Three-Phase Motor Reversal

Could someone have worked on another motor powered from the same feed, and then swapped two leads on the main feed to make the other motor rotate correctly, thereby making this one incorrect?

Or moved your Breaker at the Distribution Board and mixed the leads when re-installing them.

Regards,
Sapper

If you can't figure out who rolled the wires then just go with the handy ghost theory. I know I've been on more than a few sites that I would swear were built on burial grounds.

Or...

Because of the type of fan, it was incorrect all along but still managed to move some air, so nobody noticed it was incorrect until you just did.

Yes, this must be the most probable reason.

it looks like what was indicated by jRaef is the probable cause. during commissioning this fault might have occured and nobody has noticed it. since it has run for a long time in opposite direction the bearing is likely to get damaged, kindly measure the vibration level during running of fan and if it is high inspect the bearings and if required replace it.

seetharaman

There is a possibility of phase reversal either during shiftig or during re-wiring, the phase sequence might have been changed. Simple rectification job is to carryout the phase reversal and close.

CVS murthy

Manager Projects

GMMCO Limited

I head about such reversal at a plant; that was due to very high harmonics in the power line generated by VFDs & SCR based DC drives.

Joe Sparky, Thanks for your input. Here is more info and an update. The fan is a reverse incline centrifugal, The fan sits in a 24"duct (the motor outside of the duct), with a butterfly damper above the fan. The fan exhausts the fumes from an Epoxy coating preparation dip tank (acid fumes). My customer swears none of his crew has worked on this piece of equipment, If that is true then they have been breathing acid fumes for four months. I, was choking just walking thru the area. My costumer originally asked me to look at the butterfly damper because it was not opening, He had just found that before I, arrived. My guess is one of his crew members worked on this fan without his knowledge and is not admitting to it. Thanks again, Phenortner

Hi again, because it is a centrifugal fan the air will always travel in the same direction, reglardless of the motor rotation, so the fumes would have been extracted anyway just not as efficently as they would have been if the motor was going the correct way.

You did not answer my orignal questions, 1; were you called back because of a motor overload? and 2; did you check the motor direction or did you only check the air flow direction? I look forward to your reply.

Cheers

Joe Sparky

Several of these ideas might be good. It is high time for the OP to give us an update.

The motor can not change the direction of rotation without interference with the phase sequence. someone must ave swapped two phases at the motors incoming or in the distribution board. nothing else can change the direction of rotation of a motor.

Unless you move from the Northern Hemisphere to the Southern Hemisphere. Motors spin the other way down there.

If you are definetly sure that the first time you install the fan the direction was right, then someone worked on the line and swap two leads, that is the only way that fan can change direction.