Fluke 43B
Applications Manual
50
Measuring Voltage Harmonics
When the supply voltage is distorted by harmonics, the motor can suffer from
overheating.
1
Open the main menu.
2
3
Make connections as shown below:
Look at the THD reading. In general, the Total Harmonic Distortion of the
voltage supplied to an induction motor should not exceed 5%.
Look at the harmonic spectrum.
Negative sequence harmonics (5th, 11th, 17th, etc.) will cause most
heating because they try to run the motor slower than fundamental (they
create reverse rotating magnetic fields within the motor). Positive
sequence harmonics (7th, 13th, 19th, etc.) also cause heating because
they try to run the motor faster than fundamental.
HARMONICS
Summary of Contents for 43B
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