Lowest emission electric motor - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: August 08, 2021, 02:43:13 pm
content: Hi,considering electric motors of sizes around those of stepper motors NEMA17-NEMA-23 and assuming the driver electronics is kept far from the motor and shielded relatively well, which type of electric motor (at the motor location) has the lowest EM emissions?I assume steppers are the worst because of the "fast" switching but maybe that is not the case?And generally what is the best way to minimise EM emissions apart from shielding the motor and perhaps adding tiny capacitance across the switching pins?Thank you

author: SilverSolder
author_rank: Super Contributor
timestamp: August 08, 2021, 04:42:19 pm
content: Some ideas out of the blue -I guess that in the case of stepper motors, you could limit emissions if you somehow controlled the waveforms that drive the motors so rise times are moderate and "corners" are smooth.For other types of motors, you could try an inductor in series with the motor to smother out current "noise", in addition to the capacitor you already mention.You could use multiple capacitors to handle different frequency bands (see Dave's videos on decoupling capacitors).

author: Benta
author_rank: Super Contributor
timestamp: August 08, 2021, 04:44:28 pm
content: Too general.PWM drive? This will make noise with any type of motor.

author: nali
author_rank: Frequent Contributor
timestamp: August 08, 2021, 04:50:28 pm
content: In the abscence of any other criteria - if it's just a motor you want without EM emissoins, consider using pneumatic.

author: ignilux
author_rank: Unknown
timestamp: August 08, 2021, 05:45:50 pm
content: Quote from: SilverSolder on August 08, 2021, 04:42:19 pmFancy motor drivers (from Trinamic, etc) have programmable settings for this (different "levels", too) for the express purpose of reducing radiated emissions. If you're not careful you can start to dissipate quite a lot of heat in your bridge transistors, though. Everything's a tradeoff!

author: Someone
author_rank: Super Contributor
timestamp: August 09, 2021, 12:40:32 am
content: Sine wave drive with the lowest practical number of poles/largest step angle.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 09, 2021, 01:28:33 am
content: Two types of motors make noise by themselves:Brushed motors emit arcing noise, impulsive / broadband with a modulation corresponding to number of poles * RPM.BLDC motors, of various types, having onboard control circuitry, which emits some switching / PWM noise.The same should be true of most any integrated control type, really, including this kind of servo and stepper motor.In general, the drive may emit considerable noise. Steppers are a common example, indeed; VFDs, with unfiltered or poorly filtered outputs, basically the sky's the limit (100s of volts, kV even for medium voltage units).Tim

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 09, 2021, 01:30:28 am
content: Quote from: nali on August 08, 2021, 04:50:28 pmHeh, or for minimal vibration as well: the actuators used on LIGO are some kind of laminar-flow hydraulics, with high bandwidth (100s Hz) and, obviously, low distortion and noise. I forget how they even do that. Linear actuators of course, not continuous motion.Tim

author: BrianHG
author_rank: Super Contributor
timestamp: August 09, 2021, 02:00:36 am
content: You can always encase your control & drive circuity in a metal case right on the motor, having the whole thing frame grounded. No exposed wires except for the power and control signals which would have choke filters to the frame ground at the connection port.Instead of fancy circuitry which may still deliver EMI under odd mechanical loads on the motor, just don't allow any EMI to escape the device.

author: dmills
author_rank: Super Contributor
timestamp: August 09, 2021, 11:01:41 am
content: I have a BLDC based design that uses class AB LINEAR power amplifiers (small audio ones) to provide the three phase drive, very quiet that, but I get more heat in the driver heatsinks then I get power out of the motor, and for that specific application that is just fine.You can do much the same thing with steppers, and even induction motors, it just costs you efficiency.

author: Benta
author_rank: Super Contributor
timestamp: August 09, 2021, 03:54:38 pm
content: Quote from: dmills on August 09, 2021, 11:01:41 amIn that case it's PMSM drive. Same motor, different drive strategy and very different characteristics. Starting a PMSM under load is a challenge.

author: Someone
author_rank: Super Contributor
timestamp: August 09, 2021, 10:43:21 pm
content: Quote from: Benta on August 09, 2021, 03:54:38 pmNot sure that PMSM is being used correctly here, a synchronous AC motor can be built with all sorts of different mechanical/magnetic arrangements, but all can be designed for sine wave drive.Stepper motors of Permanent Magnet synchronous motor (PMSM) design or the more common Reluctance motor, neither is exclusive or more suited to any specific drive waveform. Thats another free design parameter.

author: ricko_uk
author_rank: Super Contributor
timestamp: August 10, 2021, 07:08:52 pm
content: Thank you all!