Motor nameplates - attached by? 3

[pmover]

bear in mind that i'm not a sparky, but a gearhead; so bear with the me a little on this question . . .

an analogy, when pressure vessels are designed, constructed, and tested by a fabricator, the fabricator attaches a nameplate to the pressure vessel stating the design and tested conditions of that particular vessel. any repair done to the vessel require that the repair stamp be attached to the vessel as well.

i know of a situation where the motor nameplates were attached by the contractor at the jobsite for electric motors > 250 hp, 4160 V. not only that, the data on data sheets from reputable motor mfg company contain inconsistent data (i.e. motor amp data for a larger HP motor, but a lower HP rating is stamped on nameplate). Not only that, there are identical units with these motors and these motors are physically different (new motors), yet same frame number.

so this leads me to ask the question of the electrical guys. Motor nameplates - whom (mfg, contractor, etc.) is to attach the motor nameplate to an electric motor and when is the nameplate affixed to the motor? Where in the electrical codes/stds can I search or obtain information regarding affixing/attaching motor nameplates?

It seems to me that since a motor mfg is fabricating and testing a motor, the mfg, not contractor, is to affix/attach the motor nameplate.

I hope this matter is explained well enough without getting too in depth with the details.

Thanks!

-pmover

 

[waross]

It depends on the contractors qualifications. In some jurisdictions, an accredited motor rewind shop can legally change nameplates.
Look in the motor section of the NEC.
Find a dimension chart (I like the Baldor Motor site.) and check the frame size. However inconvenient and misleading it may be, to have the wrong frame size shown, I don't believe that the frame size is required by code to be shown on the nameplate.
yours

 

[pmover]

these motors are for a new installation (i.e. new motors!). no motor rewind shop is involved. i really do not care about frame size other than the one motor is physically different than the others at the site.

motor section in NEC does not address/answer my questions. nec merely states what the nameplate should have on it, not whom is authorized to attached nameplates to newly fabricated motors.

your posting has me thinking . . . what if these motors are re-furbished or re-wound, i suppose then an accredited motor re-wind shop can legally change the nameplates.

-pmover

 

[electricpete]

The biggest question I have is: Why were the nameplates being attached/reattached after delivery? Ask the people who did it? I'm sure they didn't do it because they were bored. There must have been some unusual circumstance that led them to this practice.

I don't know of any standard, other than NEMA MG-1 which gives requirements for what needs to be on the nameplate. It is reasonable to assume that the manufacturer that you buy the motor from per that spec (MG1) is responsible to apply the nameplate before delivery.

As a user facility we have in limited circumstances made annotations on/near the nameplate if we found it in error (bearing number).

For rewind and refurbish, typically the information on the nameplate is not substantially changed. (horsepower and speed and bearings and code class etc rarely change unless there is a major rerate/modification). Insulation class may change. Whether or not this type of info is recorded on the outside of the motor is a matter between the repair shop and the user... may be required by some user specs and may be standard practice for some shops. (to record dates of rewind/refurb with limited additional info). Either way it is generally an additional nameplate added near the original and does not involve removing the original nameplate.

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[jraef]

I think it is important to understand motor power as well. HP (or kW as the case may be) is just a simplified method of describing a minimum amount of torque being available at a given speed. There is nothing preventing a motor from being rated for LESS than what it was designed for (other than the fact that overall efficiency is reduced relative to what it might have been at the higher rating). So if, for instance, you have a 5HP load, but the ambient temperature is extremely high, you could simply relable a 7.5 or 10HP motor for 5HP. If you then select the Overload Relay to protect it as a 5HP motor, the higher ambient will not have as much detrimental effect on the motor life. If you don't relabel it, someone might later assume they can use it at 10HP and change the protection devices, which would allow the motor to overheat.

This was done a lot in the past with motors used on inverter applications as a way of dealing with the lowwer cooling capability of the motor at low speeds. Now however, motors specifically designed for inverter use are a better idea for a host of other reasons not germain to this thread.

So, you may in fact see motor nameplates changed DOWN from their original design, there is nothing inherently wrong with that. UP from their original design is an entirely different matter however.

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[pmover]

remember, a gearhead is responding . . .

electricpete,

i wholeheartedly agree with the question of why were nameplates changed after delivery, but there is a high level of dis-trust, satisfaction, inconsistencies, etc. with this contractor. hence, the search for electrical codes/stds (IF ANY EXIST) that motor mfg's or otherwise are required to affix/attach to motors after some QA/QC work/testing is accomplished (i.e. similar to what the pressure vessel fabricators are required by law to accomplish).

jraef,

thanks and i understand "nothing preventing a motor from being rated for LESS than what it was designed for" & "you may in fact see motor nameplates changed DOWN from their original design, there is nothing inherently wrong with that". however, in this case, ambient temp is not a factor for de-rating the motors and elevation is << 1,000 ft.

it seems rather strange/odd to furnish motor data sheets stating a higher HP, but nameplating the motor for some smaller HP rating (i.e. install a 400-HP, 4160V motor and attach a nameplate stating a 300-HP, 4160V motor).

thanks fellas, i still do not quite understand, but such is the life of a gearhead i suppose . . .

-pmover

 

[dpc]

I suspect UL has some requirements for motor nameplate data, along with NEMA, but this is not really a legal requirement - it's not the same as pressure vessel requirements.

 

[jraef]

I didn't mean to imply that ambient was the only reason to derate. I just meant to explain that derating happens based on something that someone knows about the application. Lowering the nameplate rating is a way of ensuring that at some future date when the original intent was lost, abuse of the motor is less likely. Combined with dpc's statement you can see that this is something that happens quite often. In fact, the irresponsible position would be to know that 400HP 4160V motor must be treated as if it were a 300HP, but not do anything about it.

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[macmil]

I note your relationship with the contractor; an unsatisfactory state of affairs. Points that cause me concern are
1) are you saying that the physical dimensions of the motor in question are different from the other "identical" motors ? Frame sizes are factual from the motor manufacturer and can be checked. Bearings, shaft size, bolting dimension differences from expected could be embarrassing ( read costly ) during a shutdown / failure. What does the motor manufacturer say about this ?
2) you don't say what the driven equipment is, but if the actual motor torque is greater than design, the driven equipment may be subject to increased stress during starts leading to premature failure of gear reducers etc.
3) Presumably the specs didn't call for identical motors, opening the door for use of an oddball motor.
If you haven't paid all the money, you may be able to get a fuller explanation !! I hope you can get it.

 

[pmover]

dpc,

thanks for the response! i suppose you get a star as does jraef!

jraef,

yes, i understand what you meant and the de-rating of electric motors. my response was merely for clarification purposes . . . sorry for the alarm bell . . .

also, your last statement IS valid as there is concern about the as-built data/dwgs, which indicate the smaller HP motor. ALSO, there is the possibility of VFDs being installed in the future. so that means the VFD mfg and associated electrical gear needs to be sized for ACTUAL motor HP, not what is nameplated on the motor.

thanks fellas!

-pmover

 

[LionelHutz]

What certification is on the motors? If these are UL listed motors then UL rules say that the nameplate, which indicated it's a UL approved motor, must be applied at the factory. If it is not applied at the factory then a UL representative must acompany the person who is affixing the rating plate in the field. I'm sure there are similar rules for other approval agencies. If they're doing this stuff in the field then UL might pull their listing if they hear about this happening a few times. But then, they might also do nothing.

To me, it sounds like they just de-rated a few motors so that what they sold you appears to be exactly what you wanted. They are likely afraid that if they supply a 400hp motor where you ordered a 300hp motor then they may have to change it out to be a 300hp motor like you ordered.

 

[waross]

I would guess that someone had some 400 hp motors in stock that they were stuck with and sold them to your contractor cheap. If so, then your starting current will be greater and a 300 horsepower starter will not be adequate to interupt the current if the motor is overloaded and actually putting out 400 or more hoprsepower.
The power factor will be lower.
If the motors are 400 hp motors the contractor possibly changed the nameplates rather than instal the more expensive switchgear, starter, and circuit conductors for a 400 hp motor.
I would call the motor manufacturer for advice. You may get some information from the manufacturers website as to whether they have ever built a 300 hp motor in that frame size. The electrical inspecter may be your friend if he is not already the friend of the contractor.
respectfully
You may also have a case against the contractor on the basis of efficiency if the 300 hp motors are shown with 400 hp current ratings. with the

 

[jraef]

The electrical inspecter may be your friend if he is not already the friend of the contractor

LOL

No disrespect waross, I know there are great inspectors out there, but I doubt you could find a contactor who would want one to marry his daughter!

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[pmover]

LionelHutz,

these motors are UL listed and thanks for the clarification and information. also, technical information obtained from mfg website DOES substantiate that the installed motors are the larger HP AND the lower HP motor is available in same frame size.

waross,

thanks for the information.
also, in agreeing with jraef, when qa/qc program is accomplished by same contractor, little enforcement or oversight is conducted; hence problems will occur. regardless, your point is understood and demonstrates a fallacy with qa/qc programs.

thanks again fellas!

-pmover