1
1. Disconnectors
1.1 General
OJON-disconnectors which are of knife type, meet the
requirement of VDE and IEC standards. The technical
data and dimensions are shown in catalogue "OJON
indoor type disconnectors" (OJON 4 GB).
1.2 Construction and operation
The base of the disconnectors is made of plate and the
insulators of brown cast resin. The insulators of 1 kV
disconnectors are plain cylinders whereas 10 and
20 kV insulators are with sheds.
The contacts in 1000-4000 A disconnectors are of cast
copper. For other disconnectors they are made of cop-
per plate. Flat bar or U-profile copper is used for the
knives. Silver plating of the contacts and knives is ample
against wear. Depending on the current rating one or
more pairs of knives are used. The contact force is
achieved by spiral springs compessing the half knives
together.
1-pole disconnectors are provided with an operating ear
between the knives. A latch device connected to the
operating ear locks the knives to the contacts in a closed
position. An operating shaft in the base of the 3-pole
switch moves the knives through levers and insulated
intermediate rods. The shaft diameter is 25 mm and
the turning angle 90
o
. The base of the disconnectors is
painted grey whereas the knives are red for their posi-
tion to be more easily distinguished.
1.3 Accessories
OJON-disconnectors are available with following
accessories:
- earthing knives
- busbar joint
- auxiliary switch
- operating arm
- operating rod
- manual operating mechanism
- locking device
- interlocking coil
- shaft extension
- support bearing
Fig. 1
Earthing knives
The earthing knives can be installed above or below the
disconnector. They are provided with a stepping device
which prevents them from being moved by their own
weight. The main and earthing knives are also inter-
locked so that they cannot be closed simultaneously.
The same types of operating devices apply to the earth-
ing knives as to the disconnectors in general.
Busbar joints
Busbars can be connected to the 2500 A and 4000 A
disconnectors using separate joining pieces, which
obviate making 90
o
bends on the busbars.
Auxiliary switch
The auxiliary switch is fixed to the wall of the cubicle or
to the frame of the disconnector. The auxiliary switches
are available with 6 and 9 switching elements each with
a change-over contact. Instructions for erection and
operation are supplied with the switch.
Manual operating mechanism
The manual operating mechanism locks the disconnector
at its end positions. The end of the control shaft can be
covered by means of a lockable protection cover. The
manual operating mechanism can be equipped both with
an interlocking magnet and an auxiliary switch.
Summary of Contents for OJON
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