8
9
3
Circuit-breaker on withdrawable part
3.1
Basic structure
(Figures 3/1 to 3/3 and 4/1 to 4/4)
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 (4.2) with the spring-loaded
contact systems (4.3) are fitted to the circuit-
breaker poles. These create the electrical connec-
tion to the panel when the withdrawable part is
inserted into the service position.
A multi-pole control wiring plug connector (10)
connects the signalling, protection and control wiring
between the panel and the withdrawable part.
The withdrawable assembly and the circuit-breaker
are connected via a multi-pole control wiring plug
connector (10.3).
As soon as the withdrawable part (13) 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 inter-
changable. With the same dimensions but different
circuit-breaker equipment, coding of the control
wiring plug prevents impermissible combinations
of withdrawable parts and panels.
Besides the design with mounted circuit-breaker,
withdrawable parts can also be supplied with other
fittings, e.g. for measurement purposes.
3.2
Interlocks/protection against maloperation
A series of interlocks are provided to prevent dan-
gerous situations and any maloperation. The inter-
locks of the panel system ZS and/or the mounting
frame, which are normally effective, are as follows
(concerning the circuit-breaker):
• The withdrawable part can only be moved from
the test/disconnected position into the service
position (and back) with the circuit-breaker open
and the earthing switch open (that means that the
breaker must opened before)
• The circuit-breaker can only be closed when the
withdrawable part is precisely in the defined test
position or service position (mechanical inter lock,
with additional electrical interlock for circuit-
breakers with electrical releases).
• The circuit-breaker can only be opened manu-
ally in the service or test position when no
control voltage is applied, and cannot be closed
(electromechanical interlock).
• Connection and disconnection of the control
wiring plug connector (10.2) is only in the test/
disconnected position possible.
• The earthing switch can only be closed when
the withdrawable part is in the test/disconnected
position or the removed position (mechanical
interlock).
• The withdrawable part cannot be moved from
the test/disconnected position into the service
position when the earthing switch is closed (me-
chanical interlock).
• Details of any additional interlocks, e.g. in connec
-
tion with a blocking magnet on the withdrawable
part and/or earthing switch operating mecha-
nism, can be found in the order documents for
each individual case (see also section 5.5.6).
• Details of typical interlocks for the panels can be
found in the panel documentation.
3.2.1
VD4 circuit-breaker run-on block
In case of any irregularity in the area of the inner
control mechanism and of the charging function of
the stored-energy spring mechanism, the run-on
block disables the immediately subsequent swit-
ching operation.
This is a protective measure to prevent damage to
the circuit-breaker
Release of run-on block may only be performed by
servicing personnel from ABB or adequately trained
specialist stuff.
BA 414-07_GB_AMC.indd 8
18.07.12 10:24
Summary of Contents for VD4 Series
Page 2: ......
