Construction (Refer To Figures 1, 2 And 5); Breaker Pole (Figure 5); Current-Path Assembly (Figure 5); Vacuum Interrupter (Figure 5) - Siemens 3AH Instructions, Installation, Operation, Maintenance

Interrupter/Operator Description

Construction (Refer to Figures 1, 2 and 5)

Each of the circuit breaker poles are fixed to the rear of the
operating mechanism housing by two cast-resin insula-
tors. The insulators also connect to the upper and lower
pole supports which in turn support the ends of the vacuum
interrupter. The pole supports are aluminum castings on
all circuit breaker ratings. Primary stud extensions may
be attached directly to the upper and lower pole supports.
The energy-storing mechanism and all the control and ac-
tuating devices are installed in the mechanism housing.
The mechanism is of the spring stored energy type and is
mechanically and electrically trip free.
The close-open indicator, closing spring charge indicator,
and the operation counter are located on the front of the
mechanism housing.
The control connector for the control and signalling cables
is a multi contact plug.
Figure 5. 3AH Pole Assembly

Breaker Pole (Figure 5)

The vacuum interrupter is rigidly connected to the upper
terminal and pole support by its terminal post. The lower
part of the interrupter is stabilized against lateral forces by
a centering ring on the pole support. The external forces
due to switching operations and the contact pressure are
absorbed by the struts.

Current-Path Assembly (Figure 5)

The current-path assembly consists of the upper terminal
and pole support, the stationary contact, and the moving
contact, which is connected with the lower terminal by ter-
minal clamp and a flexible shunt.

Vacuum Interrupter (Figure 5)

The moving contacts motion is aligned and stabilized by
guide bushing. The metal bellows follows the travel of
contact and seals the interrupter against the surrounding
atmosphere.
Switching Operation (Figure 5)
When a closing command is initiated, the closing spring,
which was previously charged by hand or by the motor,
actuates the moving contact through jack shaft, lever, in-
sulated coupler, and angled lever.
The forces that occur when the action of the insulated cou-
pler is converted into the vertical action of the moving con-
tact are absorbed by guide link, which pivots on lower in-
terrupter support and eye bolt.
During closing, the tripping spring and the contact pres-
sure springs are charged and latched by pawl (64.1 Figure
6). The closing spring of motor-operated breaker is re-
charged immediately after closing.
In the closed state, the necessary contact pressure is main-
tained by the contact pressure spring and the atmospheric
pressure. The contact pressure spring automatically com-
pensates for arc erosion, which is very small.
When a tripping command is given, the energy stored in
the tripping and contact pressure springs is released by
pawl (64.2 Figure 6). The opening sequence is similar to
the closing sequence. The residual force of the tripping
spring arrests the moving contact in the open position.

Operating Mechanism

The operating mechanism is comprised of the mechanical
and electrical components required to:
1. Charge the closing springs with sufficient potential en-
ergy to close the breaker and to store opening energy
in the tripping and contact pressure springs.
2. Mechanisms to release closing and tripping actions.
3. Means of transmitting force and motion to each of three
pole positions.
4. Operate all these functions automatically thru electri-
cal charging motor, cutout switches, antipump relay,
release (close and trip) solenoids, and auxiliary
switches.
5. Provide indication of the breaker status (open/closed),
spring condition (charged/discharged), and number of
operations.
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