Type 50-DH-50 Air Circuit Breaker
The 50-DH-50 Air Circuit Breakers are designed
for indoor operating service at a-c voltages of from
2200 to 5000, for normal current loads up to and
including 1200 amperes and for an interrupting
duty of 50,000
KV
A at 25 and 60 cycle frequency.
They may be used on indoor applications where an
air circuit breaker is desired. They are character
ized by long life and moderate maintenance require
ments when operated under severe duty.
DESCRIPTION
General
Figure 1, Page 3, shows a 600 ampere 5000
volt, type 50-DH-50, 3-pole circuit breaker
equipped with a type SAF-2 operating mechanism
as developed for metal clad switchgear use. The
breaker consists essentially of a back mounting
plate on which are mounted three individual pole
units, each with its own contacts, arcing chamber
and magnetic circuit. The three contacts are oper
ated through pull rods, shaft and a connecting link
by a single electric solenoid which is trip free in all
positions. Figure 2, page 3, shows a side view of
the same breaker with one arc chamber and the
inter-phase barrier removed.
Figure 3 shows a drawing of the breaker locat
ing the various parts,-the primary disconnecting
contacts are shown by Figure 4, page 5. The
operating mechanism with auxiliary switches and
BARRIER
all low voltage control accessories are located
below the high voltage parts and isolated from them
by a horizontal steel barrier to which a vertical
plate is attached. This vertical plate supports the
bushings, contacts, magnetic circuits, and arc
chambers, all of these parts being at high potential.
Operating Mechanism
The electrical operating mechanism supplied with
this breaker is the direct current solenoid type
SAF-2 slightly modified to be adaptable to the ap
plication involved. This mechanism is mounted so
that the moving core, operating in a vertical plane,
acts through a toggle linkage, connecting rod, ro
tating shaft, and pull rods to close the breaker
contacts. After a normal closure, upon de-energiz
ing the closing coil, the moving core is returned to
its normal open position by gravity; the breaker
being held closed by the mechanism linkage until
tripped by one of the tripping devices which form a
part of the mechanism. If specified, a cut-off
switch, to energize a control relay for interruption
of the closing coil current, will be supplied. The
latch-checking switch, when required, is mounted
on the upper left side of the mechanism and is
operated by the mechanism tripping latch. An
auxiliary switch with a maximum of ten contacts
is mounted vertically on the right side of the mech
anism. This switch is operated simultaneously with
the circuit breaker contacts.
TWO LIFTING HO LES
Pi
DIA
l
FRONT
AI'CING
HORN
LEVERING
·IN
DEVIOE
AUXILIARY
SWITCH
TRIP ATTACHMENTS
NAMEPLATE
TO
SHUN�
STRAP
B �
FINGERS
�
GROUND
CONTACT
ACCEU:RATING
SPRING
S ECONDARY
CONTACTS
SLIDE
CASTOR
Fig. 3-Type 50-DH-50, "De-ion"
Air
Circuit Breaker, Front and Side View
4
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