BLDC Washing Machine Motor stuttering with 30A ESC - Page 1
Forum section: electronics / beginners

author: litch
author_rank: Newbie
timestamp: September 15, 2019, 07:00:40 am
content: Looking for advice.I've got a 24P 36S washing machine motor, and I rewired it from (3Y x 12S) into (3Y x 3S4P) to decrease the voltage requirements.I then purchased some 30A ESC controllers off the internet to test with.Validated the ESCs to spin up a CDROM BLDC on a 12V 50W supply.Then hooked up the ESC up to the washing machine motor and it sits there and stutters for a second or two, then rotates like 45 degress, then stutters, then rotates a bit...I thought it might be the ESC hitting current limits, but it's cold to touch and doesn't make any "error" beeps - the supply voltage doesn't dip.I thought it was a lack of power, perhaps - so I tried a 24V 8A power supply - exactly the same response.I though maybe I made a mistake on the wiring, so I energised each individual phase with 5V 20A and went around with a bar magnet - testing that each one repelled my magnet and all other pols attracted. That checked out.I'm out of theories as to what the issue is - does anyone have any more ideas?Video example of what's going on:https://youtu.be/Fg9MTuB6iQg(No Audio).I don't own any serious diagnostic equipment. I have a DMM, that's it.TIA.

author: awallin
author_rank: Frequent Contributor
timestamp: September 15, 2019, 07:05:56 am
content: sensorless (no Hall sensors?) ESC? Looks like the ESC is confused about the voltages it is seeing as feedback when it applies pixies to the coils...there must be something fundamentally different in the way your working cdrom motor is wired compared to the washing machine?

author: litch
author_rank: Newbie
timestamp: September 15, 2019, 07:14:29 am
content: QuoteYep. Same thing as you'd buy for an RC car that runs on LiPO batteries.Technically, it's a chinese ripoff of a BLHeli_32 ESC.The ESC is rated to 3S-6S (11.1V to 22.2V) so I should have been within it's input spec, but the back EMF like you mention might be throwing it off.I might get a proper 200A ESC. Was hoping to prototype this with a smaller ESC before I went nuts with the serious gear.

author: janoc
author_rank: Super Contributor
timestamp: September 15, 2019, 10:58:38 am
content: It may also be because the mass of the washing machine motor is much higher than of a typical RC motor. The ESC attempts to start a sensor-less motor "blindly" (at no/low speeds there is no usable EMF, so the start-up is open loop) and if it is programmed to spin it up too quickly (a lightweight RC motor can spin up a lot faster than a large washing machine motor) the motor is likely unable to keep up with the commutation and stalls - stutters.I had this sort of issue with some helicopter/drone ESCs too when trying to run harddisk spindle motors with them. They have the start-up time constants wrong for that type of motor and it wasn't able to start up or started unreliably. Reprogramming the ESC and changing the settings to make the startup slower fixed it.

author: Siwastaja
author_rank: Super Contributor
timestamp: September 15, 2019, 11:07:59 am
content: Quote from: janoc on September 15, 2019, 10:58:38 amVery likely the correct answer.

author: floobydust
author_rank: Super Contributor
timestamp: September 15, 2019, 06:47:28 pm
content: You can spin the motor as a generator (with a light resistor load) and scope the output waveforms, to see if your windings have the correct sequence and phase.Silicon Chip magazinearticle Feb. 2012about repurposing a Fisher & Paykel SmartDrive washing machine BLDC motor. If you have a subscription or access, it goes into good detail.