Simplified Motorette Test Evaluation of AC Loss in Motor Windings

With increasing operating fundamental frequencies, AC winding effects are becoming a dominant source of loss in AC machines. To mitigate for AC loss, windings formed from multi-stranded parallel conductors are commonplace, however such Litz type formations can suffer from circulating bundle losses which are difficult to model. A low cost, configurable, experimental method of characterising the AC loss behaviour of windings with arbitrary geometry and constructions is presented here. The test bench allows comparison of AC loss magnitudes for different winding designs at representative operating currents and excitation frequencies. The experimental measurements are validated against 2D FEA for rectangular section conductors over a range of size and conductivity. Further, the test setup is shown to be effective in identifying bundle level losses in multistranded conductors.