I’m studying permanent magnet motors and I found something confusing.
Some references say “sinusoidal BLDC = PMSM”, while others distinguish them:
So my question is: Is a “Sine BLDC” essentially the same as a PMSM, or are they still different in design and terminology?

 

PMSM is better... PMSM got higher and smooth torque with higher efficiency and low noise compared to BLDC motor. And due to higher power density PMSM motor are smaller.

 

I’m studying permanent magnet motors and I found something confusing.
Some references say “sinusoidal BLDC = PMSM”, while others distinguish them:
So my question is: Is a “Sine BLDC” essentially the same as a PMSM, or are they still different in design and terminology?

BLDC (Brushless DC) is not typically sinusoidal; only one pair of the three coils are energized at any one time (DC) , typically a square wave.
The identical 3ph PMSM type is fed with 3ph sine wave.

 

I’m studying permanent magnet motors and I found something confusing.
Some references say sinusoidal back-emf and low torque ripple = PMSM”, while others distinguish them:
So my question is: Is asinusoidal back-emf and low torque rippleessentially the same as a PMSM, or are they still different in design and terminology?

essentially the same
but the magnetic systems are optimized for the type of drive they expect to get. sinusoidal describes the type of drive signal to the motor (for sinusoidal back-emf and low torque ripple) vs trapezoidal for plain-Jane six step commutation to use with a cheap BLDC with cheap glued magnets and bunched windings.
So, a BLDC designed for sinusoidal drive and a PMSM that's also designed for sinusoidal drive use the same design pattern.

 

To reiterate, BLDC - Brushless DC - is considered a DC motor due to only 2 coils energized at any one time.
Other than that, the motors are practically identical in construction.

 

Incidentally, as a side note, I have converted quite a few quality BLDC motors to servo motors by fitting a commutating encoder; this is a quadrature encoder that also has commutation track on it.
(see pic)
When backfeeding/rotating a BLDC motor, a 3-phase is generated, and these pulses are used on the 'scope in order to align the commutation.
Without the commutation included, the rotation of a BLDC motor can be rough at low RPMs, making it unsuitable for servo positioning, however, when used in conjunction with a PID controller, it can be made to rotate silkily smooth with very precise positioning.