DCB r e a k
– InstructIons for InstallatIon, servIce and maIntenance
8
6.4. Control circuit
The circuit breaker is kept in the closed position by a
holding current of around 10% of the current
absorbed during the closing operation. The circuit
breaker opens automatically when the holding
current is zeroed by the circuit having opened.
Closing
The -SFC button closes the auxiliary switches -KFA1
and -KFA3. Closing contacts -KFA1 feeds the -MBC
electromagnet and the main contacts of the high
speed circuit breaker -QAB.
Hold
After about approximately 500 ms the delayed
contact -KFA3 closes and feeds the contactor -KFA2.
The contacts -KFA2 open by inserting the -RAR
resistor: the current decreases to a proper value to
maintain the circuit breaker in closed position.
Opening
Opening of the pushbutton -SFO causes the zeros
of the current in the electromagnet -MBC and the
opening of the main contacts of the high speed
circuit breaker -QAB.
—
6. Characteristics
