The Application of Magnetic Wedges in the Slots of Magnetoelectric Valve Engines

Abstract

The effect of magnetic wedges in a half-closed slot on the magnetic field configuration in the air gap of a brushless dc engine with permanent magnets has been examined. Based on field numerical calculations, it has been established that magnetic wedges recessed into the grooves of slots can almost eliminate the high-frequency magnetic field oscillations caused by stator teeth in the air gap. This effect takes place if the relative magnetic permeability is not lower than 40. In valve engines with magnetic wedges, the eddy currents in conductive array of permanent magnets are suppressed, causing their heating and significantly reducing reactive electromagnetic torques (sticking torques of the rotor). After installing magnetic wedges with protrusions in the slots, the amplitude of the fifth harmonic of the magnetic induction causing the losses in magnets decreases by 13 times. Such an engine has almost no losses in the magnets. The calculations of losses in the magnets indicate that without recommended wedges the eddy currents will occupy the entire volume of magnets. The maximum reactive torque with such wedges reduces by six times. Magnetic wedges with usual location in a semiclosed slot (not recessed into the groove of the slot) have a small effect on the magnetic field configuration in the air gap.