FAILURE OF MOTOR BY FLASHOVER IN STATOR

[BADVE]

IT IS OBSERVED THAT MOTOR HAS FAILED BY FLASH OVER IN THE STATOR. THE MOTOR WAS PROVIDED WITH TEMPERATURE SCANNER TO MONITOR & CONTROL THE WINDING TEMPERATURE. THIS PROTECTION COULD NOT WORKED. ANOTHER PROTECTION IS THROUGH MOTOR PROTECTION RELAY. HOWEVER THIS RELAY DO NOT COVER PHASE IMBALANCE & EARTH LEAKAGE PROTECTION. THE MOTOR IS ENERGY EFFICIENT TYPE. THE HELP IS EXPECTED TO FIND OUT THE CAUSE & TO AVOID THE RECURRENCE OF THE FAILURE.

 

[gce1991]

please give the rating and voltage details type of protection relay employed and the nature of industry cement/steel/mine/petrochemical

possible causes may be

1.Accumalation of conducting dust in the motor terminal boxes
2.loose termination in the terminals
3.sudden increase of mechanical load /Jamming of motor shaft
4.problem with supply voltage fluctuations

the exact reason has to analyzed if you provide more details as requested above

regards


eswaran
of th

 

[electricpete]

If the failure was by flashover (electrical breakdown in air or along surface), then winding temperature sensing would not be expected to provide any protection and is probably irrelevant.

So I'm not sure how the comments about motor protection relate:
Did you see evidence of thermal degradation of the winding?
Have you recorded abnormal winding temperatures?
Did any protective relay actuate? Which one? Do you suspect improper relay operatoin? Why?
On what basis do you identify this as a flashover? Did you observe the failed stator? Could you identify the point of failure on surface? If so please describe where on the coil it was?

 

[THooper]

Added info on common cause of motor failure:

In 1966 a consultant wrote: Contamination is probably the most common cause of motor failure, and claimed the single most common reason for bearing failure was contamination of bearing entrance of foreign material.

In 1974 IEEE completed an Industrial Plant survey and found that one-third of the motor failures were traceable to chemical, moisture, dust, and solvent attack, plus blockage of ventilation by such materials.

It is well known that 90% of motor failures today are due to four causes:
1. dirt
2. moisture
3. friction
4. vibration
The most common contaminants are:
* conductors, such as carbon duct
* hydrophyllic compounds, materials that absorb moisture from the air, such as salt.
* solvents
* corrosive chemicals, mostly acids and alkalis
and lets not foget about air borne dangers such as metal dust. This attacks in several ways, it is conducting and contribuites to winding breakdown by surface tracking. Second, it is abrasive, once deposited on windings, particles continually vibrate under the influence of the motor, eventually cutting their way through insulation.

 

[BADVE]

Mr.eswaran
of th
pl inform yr e mail id enable to send the photographs by mail of the damaged stator

regards
My email ID badveud@pnq.kpcl.co.in

 

[jbartos]

Suggestion to the original posting: Please, would you rephrase the description of the problem since the flashover is theoretically not possible to materialize in the motor stator since the conductors are insulated. According to IEEE Std 100 "Dictionary" the flashover takes place over some surfaces, surface impedances, or surface resistances that are between two exposed energized parts, for example high voltage tower ceramic or plastic isolators, surge arresters, cable terminations, and during high voltage testing.

 

[coolfish]

Could be referring to partial discharges (sparks) which could be mistaken for 'flashover'. Not aware of a protective device that will protect from such discharges. Generally protective devices will respond to other failures like grounds. But the partial discharges can be measured off line or on-line to get an idea of the condition of the windings and to predict failures.