16
Construction
The essential parts of the operating
mechanism are shown in Figure 8: Magnetic-
actuator operating mechanism on page 15.
The essential parts of the magnetic actuator
(101.0) are the side plates, cover plate,
permanent magnets, coupling rod, coil,
armature parts and bearing plate for
armature.
The magnetic actuator (101.0) is connected
by the side plates with the mechanism
housing (60.0). Also, the magnetic actuator
(101.0) secures to the jack shaft (63.0). The
magnetic actuator (101.0) requires no
maintenance.
If the circuit breaker is stored for a long time
without control power, the capacitors will
fully discharge. Charge the capacitors at least
every two years for a minimum of three
hours.
If the capacitors have been fully discharged
for a very long time, charging time may be
significantly longer than indicated. If
capacitor charging time is much longer than
expected on initial energization, refer to
“Capacitor charging after very long de-
energization” on page 40 of the
“Maintenance” section of this instruction
manual.
Apply control power to the power terminals
as shown on the drawings specific to the
order on which the circuit breaker was
supplied. Refer to the example of circuit
diagram shown in Figure 14 on page 24.
Mode of operation
The capacitors have been charged, the
mechanism is ready for an operation at any
time. This is indicated by the green LED
(105.1) on the front panel. If the control
voltage fails, the stored energy is sufficient
for one open operation initiated by the
operator-mounted Open pushbutton (54.0)
within five minutes. Within five minutes after
loss of operator control power, the circuit
breaker can perform one open operation
initiated by a remote command if the remote
command is from a wet (powered) contact.
Closing
There are two different closing operations
possible:
Remote (electrical)
Local (electrical) (by pressing the
pushbuttons).
When a close command is initiated, the
capacitors supply current to the actuator coil,
creating an electromagnetic field. This field
adds to the magnetic field of the permanent
magnets. As a result, the coupling rod (62.8)
moves upward. In turn, this transfers force to
the jack shaft (63.0) by means of the
coupling link (62.9), closing the circuit
breaker. Simultaneously, the opening spring
(64.0) is compressed.
Trip-free function
For the type SDV7-MA outdoor distribution
circuit breaker, the trip-free function is
embedded in the controller electronics.
Opening
When an opening command has been given,
a reverse current is supplied to the magnetic-
actuator coil (101.3). This cancels the
attractive force between the magnetic
actuator armature and the permanent
magnet. Due to the stored energy of the
contact pressure spring (49.0), the magnetic-
actuator’s armature is pushed downwards.
This opening process is supported by the
opening spring (64.0). In the OPEN position,
the opening spring assures that the ambient
atmospheric pressure does not close the
contacts in the vacuum interrupters (30.0).
