Brushless motor, external AC voltage source, and electric power steering device

A brushless motor comprising an armature constituted by an armature core having armature windings of a plurality of phases, and a field pole constituted by a field pole core having a plurality of permanent magnets, wherein

• a voltage, in which at least either of a 5th order harmonic component and a 7th order harmonic component is superimposed on a 1st order fundamental wave of an applied voltage under a predetermined phase difference condition and an amplitude condition such that a 1st order fundamental wave peak of the applied voltage is made larger than an applied voltage peak, is applied to the armature windings;
• a harmonic voltage superimposed on the armature windings is the 5th order harmonic component and the 7th order harmonic component;
• and
• the 5th order harmonic component and the 7th order harmonic component have a phase difference of 120° to 240° with the 1st order fundamental wave of the voltage, where one period of the high-order harmonic component is taken as 360°, and a ratio of a sum of amplitudes of the 5th order harmonic component and the 7th order harmonic component to an amplitude of the 1st order fundamental wave of the voltage is 2% to 36%.