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Posts Tagged ‘square d’

Circuit Breakers: We’ve got what you need – All Manufacturer’s

February 23rd, 2015 No comments

Circuit Breakers: We’ve got what you need.  MIDWEST sells reconditioned, used and new Circuit Breakers.  Call today at 800.803.9256!   http://www.swgr.com/store/circuit-breakers/molded-case/home.aspx

All manufacturer’s available – Cutler Hammer, General Electric, ITE, Siemens, Square D, Westinghouse, ABB, Airpax, Allen Bradley, American, ASEA Brown Boveri, Bryat, Bulldog, Challenger, Crouse Hinds, Federal Pacific, Fuji, Gould, Heineman, Kraus Naimer, Merlin Gerin, Milbank, Mitsubishi, Moeller, Murray, National, Sace, Sylvania, Telmand, Thomas and Betts, Trumbull, Tyco, Vois Worth, Wadsworth, Zinsco, etc.

Image of Circuit Breaker Main and Arcing Contacts

July 9th, 2012 No comments

 

Circuit Breaker Main and Arcing Contacts with Copper Splatter

Circuit Breaker Main and Arcing Contacts with Copper Splatter

When discussing circuit breakers, we like to have good images to show the difference between the main contacts and the arcing contacts. When a circuit breaker opens, the main contacts should open partially first before the arcing contacts start to open. There should be no arcing damage to the main contacts because the arc interruption takes place between the arcing contacts. This protects the current carrying surfaces of the main contacts so there is minimum contact resistance at the main contacts. Good contact surface means no overheating. For the same reason, when the circuit breaker closes, the arcing contacts close first, suffering any arcing damage. After the arcing contacts are closed, the main contacts close. All this keeps the main contacts in good condition. The arcing contacts are enclosed in something called an arc chute that extends and separates the arc until it is extinguished when the circuit breaker opens. When the arc chutes are contaminated with dirt or high humidity or interrupt very high loads or fault currents, the arc chutes take a beating. Whether you’re talking about Square D circuit breakers, Cutler Hammer circuit breakers, Siemens, Westinghouse or GE General Electric circuit breakers, molded case circuit breakers, power circuit breakers, or medium voltage air circuit breakers, the function of the arc chutes is the same, take a beating to protect the main breakers. The attached image shows the damage to the stationary and movable arcing contacts and to the arc runner that extends into the arc chutes to extend and divide the arc until it is extinguished. The main contacts, the 16 curved segments across the middle of the image, are in good shape. No arcing damage what so ever. This image is from a medium voltage air circuit breaker.

Circuit Breaker Reset Tests

January 11th, 2012 No comments
1600 Amp General Electric Air Circuit Breaker - Catalog No. AK-2A-50-1

1600 Amp General Electric Air Circuit Breaker – Catalog No. AK-2A-50-1 Available at www.swgr.com

A customer called MIDWEST to ask why we did something called a “Reset Test” on his circuit breaker. He said he has had circuit breakers tested by switchgear service companies for nearly 30 years and never ever saw something called a circuit breaker “Reset Test.” He has Square D circuit breakers, Westinghouse circuit breakers, General Electrical circuit breakers and newer Cutler Hammer circuit breakers. He checked some of his old test reports and found no “reset tests.”  He had never used MIDWEST before, so he was pretty interested when we explained the reason and procedure for the reset test. The reason was a very pleasant surprise because it gave him greater confidence in the proper performance of his circuit breakers.  MIDWEST started using the circuit breaker “reset test” many years ago. It’s not a standard test procedure. You won’t find it in the text books or instruction manuals. You will find it in MIDWEST’s Training Manual under ‘Scars,’ meaning experience. It’s a carry over procedure from testing old dashpot type air circuit breakers and insulated case circuit breakers and molded case circuit breakers. The reason for the test is that occasionally, seldom but occasionally, a circuit breaker will nuisance trip when put back into service after it has been high current tested. For example, a 1600 amp air circuit breaker, after high current testing, might nuisance trip instantly at 500 amps.  Basically the over current device failed during the high current testing. This was far more common with older “non electronic” over current devices. New electronic over current devices are more reliable, but not perfect. Strange things happen. We are not talking about the service technician forgetting to put the settings back to the correct positions. We are talking about an actual defective device. The test only takes moments. In the interest of quality control, the reset test addresses the “consequences of failure” as opposed to the “probability of failure.”

Yes, we are paranoid about safety and quality.

Circuit Breaker Trash Barrel – Fried Load Terminal

February 28th, 2011 No comments
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 Broken Handle, Blasted Contacts

February 23rd, 2011 No comments

 

KD3400 Cutler Hammer Circuit Breaker For Sale

KD3400 Cutler Hammer Circuit Breaker For Sale

We grabbed another circuit breaker out of one of the junk breaker barrels. This one was a Cutler Hammer KD3400.  Again, at first the breaker looked clean and happy. But it only took a second to realize the operating handle was broken off. It takes a pretty hard blow to break the handle off a Cutler Hammer circuit breaker. Handles can be easily replaced. But further inspection revealed serious carbon residue in the area of the line side terminals. You could wipe it off but if there is enough to be visible on the outside, there is something seriously wrong inside. Most of the screws were still missing from the cover, so a technician had removed the cover for inspection of the interior of the circuit breaker and put the cover back on with only a couple screws. A quick conversation with the technician reveal that the arcing contacts were destroyed on two poles and two main contacts were seriously damaged. There was heat damage to pole pieces and arcing damage to the interior insulating, dielectric, material. This Cutler Hammer KD3400 circuit breaker was trash. The breaker did not need to be tested. It was rejected based solely on the visible damage to the operating mechanism, main contacts, and arcing contacts. Square D, Cutler Hammer, GE General Electric or Siemens circuit breakers, it doesn’t make a difference. When this happens, they all fit into the same junk barrels.

 

 

Circuit Breaker Infrared Scanning Disagreement – Lugs

October 27th, 2010 No comments

Infrared Scan of a Circuit BreakerWe read about a disagreement between two bloggers over whether or not infrared scanning, or thermography, was needed if you torque tightened the wire connections to power circuit breaker terminals during routine maintenance.  What occurred to MIDWEST were all the possible deficiencies we find in old, new, and replacement circuit breakers, using infrared scanning, that have nothing to do with whether or not the load terminals were tight.  One of the nasty deficiencies is when the cable lug in an old circuit breaker is very tight, but the lug is overheating because the screw, holding the lug to the breaker output tab, is loose. We’ve seen brand new circuit breakers and replacement circuit breakers fry the load side tab of the breaker so bad that the breaker had to be replaced. This is true for new or old Square D, GE General Electric, Westinghouse, Siemens, Cutler Hammer, ABB, any manufacturer. It has nothing to do with a specific circuit breaker manufacturer.

 

Sometimes the lug is welded to the tab from the arcing between the lug and tab. There is a very sophisticated test one can perform during a maintenance outage to check for this defect. First, check for voltage at the load and line side of the de-energized circuit breakers. Don’t care that the main breaker is off and all the feeder breakers are open.  Check voltage anyway.  You are checking for something that shouldn’t be, not for something you know should be.  We, rather I, have personal experience with getting my hand blasted because a breaker was back fed. Very bizarre set up, unbelievable, just waiting to injure someone.

 

After checking for voltage, carefully and gently try to move the conductor coming out of each phase of each circuit breaker.  You are trying to see if the cable is loose in the lug and you are trying to see if the lug is loose, moves or turns, in the circuit breaker. You are not trying to force it to move. Just use enough force to see if it is loose in the circuit breaker. If the lug itself is loose, the cable or cables will need to be removed from the lug; The mounting screw for the lug properly tightened; The cables properly reinstalled; And the cables tightened in the lug. Again, don’t be too forceful. On small breakers, you can always make the lug move. Repeating, you just want to use enough force to see if the lugs for that old obsolete circuit breaker are loose.

 

If the conductive interface, between the lug and the circuit breaker, is damaged from severe overheating or arcing, the defective circuit breaker may need to be replaced. Sometimes the damaged area can be repaired.  MIDWEST does not recommend replacing power circuit breakers while the switchboard is energized. Be safe. Turn things off. Check for voltage everywhere.

Square D I-Line Molded Case Breakers

April 9th, 2010 No comments

What is it about these breakers that people like so much? In a word, simplicity ─ they are quick and easy to work with.

 

Most breakers such as the Cutler Hammer EHD3100, to give one example, use “details” (mounting bus details) to attach the breaker line side to the panel board bus. Details are an additional item at a slightly greater expense and are not necessary for Square D I-Line breakers.  I-Line breakers line side connections are finger clusters which connect directly onto the panel board bus making swapping out an I-line breaker as easy as drinking a cup of coffee in the morning.

 

The process is pretty straight forward:

 

First up, de-energize the panel board and lock out and tag out the switch supplying power to the panel board. Check voltage to make sure the panel board is dead and that it is not being back fed through another source. Remove the panel board dead front. Loosen the load side lugs and remove the load side cables from the breaker. You now have access to the single mounting screw holding the I-Line breaker in place. After removing the mounting screw, place a screw driver in the prying slot on the mounting bracket on the load side of the breaker and pry the breaker horizontally away from the bus running vertically down the center of the panel board. The breaker can now be removed from the panel board. Put the new I-Line breaker in place and using a reverse prying motion, slide the breaker horizontally into position such that the line side finger clusters make complete contact with the bus. Insert the mounting screw and tighten firmly. Do not over tighten this screw as it is a sheet metal screw designed to hold the breaker in position only. Reconnect the load side cables, then go ahead and install the dead front back onto the panel board.

 

At this point it’s always a good idea to exercise the breakers in the panel board, working the action by opening and closing the breakers several times. With the breakers in the off position in the panel board you are now set to power back up.