History And Types; Akd; Akd-5-Ak25/Ak50 - ABB EntelliGuard AKD-5 Installation Manual

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
The 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 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 breakers sold to OEMs for their switchgear have a 5" deep plastic front escutcheon &
9 EntelliGuard R Circuit Breaker Retrofill AKD-5 Installation Manual DEH-41547