Many friends of the brushless motor pole logarithm is not understanding, and is not clear how to identify and detect the specific, in order to figure out this knowledge, Vacuz to give you a science, I hope it can help you!

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By detecting the change of rotor pole magnetic field to identify the pole pair of brushless motor, rotor magnets are arranged alternately by N pole and S pole, when brushless motor Hall detects the magnets jumping from N pole to S pole, or S pole to N pole, Hall’s output will have corresponding high and low level changes, which means the rotor position has changed, whether the brushless motor winding is energized has no effect on Hall detection.

The rotational speed of brushless motor magnetic field, also called synchronous speed, is related to the frequency of the three-phase current and the number of poles p. If the stator winding has only one pair of poles (pole pair p=1), i.e. only two poles, for a rotating magnetic field with only one pair of poles, the three-phase current changes once and the synthetic magnetic field rotates once. In case of 50hz AC, the synchronous speed of the rotating magnetic field is 50 rpm or 3000 rpm. In engineering technology, it is commonly used to rotate at r/min. If the magnetic field synthesized by the stator winding of a brushless motor has two pairs of poles (pole pair p=2), i.e. four poles, it can be shown that the synthesized magnetic field rotates 180 degrees in space for one week of current change. From this, it can be deduced that the synchronous speed per minute of the rotating magnetic field of the P pair of poles is n = 60f/p.

When the number of poles of the brushless motor is certain, if the frequency of the alternating current is changed, the synchronous speed of the rotating magnetic field can be changed, and this is the basic principle of frequency regulation. Because the magnetic poles of a motor appear in pairs, they are often expressed as pole pairs.

The brushless motor senses the change of magnets by Hall element to determine the position of the magnetic pole pair of the brushless motor, and the rotor of the brushless motor is driven by the controller to detect the speed of the magnetic field and the magnetic pole pair.

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The above is the identification and detection method of magnetic pole pairs of brushless motors. Only with a full understanding of the basics can we better learn brushless motors and master these basic methods.

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