Contents
How commutation happens in BLDC?
Put simply, commutation is the process of switching the current in the motor phases to generate motion. Brushed motors have physical brushes to achieve this process twice per rotation, while BLDC motors do not, hence the name. Due to the nature of their design, they can have any number of pole pairs for commutation.
What is six step commutation?
Six-step commutation, also known as trapezoidal commutation, is a commutation technique used to control three-phase brushless DC (BLDC) permanent magnet motor. It controls the stator currents to achieve a motor speed and direction of rotation.
What is block commutation?
Block Commutation Operation with digital Hall sensors: Whenever the rotor magnetic poles pass near the Hall sensors, they give a high or low signal, indicating the N or S pole is passing near the sensors. Based on the combination of three Hall sensor signals, the exact sequence of commutation can be determined.
What is motor Hall?
A Hall Effect Sensor is a widely used sensor that provides rotor position feedback to a motor controller. Let’s understand the significance of this sensor in an automotive motor control system. In brushed motors, the brushes come in contact with the commutator and switch the current for the movement of the motors.
Which is the best commutation method for BLDC motors?
This is why BLDC motors can use either trapezoidal or sinusoidal commutation methods. While trapezoidal commutation is the simpler of the two methods, it produces significant torque ripple at each commutation step (every 60 degrees).
How are three sine waves used in BLDC?
In sine-wave BLDC control, you want to supply the motor with 3 sine-waves 120 degrees offset from each other. If you would try to do this with just an analog voltage, it would prove very inefficient. Thus modern motor controllers apply a PWM signal and let the motor filter it.
What is the sum of the three currents of a BLDC motor?
According to Kirchhoff’s current law, the sum of the three currents must be equal to zero, so the current in the third motor winding is the negative sum of the first two (to maintain a zero sum of the three), and therefore, cannot be controlled directly. Block diagram of sinusoidal commutation for a BLDC motor.
What are the downsides of sinusoidal commutation?
The downside of sinusoidal commutation is that it becomes inefficient at high speeds. The faster the motor turns, the higher the frequency of the sinusoidal signals, and controllers have difficulty tracking these high-frequency signals.