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FEMM
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by Dr Stan Zurek

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====== 3-phase currents ======

All currents in FEEM are peak, so for RMS the values have to be scaled accordingly.

In order to set up a 3-phase system of currents, with the same value of **1 A peak** for each phase, and phase angles as indicated, the following strings should be entered in the appropriate current definition in FEMM magnetic model, with ''I'' denoting the imaginary number (I<sup>2</sup> = -1):

I1 (at 0°) = ''1''  

I2 (at +120°) = ''-0.5 + I * 0.866''  

I3 (at -120°) = ''-0.5 - I * 0.866''  

In order to use different amplitudes, these can be just multiplied by the required constant. For example, in order to achieve a current of **10 A rms** in each phase (with the same angles), the values should be multiplied by 10 * 1.4142 = 14.142 (so that the sqrt(2) scaling is also applied). Hence:

I1 (at 0°) = ''14.142''  

I2 (at +120°) = ''-7.0711 + I * 12.2474''  

I3 (at -120°) = ''-7.0711 - I * 12.2474''  

Note that you can multiply directly inside the input box, because the value will be evaluated correctly. So for example, typing in: \\ ''-0.5 * 14.142 - I * 0.866 * 14.142'' will set it to ''-7.0711 - I * 12.2474''.

{{3phase_current.png}} Setting up the complex value of I2


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Unofficial FEMM documentation by Dr Stan Zurek

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Unofficial
FEMM
documentation
by Dr Stan Zurek