Remedy for switching transients- 4160V motors
Remedy for switching transients- 4160V motors
(OP)
We suspect switching voltage transients have caused insulation failures in two 4160V motors and a cable. Motors are controlled by vacuum contactor starters.
More concrete data will have to be collected by further monitoring.
I would appreciate any input as to the remedies available to take care of the transients. Also has anyone run into similar situation? One remedy is to have the motor windings insulation of proper rating that I know.
We are contacting starter manufacturers to see if they have any recommendations.
More concrete data will have to be collected by further monitoring.
I would appreciate any input as to the remedies available to take care of the transients. Also has anyone run into similar situation? One remedy is to have the motor windings insulation of proper rating that I know.
We are contacting starter manufacturers to see if they have any recommendations.





RE: Remedy for switching transients- 4160V motors
Gunnar Englund
www.gke.org
RE: Remedy for switching transients- 4160V motors
RE: Remedy for switching transients- 4160V motors
VCB's, in theory, are supposed to produce what is called as voltage doubling depending on the time of closure / opening in a voltage cycle. A good winding insulation is supposed to withstand this.
* Anyone who goes to see a psychiatrist ought to have his head examined *
RE: Remedy for switching transients- 4160V motors
Edison: Some motors are very old (1960's) and some are new like 2 years old. One burnt is old. One new was assumed burnt.
It is interesting that new one is later found to be not burnt or damaged. Only its fuse (miscoordinated) appeared to have blown.The Owner assumed the motor had failed. The new starters were installed 2 years ago, I was stumped as to why the new motor, which supposedly should have proper insulation, will get affected by the transients.
At any rate I think this site still needs protection for the transients.
RE: Remedy for switching transients- 4160V motors
One of the factors used to justify removal of the surge caps was the cable length between starter and motor was long enough to provide enough capacitance to lower the rise time of any pulses to that defined by standards. The effect of motor feeder length needs to be considered when deciding if the problem is transients. In my case, about 70 m of cable was adequate.
If I didn't have a high resistance grounded system, I would have left the surge caps in because they did a better job of lowering the pulse rise time than cable capacitance.
RE: Remedy for switching transients- 4160V motors
Regards,
PowerfulStuff
RE: Remedy for switching transients- 4160V motors
NEMA MG-1 allows 2 surge levels: 2.0 p.u. and 3.5 p.u. If you don't specify anything, I think you are left with 2.0 p.u.. So it's better to specify 3.5. p.u. and also put coil and motor surge test requirements in your spec. Some users also add specific requirements for types of materials to be used in strand, turn, and ground insulation. EPRI has a pretty detailed spec in this regard.
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RE: Remedy for switching transients- 4160V motors
thread237-42676
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more." Nikola Tesla
Member, P3
RalphChristie (Electrical)
Interesting stuff to read:
ttp://www. electricit y-today.co m/et/issue 0401/i04_r efiner.htm ttp://www. joslynclar k.com/down loads/Vacu umTechnolo gyOverview withQA.pdf
rbulsara (Electrical)
(OP)
Thanks again. I had "refiner" article's copy, but was on hard drive and could not link it..thanks ralph.
jraef (Electrical)
More relevant info I recently came across for sharing. p://www.no japower.co m.au/techd oc/Docs/Th e%20Featur es%20of%20 0.4kV%20Mo tor%20Inte rruption%2 0by%20A%20 Vacuum%20C ontact.pdf
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RE: Remedy for switching transients- 4160V motors
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RE: Remedy for switching transients- 4160V motors
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