Brushless DC is a misnomer; there is nothing DC about them. They are 3-phase permanent magnet synchronous motors. It’s just more fun to say BLDC than PMSM, probably.
Traditionally these motor types have been vastly different and for different applications, but modern controllers have blurred the lines between them. There are still some differences. What they all have in common is the “servo” part; an encoder and feedback loop. BLDC and stepper motors are synchronous; the controller tracks permanent magnets on the rotor and produces torque by controlling current to two (2phase stepper) or three (3phase stepper, BLDC) coils. AC induction servos have no permanent magnets. They produce torque by inducing current into the rotor coils, which are arranged to produce an opposing magnetic field. Functionally, stepper motors are in a different class than the other two types. They usually have good low-speed torque and limited rpm. Think of them as a 100-pole motor. The limited RPM also limits the power output in a given envelope. Usually they can produce about one third to one fourth the power of a BLDC or AC motor of the same mass. Usually. The difference between BLDC and AC servos is more nuanced. BLDC motors tend to have more torque and better stability at low RPM. AC motors run more efficiently at high RPM. > On Jul 16, 2025, at 6:56 AM, Stuart Stevenson <stus...@gmail.com> wrote: > > What is the difference between: > > 1: stepper/servo (Hanpose, et al) > > 2: BLDC servo > > 3: A/C servo > > It seems to me to be describing the same technology. > > Thanks > > Stuart Stevenson > 4638 Farmstead Ct > Bel Aire, Kansas 67220 > 316 258 0953 > stus...@gmail.com > > -- > Addressee is the intended audience. > If you are not the addressee then my consent is not given for you to read > this email furthermore it is my wish you would close this without saving or > reading, and cease and desist from saving or opening my private > correspondence. > Thank you for honoring my wish. > > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
