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EntelliGuard R Circuit Breaker Retrofill AKD-10 Installation Manual DEH41550 R06
History and Types
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 ANSI 61, 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—AK25/AK50
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 out 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.
Note: All legacy AK & AKR breakers have a draw out letter code “A”. EntelliGuard R retrofill breakers for this
gear will have a catalog number beginning with
R1
for AK replacements or
R2
for AKR-30/50 replacements.
AKD-6—AKR30H/AKR30L/AKR50H/AKRT50H
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 and will be
replaced by an EntelliGuard R with a catalog number beginning with
R2
. 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 which will be replaced by an EntelliGuard R
with a catalog # beginning with
R5
up to 2000A frame size and
R6
for 3200 & 4000A frame sizes.
