at the magnetic circuit effects - switched reluctance design and effects seem to me to be more of a black art than actual engineering and science.