Magnefix MD4
12
991.184 G01 03
2.1.5
The fuse panel
The fuse panel has a three-phase cable-connection point
and three fuse holders with removable caps. A mechanical
interlock ensures that the fuses cannot be replaced until
the switch caps of the branch-circuit panel have been
removed.
The connection contacts on the transformer side of the
fuse holder are deep in the holder so they cannot be
accidentally touched.
2.1.6
The protected panel
The protected panel has a three-phase cable-connection
point, a three-phase vacuum circuit-breaker with
autonomous switch-off function and a mimic diagram.
Using a vacuum circuit-breaker combined with the
protection relay enables overloads, short-circuits and
earthing fault currents to be switched off.
A mechanical lock ensures that the vacuum circuit-breaker
can only be switched on manually when the circuit is dead,
after the switch caps of the branch-circuit panel have been
removed
2.1.7
The busbar connecting panel
The purpose of the busbar connecting panel is to enable
two busbar systems to be connected. The connecting
panel is generally supplied without switch caps.
A connecting panel is used in redundant switchgear.
2.1.8
Switching on and off
R
EMARK
The following is a description of the switchgear.
For the procedures refer to Chapter 4.
Switching is achieved by fitting or removing switch caps. Be
sure to use a springing handle when performing this
operation. The switch caps ensure a double interruption of
each phase.
The fixed switch contacts are fitted to the busbar and the
cable connection point. They have replaceable arcing
chambers and arcing contacts. The 'on' switch cap is
secured by a strong permanent magnet (hence the name:
Magnefix).
The mobile switch contacts are housed in the switch caps.
They have arcing contacts and internal tripping and contact
force springs.
A ferromagnetic steel plate, to which the permanent
magnet can attach, is also fitted between the mobile
contacts. Fitted to the outside of the cast-resin insulated
member of the switch is a spring-mounted cam.
Switching on the switch caps
To switch on, put a switch cap on the springing handle.
Next, push the switch cap against the cam using the
switching handle. Push the springing handle to compress
its closing spring.
As soon as the force on the switch is more than the
resistance of the cam, the cap is pushed over the cam by
the action of the closing spring in the handle. Now the
switch contacts close: the main contacts first, followed by
the arcing contacts.
When switched on, the magnet and ferromagnetic plate
keep the switch caps in position. Next, remove the
springing handle from the switch cap.
Switching on a protected panel
To enable the panel to be switched on, first remove the
corresponding switch caps by pulling them out using the
springing handle. Next, manually switch on the three
phases of the vacuum circuit-breaker. Now the switch caps
are replaced one at a time.
The protected panel has a position indicator for checking
purposes
Incorrect switching operations are avoided thanks to the
use of mechanical interlocks.
Switching off the switch caps
To switch off, put the springing handle on the switch cap.
Next, pull off the cap. The main contacts are released first.
Simultaneously, the opening springs are tensioned, but the
magnet holds the arcing contacts closed. Pull with more
force to release the ferromagnetic plate. The opening
springs pull the arcing contacts out of the arcing chambers
at high speed.
Switching off a protected panel
A protected panel can be switched off as follows:
automatically by the autonomous switching off
mechanism;
manually by activating the switch-off push button.
Incorrect switching operations are avoided thanks to the
presence of a key interlock.
