When General Electric came out in 1946 with the AKD breaker and switchgear line, it represented a shift forward to a newer emerging technology. Moving away from oil filled dash pots and breakers mounted to pieces of slate of various sizes and very little standardization of buss configuration, AKD switchgear and breakers were a much-needed step in the right direction.
Highlights of the product line include:
Standard frame sizes of 225, 600, 1600, 3000 and 4000 amps.
Individual poles mounted to a standard steel frame for each frame size.
Electro-mechanical type EC1 trip units which relied on spring tension to set up and adjust trip settings.
A mechanical levering in mechanism to aid the operator in installing and removing draw out elements from the cabinet.
Typical model numbers designated each frame size.
AK 1 15 for 225 amp
AK 1 25 for 600 amp
AK 1 50 for 1600 amp
AK 1 75 for 3000 amp
AK 1 100 for 4000 amp
The designation of 15, 25, 50, 75 and 100 indicates the breaker's potential ability to interrupt a fault in amps, for example and AK-1-50 is a 1600 amp maximum continuous amperage frame that would interrupt up to 50,000 amps in a fault. While the example, AK-1-50 was designed to run at a continuous 1600 amps load, often EC1 trip units would be installed with lower ratings and would allow engineers to derate individual breakers to say 600 amp and 800 amp, while still maintaining the 50Ka interrupt rating.
Dash numbers at the end of the model number indicate vintage changes which may change on board parts interchangeability but the breakers themselves, aside from the specific size of the EC1 trip units are all interchangeable. For example, an AK-1-25-1 may not look like an AK-1-25-9 but they are completely interchangeable if they have the same trip unit installed.
In 1955 General Electric made improvements to the product line but kept the newer breakers interchangeable with the older breakers.While still considered type AKD switchgear and breakers, the breakers themselves had a name change to AK-2-15, AK-2-25, AK-2-50 and so forth. Minor improvements came with the series overcurrent trip units which are now called EC2 and EC2A, but the major improvement was a spring charged mechanism which allowed for much faster opening and closing of the breakers and improved contact structures making them more reliable. The levering in mechanism also changed but while they might look different, they remained interchangeable with the older AK-1 series breakers. The other major technology improvement cam from the option of adding fuses to each individual pole which improved the interrupt ability of the breaker to 200,000 amps regardless of base frame size. The designation for these breakers added an "U" to the model number, such as AKU-2-25 and AKU-2-50. The switchgear for these fused breakers was specially made and while still considered type AKD breakers, they have no interchangeability with the older AK-1 style breakers. GEH-1830A Manual
In 1960, improvements and changes to the product line include AKD 5 switchgear around with breaker frames designated as AK-2A-25, AK-2A-50 and so forth. These are often confused by field technicians who miss the detailed model number and just refer to the breaker as an AK-25 or an AK-50. The best way to specifiy any of these breakers is in a series of photos which include a shot of the breaker overall, one of the trip unit and one of each nameplate (there are two on electrically operated breakers). Also, list any known extra accessories, for example, an undervoltage trip, a bell alarm or send photos showing them. GEK-7302 Manual
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