History And Types; Akd; Akd-5-Ak-25, Ak-50, Akt-50, Ak-75, Ak-100 - ABB AKD-5 Installation Manual

Figure 5. AKD-6 - Retrofill Cassette Assembly (Rear
View)
The EntelliGuard R Circuit Breaker is suitable for application on power systems up to 635 VAC 50/60 Hz.

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; with a 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—AK-25, AK-50, AKT-50, AK-75, AK-100
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.
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.
8 EntelliGuard R Circuit Breaker Retrofill AKD-5/6 Installation Manual
Figure 6. AKD-6 - Retrofill Cassette Assembly (Front
View)
LOADING RAILS
LOCKING LATCH
BOTH SIDES
DEH0005240 R01