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This noise can heat up the windings and reduce efficiency, while also creating an audible acoustic buzz caused by the switching frequency. Another drawback is the electrical and acoustic noise produced, mostly coming from the rapidly-switching direct current powering the individual phases. However, it does suffer from torque ripple problems. It's very common in high-speed applications or applications where a high starting torque is required, such as in power tools, vacuums, drones, and others. Its simplicity reduces design time and cost, especially in terms of processing power used for the control algorithms. It's the easiest commutation technique to implement compared to sinusoidal and field-oriented control. Trapezoidal commutation is popular because of its simplicity, low cost, and reliability. This can be done using sensored or sensorless techniques.

In order to commutate efficiently, the motor's position needs to be known so that the face currents can be turned on in sequence accordingly. Because of this, BLDC motors can be commutated using both trapezoidal and sinusoidal commutation. However, inductance in the motor smooths the back-EMF into a slightly sinusoidal shape. Typical BLDC motors are wound in a trapezoidal manner, which will theoretically produce a trapezoidal back-EMF wave form. To maximize performance, the drive current should match the back-EMF wave form. This back-EMF wave form can be trapezoidal or sinusoidal in shape, depending on motor construction. When the motor spins, it generates a counter-electro motor force or voltage that opposes the change in current which induced it. As current moves from one face pull of this stator winding to the other, the magnetic field produced pulls the rotor in its direction based on its polarity. In this diagram, we see three phase windings in the stator. The process of switching on and off the current applied to these phase windings in the stator to generate motion is called motor commutation. The coil windings in the stator will turn on in a specific manner, which will pull the rotor, essentially making the rotor chase the magnetic fields created by the stator.

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The process of exciting these windings needs to be done in a controlled fashion, which is where motor driver electronics come into play. And the rotor is a permanent magnet that reacts to the magnetic fields generated by the stator. BLDC motors consist of a rotor and stator, where the stator is made up of coil windings that act as electromagnets when current is injected into them. Let's begin by refreshing the basics of spinning a BLDC motor. In this video, we'll discuss how a BLDC motor is commutated using trapezoidal commutation, the benefits and disadvantages of this method, and how it's implemented using sensored and sensorless techniques. Hello and welcome to this TI Precisions Lab video on trapezoidal commutation of Brushless-DC motors.

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