Abstract
The small squirrel cage three-phase induction motors have been used in all fields of industries for many years. Recently, further detailed studies about magnetic noise and stray load losses have been urged in relation to noise reduction and energy saving.
Searchcoil voltage on stator and rotor were analyzed for frequency and harmonic flux orders, and its derivation were experimentally clarified. As a result, it was confirmed that time and space saturation harmonic flux had a different order and rotor mmf. included harmonic fluxes caused by stator harmonic fluxes.
From experimental comprehensive analysis of harmonic magnetic fluxes, it was found that it was enough for harmonic flux to consider up to order 5.
Experimental formulas were also confirmed to evaluate magnetic flux in the airgap due to stator mmf., permeance of airgap and slots, and iron core, considering saturation of iron (time and space separately). The formulas of magnetic flux due to rotor mmf. induced by current which depends on stator mmf. were similarly derived.
The frequencies and magnitude of magnetic fluxes such as time, space and saturation (time and space) harmonic fluxes calculated by these formulas were examined with experimental results.
As a result, most frequencies of magnetic fluxes of induction motor could be predetermined with these formulas.
