The slip of a 3-\(\phi\), 50 Hz, induction motor fed by 3-\(\phi\), 50 Hz inverter is 's' at fundamental frequency. At \(5^{\text{th}}\) harmonic frequency, the harmonic slip is nearly equal to
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General formula for the harmonic slip of an induction motor:
- For forward rotating harmonics (\(n = 7, 13\)): \( s_n = \frac{n - 1 + s}{n} \approx 1 - \frac{1}{n} \)
- For backward rotating harmonics (\(n = 5, 11\)): \( s_n = \frac{n + 1 - s}{n} \approx 1 + \frac{1}{n} \)
For the $5^{\text{th}}$ harmonic: \( s_5 \approx 1 + \frac{1}{5} = 1.2 \). This short approximation rule protects you from doing long derivation steps during exams!