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.
MIDWEST Uncategorized air circuit breakers, circuit breaker, Cutler Hammer, GE, general electric, High Current Test, Insulated Case Breaker, molded case circuit breakers, Nuisance Trip, Over Current Device, Reset Test, square d, Westinghouse
In MIDWEST’s training classes for qualified personnel, there is a segment where we explain the long time delay range within which a Square D 1000 amp circuit breaker should trip due to an overload. This information is received with anything from amazement to skepticism to outright disbelief, even though we show the Square D circuit breaker characteristic trip curve. The overload time delay information is not restricted to Square D circuit breakers. It’s the same with Cutler Hammer, GE General Electric, Siemens, ITE, Westinghouse, Merlin Gerin, or Federal Pacific circuit breakers.
In our training example we use an old Square D 1000 amp MA type circuit breaker. If we tested this circuit breaker at 3000 amps, that’s 300%, the minimum to maximum trip range is about 45 seconds to 340 seconds. It might trip in 45 seconds or it might not trip for 340 seconds. This is an old thermo-magnetic circuit breaker, which typically works by heating a bi-metal in the over current trip device. Many newer breakers use electronic over current devices which have more repeatable overload time delay test results.
The illusion is that these Square D, Cutler Hammer, Westinghouse circuit breakers are designed to directly protect people. They are not. The breakers protect the equipment connected to them and they protect the electrical system. They are designed for the characteristics of the equipment connected, such that connected equipment will not be damaged by an overload or fault. This is a basic limited explanation. So, when you think of molded case circuit breakers, power circuit breakers or air circuit breakers, it’s important to know these breakers don’t just trip right at the breaker trip device rating.
MIDWEST Uncategorized air circuit breakers, breaker trip device, circuit breaker, Cutler Hammer Circuit Breakers, Electrical Safety Training Class, Federal Pacific Circuit Breakers, GE Circuit Breakers, General Electric Breakers, ITE Circuit Breakers, Large Over Current Time Delays, Merlin Gerin Circuit Breakers, molded case circuit breakers, Over Current Time Delays, over current trip device, power circuit breakers, Siemens Breakers, Square D Circuit Breakers, thermo-magnetic circuit breaker, westinghouse breakers
