PMSM vs BLDC
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BLDC Motor – Brushless DC Motor
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PMSM Motor – Permanent Magnet Synchronous Motor.
So both BLDC (Brushless DC) and PMSM (Permanent Magnet Synchronous) motors are electric motors that use permanent magnets to generate torque (rotational force). However, they have some key differences:
Control method:
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BLDC: Uses simpler control with square wave current. This leads to a trapezoidal back-EMF (electromotive force) waveform and some torque ripple (uneven torque output).
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PMSM: Uses more complex control with sine wave current. This results in a sinusoidal back-EMF waveform and smoother torque output.
Stator windings:
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BLDC: Uses concentrated windings which are simpler to manufacture but contribute to the trapezoidal back-EMF.
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PMSM: Uses distributed windings which are more complex but create a smoother sinusoidal back-EMF.
Cost and performance:
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BLDC: Generally lower cost due to simpler design and control. However, it has lower efficiency and higher torque ripple compared to PMSM.
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PMSM: Offers higher efficiency and smoother torque but at a higher cost due to the more complex design and control requirements.
Applications:
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BLDC: Commonly used in applications where cost is a major concern, and some torque ripple is acceptable. Examples include fans, pumps, power tools, and drones.
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PMSM: Preferred for applications requiring high efficiency, smooth torque, and precise control. Examples include electric vehicles, robotics, and industrial automation.
Here's a table summarizing the key differences:
The above content partially references a blog post written by Vaibhav on May 29, 2019, on web of embitel.
How PMSM and BLDC Motor work?
1. Brushless DC Motor
A Brushless DC motor is an upgraded version of a brushed DC Motor. The absence of brushes gives BLDC motors the ability to rotate at high-speed and increased efficiency.
Highlights of a BLDC Motors:
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It has two major parts- a rotor and stator.
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Rotor is the part that moves and has Permanent Magnets as Rotor Magnets.
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Stator is the Stationary component and is made up of Coil Windings.
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Electric Current through the Stator Windings generates a magnetic field which rotates the Permanent Magnet of Rotor.
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By varying the Current flowing through the stator, the speed of the Motor can be varied.
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In most Appliances, Consumer electronics, Industrial automation, Automotive Applications, the Motor Speed is controlled electronically, using a BLDC Motor Controller.
Advantages of BLDC Motor:
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Ability to work at higher speed and produce constant torque
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Durability
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Efficiency of almost 85-90%
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Ability to respond to the control mechanisms at high speeds
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No sparks and less noise, as the brushes are absent
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Ease of Motor Control (using BLDC motor controller solutions)
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Ability to self-start
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Gets cooled by conduction and requires no additional cooling mechanism
2. Permanent Magnet Synchronous Motor
Moving on to the Permanent Magnet Synchronous Motor, it can be seen as an AC counterpart of the Brushless DC motor.
PMSM also comprises of a Permanent Magnet as a Rotor and a Stator with a Coil wound over it. The working of PMSM Motor is also quite similar to the BLDC motor.
However, the change lies in the waveform of the Back EMF which is sinusoidal in nature. This is so because the coils are wound on the Stator in a Sinusoidal manner. It also implies that PMSM requires Alternating Current (Sinusoidal in nature) to achieve the best performance. This type of drive current also reduces the noise produced by the motor.
Advantages of BLDC Motor:
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Higher efficiency than Brushless DC Motors
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No torque ripple when the motor is commutated
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Higher torque and better performance
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More reliable and less noisy, than other asynchronous motors
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High performance in both high and low-speed operation
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Low rotor inertia makes it easy to control
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Efficient dissipation of heat
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Reduced size of the motor