13
five NOCs to five NCCs. Its contacts are availa-
ble for any required control, annunciation or in-
terlock functions. The auxiliary switch is normally
configured as shown in figure 7/5.
• The single pole auxiliary switch -S7 (fleeting con-
tact time
≥
30 ms) serves to provide a fault signal
("breaker released").
With remote control, the auxiliary switch is
necessarily operated by:
– Shunt release OFF -Y2 or
– Shunt release OFF -Y9 or
– Undervoltage release -Y4 or
– Indirect overcurrent release -Y7.
Note:
1. Shunt releases OFF (-Y2) and ON (-Y3) are ex-
clusively provided for opening and closing in nor-
mal operation. For safety breaking operations,
the second shunt release OFF (-Y9) must be
used, in most cases with a separate control
voltage supply.
These three releases are of the solenoid type
and suitable for a large number of operating
cycles.
2. The undervoltage release (-Y4) and/or indirect
overcurrent release (-Y7) are pure safety and
protection releases and must not be used for
switching in normal operation.
3.2.2
Mounting of the VD4 on trucks from other
manufacturers
VD4 circuit-breakers which are not installed on
ABB withdrawable parts must be fitted with one or
two additional auxiliary switches which are
dependent on the mechanical lock and release
device. These must interrupt the circuit of shunt
release ON -Y3.
Similary to auxiliary switches -S8 and -S9 in ABB
withdrawable parts, no electrial pulse may arrive
during and before mechanical blocking of the spindle
mechanism, and may only be applied again after the
end of mechanical blocking.
This ensures that the shunt release ON cannot be
loaded with an electrical ON pulse when the
withdrawable part is in an intermediate position,
which could burn out the coil.
3.3
Function
3.3.1
Charging of the spring energy store
(Figures 3/1 and 3/4)
To provide the necessary motive energy, the
spring energy store, either charged automatically
by a charging motor or manually in a vertical
pumping action with charging lever 9, depending
on the equipment fitted to the circuit-breaker. The
current charging condition is shown at charging
condition indicator 8.
As a precondition for an auto-reclosing sequence,
the operating mechanism is either (re-)charged
after a closing operation automatically by the
charging motor, or it requires (re-)charging by
hand if the operating mechanism is of the manual
type.
3.3.2
Closing procedure
(Figures 3/1, 3/4 and 3/5)
The closing process is started by the mechanical
ON push-button 2, or by activation of shunt re-
lease ON -Y3. The release mechanism 31 then
permits drive shaft 30 to be rotated by the (previ-
ously) charged spiral spring. The moving contact
15.3 in vacuum interrupter 15 is moved until the
contacts touch by cam disk 21 and further kin-
ematic links. In the further sequence of motion,
spring arrangement 17 is tensioned and the ap-
propriate amount of contact force thus applied.
The available overtravel is higher than the maxi-
mum value of contact erosion during lifetime of the
interrupter. During the closing process, opening
springs 19 are simultaneously tensioned.
3.3.3
Opening procedure
(Figures 3/1, 3/4 and 3/5)
The opening procedure is initiated by mechanical
OFF push-button 3 or by activation of one of
releases -Y2, -Y4, -Y7 or -Y9. Observe the notes in
section 3.2.1 on control of the releases. Release
mechanism 31 then permits drive shaft 30 to be
turned further by the spring energy store, which is
still sufficiently charged. Opening spring 19,
which is thus released, moves contact 15.3 into
the open position at a defined speed.
3.3.4
Auto-reclosing sequence
An OFF-ON or OFF-ON-OFF auto-reclosing se-
quence is activated and checked by the protection
system. It is necessary for the spiral spring in the
operating mechanism to be in the (re-)charged
condition, with the circuit-breaker in the closed
position. The (re-)charging process is carried out
automatically after closing of the breaker on
breakers with motor charging mechanisms, but
must be carried out manually on breakers without
charging motors (or when the charging motor has
broken down). Opening of the breaker is also
possible during the (re-)charging process, but sub-
sequent closing of the breaker is however blocked
until the charging process has been completed.
3.3.5
Quenching principle of the vacuum interrupter
Due to the extremely low static interrupter cham-
ber pressure of 10
-2
to 10
-6
Pa, only a relatively small
contact gap is required to achieve a high dielectric
strength. The arc is extinguished on one of the first
natural current zeros.
Due to the small contact gap and the high
conductivity of the metal vapour plasma, the arc
drop voltage, and additionally, due to the short
arcing time, the associated arc energy, are extre-
mely low, which has advantageous effects on
the life of the contacts and thus on that of the
vacuum interrupters.
