ABB VM1 Installation And Service Instructions Manual page 14

VM1 - USER MANUAL
14
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7. Operation
7.1.
7.1.1.
The magnetic actuator used in the VM1 circuit
breakers generates the run required to operate
the moving contacts of the interrupters and
integrates all the functions of a traditional
operating mechanism. The magnetic actuator is a
bistable system where end-of-run positions of the
moving armature are reached by means of
magnetic fields generated by two coils (one for
closing and one for opening). The moving
armature is kept in position by permanent
magnets.
The circuit breaker operations are obtained by
means of energisation of the opening or closing
Magnetic latching in end-of-run position.
Fig. 9
Operation of the circuit
breaker drive
Magnetic actuator
coil respectively. The magnetic field generated by
each coil attracts the moving armature and
thereby moves it from one of the latching points
of the permanent magnets to the other. The
capacitors which allow circuit breaker operation,
for a maximum time of two minutes, even in the
case of a drop in the auxiliary voltage, are
provided in the control circuit. In case of
emergency, the circuit breaker can in any case be
opened by means of a special crank handle which
acts directly on the moving armature of the drive.
Compared to a traditional operating mechanism,
the magnetic actuator has few moving parts and
greatly reduced wear even after a high number of
closing and opening cycles.
These characteristics therefore make it practically
maintenance-free.
Magnetic latching and action of the magnetic
field of a coil.
Moving armature in opposing position and
magnetic end-of-run latching.