MOTOR PROBLEMS

[kaptnkirk]

I have been experiencing fresh out of the box motor problems. I went through 3 condensor fan motors to get a good one 3 weeks ago and now I am having the same problem with a blower motor at the same location. I have ordered the 3rd one today. These motors are drawing just over full load amps and go out on internal overload. Rated 460/3ph. Supply voltage 480. These motors are factory replacements from 2 different mfg's. I have wired motors from 5w to 10,000 hp and I am considering taking an office job at this point. Any Input??

[maxster]

do 480V-3 phase motors exsist

[Six]

Yes. I've got buildings full of them.

I had some issues with Carrier blower motors for a week or two.

[kaptnkirk]

I hate to name them but the condensor issue was a liebert that would run ok until it hit 90 degree's outside then off on internals every 2-3 hrs. This Trane blower motor opens internals after 2-3 mins. These units were installed in 97. I am at a loss and I might switch to another mfg of motors. The Liebert has ran fine for 3 weeks now at even 100 degree ambient.

[kaptnkirk]

We put a smaller than factory supplied pulley on motor to drop amperage. No freeze-ups as of yet. Didnt get a report on actual CFMs.

[coolinman]

Have you checked for voltage imbalance on your 3 phase 480. I would also look for poor connections. For years I took care of a facility - 7 buildings 2500 tons of air mainly 10 ton split's mostly 480 volt three phase. You can have one leg with a bad connection. You need to check while their running. The problem wont show without a load and will get worse the higher the load. Problem can be in any disconnect up to the equiptment - I've also had breakers, contactors, relays with a bad leg (resistive). One time the whole building was imbalanced from a problem at the sub station feeding the building. Followed the imbalance back to the 2,000 amp main at the switchgear feeding the building. Had to have the plant electrician call the power company - it was in their auto-transformer. Imbalances can cause high amps and big increases in winding temp.
Shouldn't be more than 2% from average A-B, A-C, B-C.
Just a thought !!

[kaptnkirk]

Thanks Coolinman..They did just have a voltage problem on two new 20 tons. Electrician wired up 208 volt units to this sweet 480 volts here and fried the transformers and????..Haha They are still trying to figure out what to do with these package units. Probably get dumped in my lap eventually.

[Six]

Your building would have to have both 3 phase 208 .

[Nuclrchiller]

If a blower motor is pulling high amps you may want to check for excessive air flow.

[Workin4TheMan]

One of my customers has a company take thermal images of all the panels in the building and the panels on the roof tops. I get a call once a year to come and change a few contactors and terminals cause they showed up hot.

I want one of those.

And if I'm in an area that has power issues, (in this heat where doesn't) I do my best to get a 3 phase voltage monitor on the unit.

Then again it could just be crap motors. Welcome to the Global Economy.

[allan38]

We've seen a lot of fractional HP motors that were not performing up to capacity.
They were not OEM but were aftermarket. The HP rating was the same, the amp rating was slightly smaller. They would overheat and go out on high limit. We went up to the next motor hp rating and made sure the amp rating was at least the original one and they worked fine. I think problem was the HP rating was approximate or the service factor was lower. Looks like many manufacturers are building as cheaply as possible instead of manufacturing it to a performance specification.

You can make the perfect motor and go bankrupt because you can't sell enough of them at a reasonable profit.. Make a good enough motor a little cheaper and stay in business.

[kaptnkirk]

We do Thermal Imaging also. They gave me the camera to do all the disconnects and contactors on the outdoor units and I couldnt focus due to the lighting..Thank god

[XcelTech]

When you are changing these motors are you changing the fan blades too?

Are you using a pulley pullers to take the blades off?

Are you making 100% positively sure that the blades are rotating in the correct direction?