History and Types
10 - History of AKD
AK - Power Circuit Breaker Equipment
D - Drawout circuit breaker construction
Manufactured from 1951 to 1975, all bolted, copper bus design, all drawout breakers AK-1,2,
3,-15 / 25 / 50 / 75 / 100; the 4000A-max bus rating. Breakers had a ratcheting drawout
mechanism, with an open-door drawout. Breakers were painted ANSI61, light gray,
manufactured in Philadelphia from 1951 to the mid-60s and in Burlington, Iowa from the
mid-60s to 1975.
The breaker compartment was a welded assembly, and the equipment frame was bolted.
Breaker boxes were stacked to make a vertical section with equipment frame around the
breaker boxes. There were no bus compartment barriers, just an open bus design. Ring
silver-plating was applied to bolted connections.
AKD - 5
Manufactured from 1960 until 1977, the aluminum bus had copper that was “flash-butt
welded” to the aluminum at bolted connections. During that time, AK-2A, 3A -25 / 50 / T50 /
75 / 100 (“A” signifies AKD-5 drawout) were produced. Breakers up to 2000A had primary
finger clusters. 3000 & 4000A breakers had a circular primary finger cluster arrangement in
the switchgear compartment. Pull-lanyard drawout mechanism in the switchgear on early
designs was replaced by a single jackscrew mechanism and then later replaced by a double
jack-screw mechanism. Featured is a closed-door, drawout with inner house breaker
compartment, where door moves with the breaker as it is racked in or out. Two bus levels
are available with a ring bus used at 4000A. Particulars include: welded/riveted frame, bus
compartment barriers, line/load separation barriers on mains and ties, isolation barriers on
transformer transitions, copper runbacks on feeder breakers, ring silver-plating on copper,
and aluminum bus un-plated (welded connections). The switchgear is painted sand-gray
(beige), with some instrument doors painted blue. AKR-30/50 in 22"-wide sections were
introduced in AKD-5 construction, early 70s. AK25s and AK50s were also available as
substructure kits for OEMs to build around customer gear.
None of the Emax 2 Retrofill breakers utilize fans except for 3000A rating only.
Note: All legacy AK & AKR breakers have a draw out letter code “A”.
AKD-6 was manufactured in Salisbury, NC from 1977 to 1981. Some AKD-5s, which were built
in Salisbury from 1975 until 1977, got name-plated as AKD-6. There is no “flash-butt” welded
aluminum to copper. Aluminum bus is tin-plated and bolted at shipping splits (but welded
everywhere else). Copper bus design has ring silver plating at bolted joints. AKR-75 / 100s
were introduced during this time. Stab-and-finger connections on 3200A and 4000A breakers
were improvements, versus the round the primary disconnects on the AKD-5. The 4000A
breaker was also narrowed to same width and phase-phase spacing as the 3200A.
The AKD-6 uses inner-house drawout breaker compartments on the 800 - 2000A breaker
compartments. They are painted ANSI 61 light gray and breakers have ECS or SST trip units.
AKD-6 should mark a shift away from all AK breakers and to AKR breakers. The AKR-30/50/
50H/T50 breakers used in AKD6 have a shallow 1” steel front escutcheon are drawout letter
code “A” i.e. AKR-4A-30. The AKR-30/50/50H/T50/75/100 breakers sold to OEMs for their
switchgear have a 5” deep plastic front escutcheon & spring loaded sliding “picture frame”.
These are draw out letter code “B” i.e. AKR-4B-30.The AKR-75/100 breakers used in AKD-6 have
a shallow 1” steel front escutcheon and vertical primary fingers. They are drawout letter code
”C” i.e. AKR-4C-75.
None of the Emax 2 Retrofill breakers utilize fans except for 4000A rating only.
AKD - 6
©2022 Emax 2 Retrofill Circuit Breakers 800A-4000A 9
2TSA451014P0000 Rev-B
