ABB VD4X, Instruction Manual

S T R U C T U R E   A N D   M O D E   O F   A C T I O N

15

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Structure and mode of action

3.1 Structure of the breaker poles

(Figures 3/1 to 3/3)

The horizontally arranged poles are mounted on 

mounting plate 9 at the rear part of breaker 

operating mechanism 1. The live parts of the 
breaker poles are located in the insulating
material 11.

With the breaker closed, the current path leads 
from breaker terminal 13 at the front via the 

contacts in vacuum interrupter 15 to connecting 

bar terminal 12 above or below the breaker pole.

Switching motions are initiated by actuating rod 17.
See figures 3/1 and 3/2.

The basic structure of a vacuum interrupter is 

shown in figure 3/3.

3.2 Structure of the operating mechanism

(Figures 3/1 to 3/8)

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 operating mechanism essentially consists 

of drum 23 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 releases and 
the controls and instruments located on the front 
of the enclosure.

The operating mechanism is fundamentally 
suitable for auto-reclosing and, due to the short 
motor charg ing times, also for multi-shot auto- 
reclosing.

The spring energy storage mechanism is charged 
by a motor (external activation and deactivation). 
Emer gency manual operation with a charging 
lever is possible.

There are rating plates with the main data of 
the switching device at front plate 1.1 and at the 
right of the mounting plate.

3.2.1 Operating mechanism equipment

1. Basic operating equipment:

•  Shunt release OFF -Y2
•  Shunt release ON -Y3
•  Mechanical ON push-button (2)
•  Mechanical OFF push-button (3)
•  Rotational auxiliary switches -BGB for 

annunciation purposes

•  Auxiliary switch -S7 for fault signalization
•  Mechanical position indicator (4)

•  Mechanical charge-state indicator (8) for 

the energy storage spring mechanism

•  Mechanical operating cycle counter (5)
•  Charging motor
•  Micro-switches -S1 for switching of the 

charging motor

•  Mechanical interlocks

-   Circuit-breaker/three position 

disconnector

-   Blocking magnet on circuit-breaker 

(optional)

-   Blocking of undervoltage release in the 

case of earthing

2. Additional equipment:

•  Second shunt release OFF -Y9
•  Undervoltage release -Y4
•  Indirect overcurrent release -Y7

Blocking magnet -Y1 mechanically blocks the 
ON half shaft on failure or absence of control 
voltage, and simultaneously uses the 
corresponding rotational auxiliary switch
contact to interrupt the circuit of shunt release 

ON -Y3.

The wiring diagram for the circuit-breakers can 

be found in Figure 3/9 & 3/10.

3.3 Mode of action of the circuit-breaker

(Figures 3/1 to 3/8)

3.3.1 Charging of the spring energy storage 

mechanism

To provide the necessary motive energy, the 
spring energy storage mechanism is charged 
either auto matically (external activation and 
deactivation) by a charging motor or in 
emergency manual operation with a vertical 

pumping action with charging lever 32, 

depending on the equipment fitted to the
circuit-breaker. The charging condition is shown 

by mechanical charging condition indicator 8.

As a precondition for an auto-reclosing sequence, 
the mechanism is automatically (re-)charged 
after a closing operation by the charging motor.

3.3.2 Closing procedure

The closing process is started by activation of 

shunt release ON -Y3, or by the mechanical ON 
push-button. The release mechanism 24 then 
per mits mechanism shaft 27 to be rotated

by the (previously) charged spiral spring. The 

moving con tact 15.3 in vacuum interrupter 15 is 
moved by cam disc 28 and further kinematic 

links until the contacts touch. In the further 

sequence of motion, spring arrangement 16 is

tensioned and the approp riate amount of 
contact force thus applied. The available 
overtravel is greater than the maximum contact 
erosion during the service life of the vacuum
interrupter. During the closing process, opening 

springs 25 are simultaneously tensioned.

3.3.3 Opening procedure

The opening procedure is initiated by activation 

of one of releases -Y2, -Y4, -Y7 or -Y9

 or by 

mechanical OFF push-button 3. Release 
mechanism 24 then permits mechanism shaft 27

to be turned further by the spiral spring, which 
is still sufficiently charged. The opening spring 

25, which is thus released, moves the contact 15.3

into the open position at a def ined speed.

Notes on activation of the releases

1. Only shunt release OFF (-Y2 and -Y9) and 

shunt release ON (-Y3) are provided for 

operational opening and closing.

These three releases are rotary magnets, and 
are suitable for a high number of operating 
cycles.

2. The undervoltage release (-Y4) or the indirect 

overcurrent release (-Y7) are purely 

safety/protective tripping units and must not 
be used for operational switching.

3.3.4 Auto-reclosing sequence

An OFF-ON or OFF-ON-OFF auto-reclosing 
sequence is activated and monitored by the 
protection system. It is necessary for the spiral 
spring in the operating mechanism to be in the 
(re-)charged cond ition, with the circuit-breaker 
in the closed position. The (re-)charging process 
is carried out auto mat ically by the charging 
motor after closing of the breaker. If the charging 
motor breaks down, the charging process can 
be carried out or completed manually. Opening
of the breaker is also possible during the 
(re-)charging process, but subsequent 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 <2x10

-7

 hPa, only a 

relatively small contact gap is required to 
achieve a high dielectric strength. The vacuum
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.

 276.5