ABB VD4 Series Instruction Manual - page 21
Instruction manual 534/01 | VD4 Vacuum-circuit-breaker 21
4
Structure and function
4.1
Basic structure of the circuit-breaker on
withdrawable breaker assembly
(Figures 4/1 to 4/3 and 7/1)
The withdrawable part, which can be moved manually or by
a motor if fitted, consists of a steel sheet structure on which
the circuit-breaker with its ancillary components is mounted.
Insulated contact arms 6 with the spring-loaded contact sys-
tems 7 are fitted to the circuit-breaker poles. These create the
electrical connection to the panel when the withdrawable part
is inserted into the service position.
A multi-pole control wiring plug connector 8 connects the si-
gnalling, protection and control wiring between the panel and
the withdrawable part.
The withdrawable assembly and the circuit-breaker are con-
nected via a multi-pole control wiring plug connector 8.3.
As soon as the withdrawable part has been slid into the panel
and its base frame has engaged in the test/disconnected
position, it is positively connected to the panel. At the same
time, it is earthed by its travel rollers in their rails. The stored-
energy spring mechanism of the circuit-breaker, including
its controls and indicators, is accessible at the front of the
withdrawable part.
Withdrawable parts of the same version are interchangable.
With the same dimensions but different circuit-breaker equip-
ment, coding of the control wiring plug prevents impermissible
combinations of withdrawable parts and panels
4.2
Structure of the breaker poles
(Figures 4/2, 4/5 and 4/6)
The poles in column design are mounted on the bracket-
shaped rear part of mechanism enclosure 9.1. The live parts
of the breaker poles are enclosed in cast resin and protected
from impacts and other external influences.
With the breaker closed, the current path leads from the
upper breaker terminal 21 to the fixed contact 20.2 in the
vacuum interrupter 20, then via the moving contact 20.3 to
the lower breaker terminal 22.
The switching motions are effected by means of the insulated
link rod 26 with internal contact force springs 25.
4.3
Structure of the breaker operating mechanism
(Figures 4/4, 4/6 and 4/7)
The operating mechanism is of the stored-energy spring type.
The necessary operating energy is stored ready for activation
by charging the spring energy storage mechanism.
The stored-energy spring mechanism essentially consists of
drum 33 containing the spiral spring, the charging system,
the latching and operating mechanism and the linkages which
transmit the force to the breaker poles.
In addition, there are supplementary components such as the
charging motor, releases, auxiliary switches and the controls
and instruments located on the front of the mechanism enclo-
sure 9.1.
The operating mechanism is fundamentally suitable for auto-
reclosing and, due to the short charging times, also for multi-
shot auto-reclosing.
In the basic version of the circuit-breaker, the spring energy
storage mechanism is charged manually. The operating me-
chanism can optionally be fitted with a charging motor.
There is one rating plate with the main data of the switch
equipment on front plate 9.2, and another at the lower front
right in mechanism enclosure 9.1.
The basic version of the stored-energy spring mechanism is
fitted with the following auxiliary equipment:
- Shunt release OFF -MO1
- Five-pole auxiliary switch -BB2 for annunciation purposes
- Auxiliary switch -BB4 for fault annunciation
- Mechanical ON push-button 11
- Mechanical OFF push-button 12
- Mechanical position indicator 13
- Charging condition indicator 18 for the spring energy
storage mechanism
- Mechanical operating cycle counter 14.
The following additional equipment can be installed:
- Blocking magnet -RL1 with auxiliary switch -BL
- Shunt release ON -MC
- Second shunt release OFF -MO2
- Indirect overcurrent release -MO3
- Undervoltage release -MU
- Five-pole auxiliary switches -BB1 and -BB3
- Charging motor -MS
- Five-pole auxiliary switch -BS1 to switch the charging
motor.
4.3.1 Releases, blocking magnet and auxiliary switches
(Figures 2/15, 4/4, 4/7 and 8/1 to 8/3)
- The releases and the blocking magnet are moun ted at the
top left on the spring operating mecha nism.
- The allocation of the auxiliary switches can be seen in the
wiring diagram of figure 2/15.
- The five-pole auxiliary switch -BS1 is operated by the char-
ging condition indicator 18. It controls the charging motor
-MS, serves as an electrical interlock for shunt release ON
-MC when the spring mechanism is not sufficiently char-
ged, and also provides an electrical switching readiness
signal.
- Operation of the five-pole auxiliary switches -BB1, -BB2
and -BB3 is dependent on the switching position of the
circuit-breaker.
- Auxiliary switch -BB1 interrupts the circuit of the optional
additional shunt release OFF -MO2 with the circuit-breaker
in the open position, and the circuits of shunt release ON