View Full Version : ECM fan motors reverse rotation after power surge

13-08-2015, 02:07 PM
Hello everyone,
We are a small refrigerated case mfr. One of our customers is a supermarket chain that claims the 120V ECM Evap Fan motors we use in our display cases reverse rotation apparently after a power surge. We have tried to simulate the situation here in the shop, but failed to get them to malfunction. The manufacturer, Wellington, states they're not aware of any such problems. The issue has been coming up from time to time and I respect the service company that the market uses who has verified the issue however no other customers have contacted us with a similar problem.
1) has anyone ever heard of this?
2) Is there a fix to prevent it.

They are requesting, on all future case we install a relay in the fan circuit but if the relay coil is powered by the same circuit as the fan won't the effect be the same when the power surges? By the way these are continuous run fans.
Please comment . Thanks, Ken

13-08-2015, 10:16 PM
Do you have to replace the fans, if not then do the fans "fix" themselves?

14-08-2015, 04:24 AM
Not to well up on electric motors and you use different voltage than we do,but I have had a three phase motor do this when one of the phases went down,a very good friend now retired and a good engineer referred to it as ghosting?,seen posts on here about using dc motors on some cabinets.

14-08-2015, 04:27 AM
Whoops just realised you are talking about dc motors

Glenn Moore
15-08-2015, 06:58 AM
Hi Ken
I assume the dc supply is rectified from the ac mains supply. If so what electrical equipment are you using to do this is transformer, rectifier , relays etc this may help give us a clue as to what may be happening

15-08-2015, 12:29 PM
DC motors don't change rotation direction unless Dc electric supply reverses the + and -.
I would inspect the control wiring for some wiring mistake.

monkey spanners
15-08-2015, 12:37 PM
I've heard of it happening when there is a brownout, i think they usually run the correct way again once turned off and on again.

23-08-2015, 04:39 PM
Sorry for the delay in responding. Vacation ending tomorrow, got a nice tan, ate great food and caught lots of fish...
These are 120V A/C ECM motors Which have an on-board rectifier.
So, monkey spanners,
Yep during a brown-out... but maually turning them off results in a service call.
Still not sure how a relay will solve the problem...

07-09-2015, 11:12 PM
Hello Ken !
As i know an ECM motor is in fact a brushless dc motor. When starting the rotor that has permanent magnetsmoves back and forth to help the circuitry to understand the direction then speeds up in the direction programmed . Also it is sensorless and understand the direction from the rotating direction of the magnetic field when working but if some brownout occur this may erratically convert the direction .
If the process can tolerate a delay untill this fan fully stops then you can add a delay on relay that will power the fan when it fully stoped .

08-09-2015, 11:16 PM
Do they not manufacture a motor with a fan that will blow/suck whichever direction the motor turns? to stop any recurrence of your problem.

08-11-2015, 01:15 AM
Hi, Do all the motors reverse or just one or two? As I understand an Electronically Commutated Motor is a bit like a 3 phase motor supplied with power generated from an electronic circuit - akin to a stepper motor. As previously mentioned if it loses a phase (or the magnet becomes weak) then the motor can run either way. Is it being blown by the airflow from the other motors and thus starting in reverse. What happens with the motor on the bench - can it be spun and encouraged to run in either direction? (A bit like a PSC motor when capacitor goes u/s) If so then would suggest motor is faulty.