×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

reasons of flash in air break contactor of 3.3kV motor

reasons of flash in air break contactor of 3.3kV motor

reasons of flash in air break contactor of 3.3kV motor

(OP)
hi dear all,

we had a blast in a 3.3kV air breaker contactor connected to motor of same ratings, the flash blast occured the moment we tried to close the switch, after a period of long time. But first, we opeated the above mentioned contactor, by giving it 3.3kV supply on NO LOAD and it operated fine, but when we connected motor (load), flash occurs, kindly suggest possible reasons thanks.

RE: reasons of flash in air break contactor of 3.3kV motor

What do you mean by "flash"? Whenever you make contacts in air and a load is connected down stream, you will see a brief flash as the arc jumps the gap when the dielectric properties of the air gap become lower than the potential across the gap. It is even worse when breaking a set of contacts. It's for that reason that many people no longer use air break contactors on medium voltage motor applications, choosing instead to go with vacuum contactr technology. If you don't like the flash, change it out with a vacuum contactor.

But another VERY disturbing aspect of this is that you saw the flash. I hope for your sake it was seen through air vent openings in the enclosure, not because you operated an air break contactor with the door open!

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)

For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies

RE: reasons of flash in air break contactor of 3.3kV motor

jraef,

You are correct. It is hard to imagine being able to see the normal flash of an air break contactor unless the door is opened and the arc chute is removed. Like you, I hope he wasn't operating the starter like this. That is a recipe for disaster!

The OP did use the words "blast" and "flash" interchangeably. For a "blast", the implication is that there is a fault in the motor feeder cables or in the motor itself. Even in this case, it is hard to imagine being able to see the "flash" that accompanied the "blast" if the door was closed and the arc chutes were installed. That is, of course, unless the door was blown open by the fault. surprise

I don't think we can come to any good conclusion without more information from the OP clarifying whether this was a "flash" or "blast", whether any fuses were blown or overloads tripped, and what damage, if any, resulted to the contactor from this event.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources