Kunstig belastning af induktionsmaskiner / Artificial Loading of Induction Machines



The full load temperature rise represents an essential performance index of induction motors. Mechanical coupling of a load machine is both costly and time consuming, especially vertically mounted motors are difficult to test. Artificial loading using a VSI is a low-cost alternative to full load testing of induction motors. The two mixed frequencies method can produce two magnetic fields rotating at different speeds. The speed of the resultant field and its amplitude are variable and the rms motor current is increased compared to the no-load current. An artificial synthetic loading is achieved in this way. The induction machine losses can be adjusted by choosing different voltage and frequency values. The experimental arrangement is based on a multiprocessor system and a Danfoss, VLT 3004, 4 kVA VSI. Tests at simulated full load have been peformed, using the proposed method on 0.75 kW and 2.2 kW induction motors. The test results verify the theoretical assumptions. In future, synthetic loading could be used in the electrical machine industry, for induction machine thermal tests and for thermal modelling at constant or variable speed. In order to obtain improved thermal protection, a thermal model of the induction machine has to be used. (Ewen Ritchie, Per Sandholdt, Frede Blaabjerg; Tutelea Lucian, Ion Boldea, University Politehnica of Timisoara, Romania)
Effektiv start/slut dato31/12/200331/12/2003