Will any OEM's test motors bolted down? 1

[electricpete]

Motor OEM's typically test small/integral-hp motors on resilient mount as allowed by NEMA MG-1.

Are there any OEM's that will test a motor (in particular 100HP frame 365TS 3600RPM ODP horizontal induction motor) bolted down to a rigid base and guarantee the NEMA required vibration for that configuration (0.12ips pk) or preferably the IEEE843 vibration (0.08ips pk)?

I'd be interested to hear which ones. I haven't had much luck finding any that have the facilities to do it.

 

[elecmec]

Vibration is a result of out of balance conditons. If the rotor is well balance, the vibration should be low. I once inspected motor generators (150HP) and our spec required a measurement in mil's of the vibraion in the x and y direction for each bearing. The set was mounted on a platform provided by the company. The origninal design base could not meet our spec, so it had to be redesigned to pass. Part of my inspection process was to examine assembly and testing during construction. Review records including balancing. All this required $$$ (can you tell this was a government job). In short, the motor and base as a system will determine the final vibration. Your spec and $$ will determine how much. Does this help?
Elecmec

 

[electricpete]

Thanks elecmec. The particular vib of my concern is 2*Line Frequency, which often increases when the casing is bolted down. One possible explanation is that the airgap is being distorted due to some small residual "soft foot". It is unrelated to mechanical imbalance, which manifests itslef at 1x running speed, IMHO.

 

[jbartos]

Suggestion: Try

http://www.iec.ch

IEC 60034-14 (1996-11) Ed. 2.0 Rotating electrical machines - Part 14: Mechanical vibration of certain machines with shaft heights 56 mm and higher - Measurement, evaluation and limits of vibration

 

[mbailey]

electricpete,

To your point, NEMA frame size through 447 are tested on a resilent base while 449 and larger are tested clamped down to a massive cast iron plate. This is primarily a need to meet a certain cycle time requirements during testing while maintaining good repeatibility and reproducibility in our testing methods. Special vibration testing, such as bolted down, is an option and can be requested at time of order. However, I do not recommend this option because more than likely, the motor base will not be nearly as massive as a production test plate. To address your 2xlf vibration, if this is present on a resilient base and a rigid base, check your connection for adjacent pole connection, particularily on slow speed motors. Changing the connection to alternating poles may be a solution.

 

[electricpete]

Can you provide some more details on the adjacent pole / alternating pole connection?

 

[jbartos]

Suggestion: Visit

http://www.flynnresearch.net/power_conversion.htm

for more info and patent

 

[jOmega]

jbartos:

FYI ... IEC not applicable to NEMA frame motors....

from electricpete's original post:

"Motor OEM's typically test small/integral-hp motors on resilient mount as allowed by NEMA MG-1.

Are there any OEM's that will test a motor (in particular 100HP frame 365TS 3600RPM ODP horizontal induction motor)"

The motor he referenced is a NEMA design, not IEC.

cheers

 

[jbartos]

Suggestion to the previous posting: I did not write that the IEC was an equivalent to NEMA, in this case.

 

[jOmega]

electricpete:

Rotors are balanced in a separate machine, prior to being inserted in the frame of the motor.

I can't speak for all OEM's and their mfg'g processes, but some that I know of do bolt down the motors at final test on a bed plate for final testing.

Advise if you would like further information and I will be happy to put you in touch with someone who has responsibility for test at a major motor OEM and is also a member of the NEMA committe for motors and generators.

 

[jbartos]

Suggestion: Visit

http://www.thomasregister.com

and type Vibration Analysis Services under Product or Service, which will return 160 companies to inquire about your particular motor test needs.

 

[electricpete]

Thanks for the responses. We found an OEM to do the test.

I remain of the firm conviction that customers are wise to specify their integral horsepower 2-pole motors to be tested on a rigid mount (rather than allowing supplier to choose either rigid or resilient allowed by NEMA). The rigid mount configuration is closer to installed configuration and 2*Line Frequency vibration can be considerably higher when rigidly mounted.

 

[jOmega]

jbartos:

Electricpete posted about a particular NEMA frame motor, and you posted:

jbartos (Electrical) Apr 19, 2002

Suggestion: Try

http://www.iec.ch

IEC 60034-14 (1996-11) Ed. 2.0 Rotating electrical machines - Part 14: Mechanical vibration of certain machines with shaft heights 56 mm and higher - Measurement, evaluation and limits of vibration

Kinda like someone asking about "growing conditions for Oranges", and he receives a reply about "Carrots"

Relevance ?

To paraphrase from Johnny Cochran's summation at the O.J. Simpson trial,:
"If the standard don't fit; you got to omit."



cheers

 

[jbartos]

Suggestion to the previous posting: Visit

http://www.iec.ch/cgi-bin/procgi.pl/

http://www/iecwww.p?wwwlang=E&wwwprog=cat-det.p&wartnum=021632

and notice that the standard deals with the motor speeds up to 3600RPM.

 

[jOmega]

I visited the site and am well familiar with the referenced IEC standard [IEC 60034-14 (1996-11)] .

Sorry jbartos, but the IEC spec your reference has no relevance or applicability to N E M A frame motors...
repeat: IEC not appropriate or applicable to N E M A Frame Motors.... which is the motor of this discussion thread.

As IEC is to Europe (in particular), NEMA is to the USA, and at this time, the twain do not meet. Motors in the USA are designed and manufactured to N E M A standards; not IEC. (Why do you think that is ?)

IEEE and IEC are presently working on evolving common standards; that is, standards that will be accepted in both Europe and the USA.

Maybe someday there will be commonality between IEC and NEMA.... but that day isn't now, and it isn't tomorrow.

I'm curious, do you think that bringing non-relevant references into a discussion adds clarity and meaningfulness?

Hmmmm.