# New motor draws overload current, old motor doesn't



## farlsincharge (Dec 31, 2010)

Reverse osmosis skid, backwash pump. 10 year old WEG 230/460 delta 7.5 hp motor has a noisy bearing. Decide to get a new motor, then rebuild the old one as a spare. 
Motor is OE and unavailable. Obtain new off the shelf US motor from nearest supplier, change end bell to c flange and install. Motor FLA is 20 amps, motor draws 30 amps and trips overload. Scratch head, and double check everything. No issues, should work.
Remove new motor and reinstall old one thinking pump issue caused during changeover?
Old motor hums away at 16 amps.
Decide there must be a mislabelled winding lead. Spend evening with light bulbs, batteries, and analog meters trying to confirm. Winding identification seems to check out.
Now at total loss, looking for insight, hat in hand.


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## micromind (Aug 11, 2007)

Since it's 7.5HP, it's most likely 9 leads. And at 20 amps, it's connected for 230 volts. 

The first thing I'd do is megger it, even though it's new. 

What is the no-load current?

Is the current roughly the same on all 3 phases? 

This can be done full-load or no-load; check the current on T1 and T7, they should be the same. Do the same on T2 and T8 then T3 and T9. 

Now look at the current on T1 and T4, they should be the same. Do the same on T2 and T5 then T3 and T6. 

If these currents are the same, the issue is not a mis-connection. It's something else. 

I'd also put the original end bell back on, I've never seen it but the C-face one could be machined wrong and if the rotor isn't centered in the stator, it'll draw excessive current, especially under load.


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## MDShunk (Jan 7, 2007)

Old one 1725rpm and new one 3650? Seen guys make that mistake about a million times. On pumping duty, that'll make the current draw go through the roof.


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## joebanana (Dec 21, 2010)

I have a feeling it's all on the nameplate. Try a bench test.
Table 430.250 states FLC for a 7.5hp @230v. is 22a.
You sure it's not single phasing? Maybe an eroded contact? Does the new one rotate freely? Does it have oil? I've seen "experienced" guys run newly installed motors without checking/filling the oil cup (oooops). Is your end bell square, torqued properly?


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## MechanicalDVR (Dec 29, 2007)

To follow up on MD's post, does the old motor have an rpm on the nameplate?

If it's an OEM motor it could also be a specific speed.


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## MDShunk (Jan 7, 2007)

MechanicalDVR said:


> To follow up on MD's post, does the old motor have an rpm on the nameplate?
> 
> If it's an OEM motor it could also be a specific speed.


True that. Whenever I see a Euro stye motor, like WEG, SEW, etc., I comb over that dataplate to see what (if anything) is weird about it. Probably solid advice on any motor, of course, but especially prudent on Euro motors.


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## MechanicalDVR (Dec 29, 2007)

MDShunk said:


> True that. Whenever I see a Euro stye motor, like WEG, SEW, etc., I comb over that dataplate to see what (if anything) is weird about it. Probably solid advice on any motor, of course, but especially prudent on Euro motors.


Learned through a bad experience.

Had a serious issue once with one (missing nameplate) that after a lot of calls and digging was 800 rpm.


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## MDShunk (Jan 7, 2007)

Missing dataplates.... grrr.

Where I'm at now, a lot of guys will whack the rivets out of a failed motor dataplate and carry it to the motor storeroom to hunt the new mtor. If that old motor is of a rebuildable size, it gets shipped out generally without that dataplate because the wrench still has it, ****canned it, or whatever. The inventory stores people will mark up a paper tag to put the rebuilt motor back in inventory when it comes back. When that motor gets reinstalled, it essentially has no dataplate now. Best of luck to the next guy replacing that motor. 

Short lesson.... don't chisel off dataplates. Don't screw the next guy.

Corrolary: What's up with these motor companies that make printed dataplates? Go to smear a little dirt off to read it better and you smear off the markings. Grrr. Laser etch or stamp it, for crying out loud.


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## MechanicalDVR (Dec 29, 2007)

MDShunk said:


> Missing dataplates.... grrr.
> 
> Where I'm at now, a lot of guys will whack the rivets out of a failed motor dataplate and carry it to the motor storeroom to hunt the new mtor. If that old motor is of a rebuildable size, it gets shipped out generally without that dataplate because the wrench still has it, ****canned it, or whatever. The inventory stores people will mark up a paper tag to put the rebuilt motor back in inventory when it comes back. When that motor gets reinstalled, it essentially has no dataplate now. Best of luck to the next guy replacing that motor.
> 
> ...


Exactly, pulling the plate off is just screwing everyone else, plain and simple.

I've also seen some of those printed tags shrink and melt when the motor overheats, there is nothing like a good old fashioned stamped metal plate.


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## Helmut (May 7, 2014)

MechanicalDVR said:


> Exactly, pulling the plate off is just screwing everyone else, plain and simple.


Some guys call that job security.

No different than guys who take panel schedules, so no-one else knows where anything goes.


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## MDShunk (Jan 7, 2007)

Helmut said:


> Some guys call that job security.
> 
> No different than guys who take panel schedules, so no-one else knows where anything goes.


In my case, I think it's just dimwits who can't remember horsepower, frame, and rpm long enough to walk to where new motors are stored. Some guys have declared to me "we don't have a new motor", when they're hunting something as simple as 1hp 56C motor (our most popular). I come to find out they're trying to match the exact catalog number. That's really nice, but hp, frame, and rpm is all I care about. Enclosure type sometimes too. I'll find something I can make go round-de-round, catalog number be damned.


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## MechanicalDVR (Dec 29, 2007)

Helmut said:


> Some guys call that job security.
> 
> No different than guys who take panel schedules, so no-one else knows where anything goes.


I guess that depends on the job and boss.

If I caught a guy working for me doing that he'd be leaving.


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## Bird dog (Oct 27, 2015)

Also bad is you can't do a quick check to see if the heaters are properly sized.


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## Helmut (May 7, 2014)

Would be curious is the motors are constant torque or speed?


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## QMED (Sep 14, 2016)

I just take a picture of the nameplate with my phone lol


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## MDShunk (Jan 7, 2007)

QMED said:


> I just take a picture of the nameplate with my phone lol


I wish I could do that. The place I'm at has a pretty strict camera policy. You could actually lose your job over something that simple. It's not my first experience with such a policy, but it does make things more inconvenient sometimes. Whatever they want to pay for. A note pad it is.


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## eddy current (Feb 28, 2009)

If there is no nameplate because it was removed, can you still legally install it? Up here it must have a CSA logo or it can not be installed


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## eddy current (Feb 28, 2009)

QMED said:


> I just take a picture of the nameplate with my phone lol


Or write down the info on a note pad. I always had paper and a pencil when working, seems to be a lost technique now a days


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## QMED (Sep 14, 2016)

Absolutely, everybody where I work carries pen, paper and a flashlight. If I brought my boss a chiseled off nameplate he would ask me why the hell I didn't just right it down lol.

For putting photos on our work computers we actually have to use a digital camera with a 3.5" floppy drive. It can store 10 pictures lol.


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## QMED (Sep 14, 2016)

eddy current said:


> Or write down the info on a note pad. I always had paper and a pencil when working, seems to be a lost technique now a days


Phone is a hundred times faster and I have a lot of walking to do if I mess up one of the numbers. Not to mention I take pictures of schematics on panel doors and many other things throughout the day. It's more efficient for me but my Rite-in-the-rain notepad is always in the shirt pocket. Yesterday we had a tech rep here and were working with a very busy schematic and it was difficult for 2 people to research in the same book at the same time. I snapped a few photos of the schematics and we were both able to research comfortably.


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## MDShunk (Jan 7, 2007)

eddy current said:


> If there is no nameplate because it was removed, can you still legally install it? Up here it must have a CSA logo or it can not be installed


Yes. ....


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## micromind (Aug 11, 2007)

MDShunk said:


> Old one 1725rpm and new one 3650? Seen guys make that mistake about a million times. On pumping duty, that'll make the current draw go through the roof.


That thought occurred to me sometime in the middle of last night.......but I was thinking the old motor could be 1140 and the new one 1750. 

Also, is it turning the right way?


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## John Valdes (May 17, 2007)

MDShunk said:


> True that. Whenever I see a Euro stye motor, like WEG, SEW, etc., I comb over that dataplate to see what (if anything) is weird about it. Probably solid advice on any motor, of course, but especially prudent on Euro motors.


LOL. Weg motors are manufactured in Brazil. They build NEMA and IEC motors. I visited that plant some years ago and was frankly very impressed. 
Here in the SE, Weg is the motor of choice for aggregate outfits. Weg is known for beefy, tough equipment in that industry.
Thy have a crusher duty line as well. 



MDShunk said:


> When that motor gets reinstalled, it essentially has no dataplate now. Best of luck to the next guy replacing that motor.
> Corrolary: What's up with these motor companies that make printed dataplates? Go to smear a little dirt off to read it better and you smear off the markings. Grrr. Laser etch or stamp it, for crying out loud.


You need to find a better motor shop. We always replaced missing and or damaged nameplates with metal plates. 
A good shop will be able to get everything on that nameplate. In many cases if you have the time, you can order a new nameplate.
But you need a good motor shop to get these type benefits.


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## MDShunk (Jan 7, 2007)

John Valdes said:


> You need to find a better motor shop. We always replaced missing and or damaged nameplates with metal plates.
> A good shop will be able to get everything on that nameplate. In many cases if you have the time, you can order a new nameplate.
> But you need a good motor shop to get these type benefits.


I guess if it was up to me, we might. I'm happy to report I have nothing in that decision. Quite often we send them out as one type of motor and they come back rewound as another type anyhow.


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## MDShunk (Jan 7, 2007)

John Valdes said:


> LOL. Weg motors are manufactured in Brazil. ...


They all look the same to me. I guess that makes me some kind of motor racist. :smile:


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## pudge565 (Dec 8, 2007)

MDShunk said:


> In my case, I think it's just dimwits who can't remember horsepower, frame, and rpm long enough to walk to where new motors are stored. Some guys have declared to me "we don't have a new motor", when they're hunting something as simple as 1hp 56C motor (our most popular). I come to find out they're trying to match the exact catalog number. That's really nice, but hp, frame, and rpm is all I care about. Enclosure type sometimes too. I'll find something I can make go round-de-round, catalog number be damned.


I have had cases of manufacturers changing catalog numbers for the exact same motor anyway. Like you said, 3 numbers I need and that is it...



MDShunk said:


> I wish I could do that. The place I'm at has a pretty strict camera policy. You could actually lose your job over something that simple. It's not my first experience with such a policy, but it does make things more inconvenient sometimes. Whatever they want to pay for. A note pad it is.


The pet food facility I worked at had a policy like that. We also had to use the metal detectable pens they provided which most times wouldn't write. It was kind of an unwritten rule that maintenance could use the phone for things like this. However if HR caught you no help from management so user beware...



eddy current said:


> If there is no nameplate because it was removed, can you still legally install it? Up here it must have a CSA logo or it can not be installed


Yes, there is no requirement in the NEC that all equipment be listed. The only time it is required to be listed is if it is specifically called out as such, motors are not.

That being said 430.7 has markings that are required such as manufacturer, rated volts and FLC, number of phases and frequency, etc. If if does not have this information it is technically not allowed to be installed.

With that being said, industry is kind of its own game in the states. You will most likely never find an industrial facility that has inspections after original construction.


On the topic of OEM motors, the very first job I had out of high school was in a medical waste destruction facility. We had a compactor hydraulic power unit that used an inverted shaft WEG motor. Came in one morning to the control panel and pecker head filled with oil. My boss didn't believe me when I suggested that the pump seal blew and pushed the oil through the pecker head up the LFNC into the panel. Replaced the pump and same thing happened 2 days later. Happened a few times. We came to find out that the OEM of the power unit changed suppliers for their hydraulic pumps and this was a known issue, it seems the new units couldn't handle the torque of the motor. OEM had no solution and since it was an inverted shaft we couldn't simply convert to couplings. The OEM was working on making a conversion unit to adapt the inverted shaft to a coupling type shaft instead of a C face. I never saw the outcome as I left before that happened.


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## farlsincharge (Dec 31, 2010)

The WEG motor is 3510 rpm, the US motor is 3525.

The first motor my supplier sent me was 1800 rpm, so this job has been a bit of a go round.


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## MDShunk (Jan 7, 2007)

farlsincharge said:


> The WEG motor is 3510 rpm, the US motor is 3525..


Then I'm out of ideas, unless your adapter flange somehow has the coupling area/motor bearings in a hell of a bind.


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## JRaef (Mar 23, 2009)

Yep, the difference in speed should only amount to about a 1% increase in current, so that’s not going to be it. I would triple check the connection pattern in the peckerhead, then if that’s absolutely correct, the only things I can think of are the bearing issue or possibly a bad winding on the new motor. It happens... I would jump out the OL only for long enough to be able to get individual phase current readings under that OL condition, make sure the high current is balanced. If it’s only on two legs, I’d be leaning toward a line-to-line insulation breakdown inside.


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## paulengr (Oct 8, 2017)

Is this startup only? IEC and re-rated as NEMA motors are notorious for excessively (NEC illegal) starting currents due to IEC “efficiency at any cost” requirements. I’ve seen them hit as high as 22-23x FLA which has lots of starting and protection issues. I know Toshiba and Siemens are notorious for this, not sure on WEG. I thought last I knew they weren’t that bad except for very cheap designs which are only semi-rebuildable for cast motors. The thin (high efficiency) rotor laminations are very fragile and tend to get destroyed if the bearing wipes out.


Sent from my iPhone using Tapatalk


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## Bird dog (Oct 27, 2015)

Have you checked the flux capacitor? :wink:

https://www.oreillyauto.com/flux-capacitor


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## MechanicalDVR (Dec 29, 2007)

Bird dog said:


> Have you checked the flux capacitor? :wink:


Or the wireless induction run modulating potential refractory isolater?


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## farlsincharge (Dec 31, 2010)

The windings have to either be mislabeled so the motor is fighting itself, or the rotor is off centre. Either way I guess I'm sending it back to the motor shop for a pm.


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## MechanicalDVR (Dec 29, 2007)

farlsincharge said:


> The windings have to either be mislabeled so the motor is fighting itself, or the rotor is off centre. Either way I guess I'm sending it back to the motor shop for a pm.


Sounds like a plan but did you ring out the windings?


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## just the cowboy (Sep 4, 2013)

*Dumb question*

I haven't heard this question asked yet. 
Is the new one 60 hz and the old one maybe 50 hz?
Can you get a tach on the motors and check old vs new RPM.


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## just the cowboy (Sep 4, 2013)

*Dumb question*

I haven't heard this question asked yet.
Is the new motor 60 hz and the old one maybe 50hz?
Can you get a tach reading on both old and new,


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## paulengr (Oct 8, 2017)

just the cowboy said:


> I haven't heard this question asked yet.
> Is the new motor 60 hz and the old one maybe 50hz?
> Can you get a tach reading on both old and new,




It’s 60 Hz from the nameplate speeds reported. A 50 Hz motor does not run slower. It’s just that instead of say name plate 2950 RPM it will be say 3450. The voltages and currents will be “off” too.


Sent from my iPhone using Tapatalk


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## Bird dog (Oct 27, 2015)

farlsincharge said:


> The windings have to either be mislabeled so the motor is fighting itself, or the rotor is off centre. Either way I guess I'm sending it back to the motor shop for a pm.


Have them get a new nameplate too.


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## sparkiez (Aug 1, 2015)

If the motors are very close in RPM, HP and FLA, the first thing that pops into my mind is that this motor is wired for the wrong voltage. It has been mentioned before, but I wanted to re-iterate this. I have seen it overlooked before.

The next likely thing is a mechanical bind. Perhaps the alignment is just a tad off. Can you run a temp 40A circuit to it so that you can take current draws on the windings and see if you have one side that is out of balance? That could lead you in the right direction as well.


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## micromind (Aug 11, 2007)

Long shot here but most 7.5 HP motors are 9 lead Y would stator. 

The 460 connection is the same for a Y and a ∆ but the 230 is different. 

If the stator is wound ∆ and connected Y, it'll cause problems........

East to tell.....if 7, 8 and 9 have continuity, it's a Y. If 1, 4 and 9 have continuity, it's a ∆.


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## Wiresmith (Feb 9, 2013)

farlsincharge said:


> The windings have to either be mislabeled so the motor is fighting itself, or the rotor is off centre. Either way I guess I'm sending it back to the motor shop for a pm.


identifying unmarked leads



DELTA







WYE


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