What is a Brushless Motor (2)

There are three main types of rotor position detection methods:

・ Current detection
Beyond the scope of today’s e-Learning, current detection is necessary for field-orientated control.

・Hall sensor detection
The rotor position is detected by the magnetic field of the rotor using three Hall sensors.

・Induced voltage detection
The rotor position is detected by the change of induced voltage generated by the rotor rotation.
This is one of the methods for the position detecting of a sensorless motor.

There are two basic control methods for brushless motors. There are other control methods that require complicated calculations such as vector control and weak field control.

・Square-wave drive
The rotor is rotated by switching the ON/OFF state of the inverter circuit according to the rotation angle of the rotor and then changing the current direction of the stator coil.

・Sine-wave drive
The rotor is rotated by detecting the rotation angle of the rotor, generating three-phase alternating current with a phase shift of 120 degrees in the inverter circuit, and then changing the current direction and size of the stator coil.