25
Instruction manual
| Types SDV-R and SDV-R-AR distribution circuit breakers
The circuit breaker vacuum interrupter fixed
contacts are bolted to the upper fixed-end
pole heads while the moving contact ends
of the vacuum interrupters are attached to
the connector box. The same connector box
is attached to the ground switch vacuum
interrupter moving contact ends with the
fixed-end pole heads connected to the fixed
contact ends of the interrupters. This
arrangement stabilizes both interrupters
against lateral forces via centering rings on
the connector box. The external forces due
to switching operations and the contact
pressure are absorbed by the insulated
struts.
The primary current-path assembly consists
of the circuit breaker fixed-end pole head,
the stationary contact, and the moving
contact, plus the flexible connector between
the moving contact terminal clamp and the
moving-end connection pad. For the
grounding path, the assembly contains the
circuit breaker moving-end connection pad,
the flexible connector and the interrupter
moving-contact, the stationary contact and
the ground switch fixed-end pole head.
Vacuum interrupter (Figure 10: Vacuum
interrupter cutaway view on page 24)
The moving-contact motion is aligned and
stabilized by a guide bushing. The metal
bellows follows the travel of the contact and
seals the vacuum interrupter against the
surrounding atmosphere.
Switching operation (Figure 11: Vacuum
circuit breaker operator module on page
24, Figure 12: Stored-energy operating
mechanism shown in OPEN position on
page 26, Figure 13: Mechanical linkage
on page 27)
The vacuum interrupters moving contacts
are operated by angled levers fixed to the
main drive shafts via insulating switching
rods and levers. Contact pressure springs are
connected directly under the moving
contacts. The circuit breaker and ground
switch vacuum interrupter movable contacts
are connected and move in the same
direction. This configuration operates in
such a way that as the circuit breaker closes,
after a close command is initiated, the
ground switch opens at the same time; or
vice versa when an open command is
initiated.
Stored-energy operating mechanism
The stored-energy operating mechanism of
the operator is an integrated arrangement
of springs, coils and mechanical devices
designed to provide a number of several
critical functions. The energy necessary to
close and open the contacts of the vacuum
interrupters is stored in powerful opening
and closing springs. The closing springs are
normally charged automatically after a
closing operation, but there are provisions
for manual charging. The operating
mechanism that controls charging, closing
and tripping functions is fully trip-free. “Trip-
free” requires that the tripping function
prevails over the closing function as
specified in ANSI/IEEE C37.04.
Vacuum interrupter/operator module
The vacuum interrupter/operator module
consists of the three poles, each with its
vacuum interrupters and primary insulators
mounted to a common operating
mechanism housing. This module is shown
in Figure 11: Vacuum circuit breaker
operator module on page 24.
Construction
Each of the operator poles/phases are fixed
to the pole-mounting channel by four cast-
resin insulators. The insulators also connect
to the circuit breaker and ground switch
fixed-end pole heads and to the moving-end
connector box that in turn supports the
vacuum interrupter. The pole heads are
aluminum castings and the connector box is
a sheet-steel housing.
The energy-storing mechanism and all the
control and actuating devices are installed
in the mechanism housing. The mechanism
is of the spring stored-energy type and is
both mechanically and electrically trip free.
The close-open indicator, closing spring-
charge indicator and the operation counter
are located on the front of the operator
mechanism housing.
The control connector for the control and
signaling cables is a multi-contact plug. The
mating control plug wiring connects to the
terminal blocks in the relay and control
compartment.
