Fluke 438-II User Manual - Page 19

Motor Analyzer Motor Analyzer Parameters Voltage Harmonics Harmonic currents are introduced when the line voltages applied to the motor include voltage components at frequencies other than the fundamental frequency of the supply (50 Hz or 60 Hz). The temperature of the motor operating at a particular load and per unit voltage harmonic factor will therefore be greater than that for the motor operating under the same conditions with only voltage at the fundamental frequency applied. When a voltage is applied to the motor that consists of components at frequencies other than the fundamental frequency, the rated power of the motor should be derated according to the Derating Factor shown below. The Harmonic Voltage Factor (HVF) is defined as: n = order of odd harmonic, not including those divisible by three Vn = the per-unit magnitude of the voltage at the nth harmonic frequency The total derating is found by multiplying the Derating due to Unbalance and due to Harmonics. To open: 1. Go to the ANALYZER screen. 2. Push . The NEMA Derating screen shows the Motor Load (vertical axis) relative to the advised derating due to voltage unbalance or voltage harmonics (horizontal axis). 13