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Why BLDC motor back EMF is trapezoidal?
We have seen that the principle of the BLDC motor is, at all times, to energize the phase pair which can produce the highest torque. To optimize this effect the Back EMF shape is trapezoidal. The combination of a DC current with a trapezoidal Back EMF makes it theoretically possible to produce a constant torque.
Why the shape of the EMF waveform of a BLDC is trapezoidal?
The geometry of the windings in a BLDC motor give it a trapezoidal back EMF waveform. The shape of a motor’s back EMF is important, because it determines what type of drive current and commutation method should be used.
Which is more sinusoidal back EMF or trapezoidal EMF?
Inductance in the motor smooths the back EMF into a more sinusoidal shape. And since the back EMF is more sinusoidal than trapezoidal, it is possible to use sinusoidal commutation with BLDC motors.
Is the BLDC a trapezoidal or sinusoidal motor?
The ability to use trapezoidal or sinusoidal commutation, or field oriented control, makes BLDC motors applicable to a wide range of applications with options to balance performance requirements with control complexity and cost.
What’s the difference between sinusoidal and trapezoidal control?
Sinusoidal and trapezoidal control references the method of commutating the BLDC motor. The BLDC motor can be pictured as a 3 cylinder engine with a hard crankshaft between them. To make the Engine move you fire your spark plug at the top of the cylinder to ignite the fuel and push the engine down and rotate the shaft.
Which is an AC motor with a trapezoidal back EMF?
But many engineers argue that brushless DC (BLDC) motors are actually AC motors, because they are driven by DC voltage that switches from one stator coil to the next, generating an alternating (hence, AC) trapezoidal or quasi-square waveform. Another way to classify motors is by their back EMF profile.