mcu.rar_ac motor contr_three phase motor_三相电机_矢量_矢量控制

8-bit

Rev. 2596A-AVR-06/05

Features

• Less than 5us response time on Hall sensor output change

• Theoretical maximum of 1600k RPM

• Over-current sensing and stall detection

• Support for closed loop regulation

• UART, TWI and SPI available for communication

the coils at the correct moment. In BLDC motors the commutation is controlled by

electronics. The electronics can either have position sensor inputs that provide

information about when to commutate or use the Back Electromotive Force

generated in the coils. Position sensors are most often used in applications where

and where position control is not in focus, e.g. in fans.

This application note described the control of a BLDC motor with Hall effect

Control of a BLDC motor with position sensors can be implemented on sufficiently

number of magnetic poles in the rotor also affects the step size and torque ripple of

the motor. More poles gives smaller steps and less torque ripple. Figure 2-1 shows

coils and four poles, (b) has three sets of coils and eight poles and (c) has four sets of

coils and eight poles.

the BLDC motor lighter than the rotor of a conventional universal DC motor where the

sequence in reverse order the motor run in the opposite direction. One should

magnetic field attracts and rejects the permanent magnets of the rotor. By changing

the current flow in the coils and thereby the polarity of the magnetic fields at the right

moment – and in the right sequence – the motor rotates. Alternation of the current

flow through the coils to make the rotor turn is referred to as commutation.

A three-phase BLDC motor has six states of commutation. When all six states in the

commutation sequence have been performed the sequence is repeated to continue

multiple poles the electrical rotation does not correspond to a mechanical rotation. A

number of electrical rotations is referred to unless otherwise mentioned.

Connecting the coils to the power and neutral bus induces the current flow

(accomplished using a driver stage). This is referred to as trapezoidal commutation or

block commutation. An alternative method is to use a sinusoidal type waveform. This

application note covers the block commutation method.

shown.

case it is however also recommended to have stall detection (blocked motor) and

overload detection.