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Old 09-16-2014, 09:08 PM   #1115 (permalink)
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Sorry about my confusion

Regarding FOC,
You're assuming you've already worked out Valpha and Vbeta, that intermediate axis that's crucial for the process? I think that's done with the inverse Park transform, correct?

Thanks for letting me know how those lookup tables work. Since you can't make a chart that covers everything, you average the rest?



Originally Posted by MPaulHolmes View Post
It would take maybe a day of getting a good resolution graph from the waveform, and building a lookup table, where the index of where to look in the table is the A/D value, and the content of the table is the angle. But that would only get you angles where the function is one to one. So, for sine, it would only work from -pi/2 to pi/2. Then, the other table can have just -, 0, + for the other function (is it negative, 0, or positive). From that, you can know the angle, since sin is positive and cos is positive in Q1, sin is positive and cos is negative in Q2, sin and cos are negative in Q3, and cos is positive and sin is negative in Q4.

The SVM doesn't make use of sin and cos at all. It just has Va, Vb, and Vc, which are the voltages along 0 degrees, 120 degrees, and 240 degrees.
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