Archive for the ‘General – Circuit Breakers’ Category


February 19th, 2010 Comments off

The term “breaker” as it applies to the electrical world usually means one thing, circuit breaker. The circuit breaker is designed to protect circuits. Contrary to what many believe, circuit breakers are not primarily designed to protect people from electric shock. That’s a subject for another article.


Breakers vary. They come in many sizes and types, ranging from the simplest molded case breaker to the most sophisticated types of breakers involving the newest current and voltage monitoring technology.


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Many people ask what part of the breaker is the most vulnerable to wear and tear. That is difficult to say because it depends so much on the environment and the type of use they are subjected to. In a poor environment for instance, (oily or dirty air) breaker mechanisms can become stiff, hampering the physical opening of the breaker. That’s why the exercising of the breaker during scheduled maintenance is so important. The importance of this cannot be overstated. 


Breaker contacts themselves, while designed to open under load conditions, often become pitted causing an increase in contact resistance over time.


A breaker failure can take many forms and can be the result of many things. When a breaker fails in service, it can often lead to expensive down time. MIDWEST is your best source to find a breaker replacement. Since 1977 we have helped many customers through breaker emergencies in short order. Call our expert engineering and breaker support team for your breaker needs. If you are looking for a new, used or reconditioned breaker, we are sure we have what you need.

High Current Testing Old Circuit Breakers at Low Voltage

October 20th, 2009 Comments off

MIDWEST was testing power circuit breakers for a large manufacturer.  The electrician working with us thought we were joking when we said we were putting 6000 amps through his 2000 amp main circuit breakers.  We told him to grab the bus from the test set to the breaker and he could feel the vibration and heat from 6000 amps.  He could hear the loud hum of the test set and the vibration of the old circuit breaker used in their foundry.  He wouldn’t touch it until we touched the bus first.  He had that strange look of “I see it, but I just don’t believe it.”  We told him the output of the high current test set was going into a direct short and the output voltage was only a couple volts.  We had him measure the output voltage with a voltmeter.  Then he understood what was happening.  It doesn’t take much voltage to push a lot of current through a dead short.