ABB VD4 Series Instruction Manual - page 14
■
Shunt release OFF Y9 or
■
Undervoltage release Y4 or
■
Indirect overcurrent release Y7.
Note:
1. Shunt releases OFF (Y2) and ON (Y3) are exclusively
provided for opening and closing in normal 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 under voltage release (Y4) and/or indirect over current
release (Y7) are pure safety and protection releases and
must not be used for switching in normal operation
3.3 Function
3.3.1 Charging of the spring energy store
(Figures 3/3, 3/10, 6/2, 6/6, 7/7 and 7/8)
To provide the necessary motive energy, the spring energy
storage mechanism is charged via chain 55.34 fitted with
ratchet wheel 55.35, either automatically by a charging motor
or by hand in a vertical pumping action with charging lever
128. The current charging condition is shown at charging
condition indicator 55.8
As a precondition for an autoreclosing 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 3/4, 3/6, 6/1, 6/3 and 7/7)
The closing process is initiated manually by the double
bit key 145 and the ON-OFF operating shaft 54, or electrically
by activation of shunt release Y3. The release mechanism
then permits drive shaft 55.30 to be rotated by the (previously)
charged spiral spring. The moving contact 58.3 in vacuum
interrupter 58 is moved until the contacts touch by cam disk
and further kinematic links. In the further sequence of motion,
spring arrangement is tensioned and the appropriate amount
of contact force thus applied. The available overtravel is
higher than the maximum value of contact erosion during
lifetime of the interrupter. During the closing process,
opening springs are simultaneously tensioned.
3.3.3 Opening procedure
(Figures 3/3, 3/6, 6/3 and 7/7)
The opening procedure is initiated manually by the double
bit key 145 and the ON-OFF operating shaft 54, or electrically
by activation of one of the releases Y2, Y4, Y7 or Y9.
Release mechanism then permits drive shaft 55.30 to be
turned further by the spring energy storage mechanism,
which is still sufficiently charged. The opening spring, which
is thus released, moves the contact 58.3 into the open position
at a defined speed.
3.3.4 Autoreclosing sequence
An OFF-ON or OFF-ON-OFF autoreclosing sequence 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 chamber 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
extremely low, which has advantageous effects on the life
of the contacts and thus on that of the vacuum interrupters.
14 Structure and function | VD4 Vacuum Circuit-breaker