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Posts Tagged ‘Trip Device’

Circuit Breaker Trash Barrel – Fried Load Terminal

February 28th, 2011 Comments off
Blog Barrel of Scrap Breakers

Blog Barrel of Scrap Breakers

This is another circuit breaker trash barrel blog. I went to one of the many barrels of trashed circuit breakers and grabbed a breaker out of one of the barrels. We thought these barrels of discarded breakers would be a gold mine for useful circuit breaker maintenance, testing, and reconditioning blog information. So today’s blog is about a Cutler Hammer ED3200, style number 6610C75G04, 200 amp molded case circuit breaker. The breaker looks great. Looks like it was cleaned up but then thrown out. It was. But the operating mechanism was defective.  It would not latch and it would not close the circuit breaker. The cover had indications of overheating at the center pole of the load side of the circuit breaker. There was a piece of the copper conductor still in the load side center pole terminal. The feeder had been cut off rather than remove. The strands of the conductor and the lug were fried. That’s a technical term for overheated to the point of brown discoloration, corrosive appearance on the surface of the lug and on the set screw holding the conductor in place. The metal tab under the lug surface was brown from overheating. The top view showed the top of the lug set screw was also burned and brown. We know from experience that the lug can’t be removed without damaging the load side center pole tab of this Cutler Hammer ED3200 200 amp circuit breaker. We know the heat has damaged the trip device and dried out the interior operating mechanism. A breaker damaged like this, whether a Square D, GE General Electric, Siemens or Westinghouse circuit breaker, is junk and needs to be destroyed. So into the scrap barrel it goes. Warning, one might ‘fool around’ with this breaker and get the operating mechanism to function and maybe finally get the old piece of cable out, but the breaker is still junk. Put it on the table, come back in a week and I’ll bet you it doesn’t work again. If you removed the cover, you would instantly see why.

 

Circuit Breaker Trip Device – Hidden Defect

February 2nd, 2011 Comments off
 
Square D PAL362000 Circuit Breakers For Sale

Square D PAL362000 Circuit Breakers For Sale

MIDWEST asked our Switchgear Engineering Technicians for an example of a molded case circuit breaker that had a hidden defect that could only be found by experienced testing.  We find many used circuit breakers that have defects that can be found by a close visual inspection.  Sometimes the defect may not be obvious but an experienced Engineering Technician knows where to look and would find the problem. In the business of repairing and reconditioning circuit breakers, we find about every possible problem that can occur. Whether we are reconditioning a replacement Westinghouse, General Electric or Siemens circuit breaker, many of the problems are the same. But we also frequently find hidden defects that could only be detected using proper testing.

 

 

For this example, let’s just use a replacement Square D PAL362000 circuit breaker. The breaker was reconditioned, which involved removing the cover to thoroughly inspect and maintain the interior of the Square D circuit breaker. The technician was immediately suspicious because he detected the slight smell of an overheated circuit breaker. Once you get that smell in your nose, you never forget it in the future. Even a small whiff tells you there may be a problem. In this case everything visible was in very good condition. There were no signs of overheating at the contacts or the line or load side breaker terminals. But the contact resistance test results indicated very high resistance on the center pole. A DLRO, digital low resistance ohmmeter, was used to locate the problem. The usual location is either the contacts, the bolted connections to the trip device, or the line or load side terminals or lugs. In this case the defect was inside the trip device. And a close sniff of the trip element confirmed it. MIDWEST performed an additional test, a high current test, to determine the voltage drop and therefore the resistance in the trip device on the center pole. Even though this replacement Square D circuit breaker looked just great, the trip device was defect and had to be replaced.