When the motor windings are distributed in the core slots, they must be embedded and connected according to a certain rule to output a symmetrical sinusoidal alternating current or generate a rotating magnetic field. In addition to some other parameters, when reflecting the law of the relative position between each coil and winding, we also need to use the concept of electrical cost. It is known from mechanics that a circle can be equally divided into 360°, this 360° is the usual mechanical angle. In electrical engineering, the angle unit for measuring electromagnetic relations is called electrical angle, which divides each week of sinusoidal alternating current into 360° on the abscissa, that is, when the conductor space passes through a pair of magnetic poles, the electromagnetic corresponding changes by 360° ° Electrical angle.

Therefore, the relationship between the electrical angle and the mechanical angle in the motor is: electrical angle α = number of pole pairs xPx360°. For example, for a two-pole motor, the number of pole pairs p=1, then the electrical angle is equal to the mechanical angle, for a four-pole motor, p=2, then the motor has two pairs of magnetic poles on a circle, and the corresponding electrical angle is 2×360° = 720°. And so on.