ABB eVM1 Installation And Service Instructions Manual page 12

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6.1.2. Capacitor
The energy for operating the circuit-breaker is stored in one or two capacitors according to the
circuit-breaker model (fig. 5).
The capacitors are designed so that the energy for an O-C-O operating cycle is supplied without
the need for recharging.
The energy stored by the capacitor is constantly monitored by means of measuring the relevant
voltage.
The "UNIT READY" indication signals application of the power supply voltage and the "ready" state
of the circuit-breaker for the next operation.
The energy stored in the capacitors determines the position of the READY/NOT READY contacts
and lighting up of the luminous "UNIT READY" signal according to the following criteria:
• Case 1: circuit-breaker in the open position.
- The energy available is sufficient for one closing and opening operation.
• Case 2: circuit-breaker in the closed position.
- The energy available is sufficient for one opening operation.
- The energy available is sufficient for one opening operation within about 30 seconds from
interruption of the auxiliary power supply.
If the energy stored is not sufficient, the luminous "UNIT READY" signal is off, the "READY" contact
is open and the "NOT READY" contact is closed to indicate that the circuit-breaker is not ready for
the operation.
6.1.3. Position sensors
The use of two inductive position sensors (fig. 6) allows the state of the circuit-breaker (open -
closed - anomalous intermediate position) to be determined without the use of auxiliary contacts,
allowing continual monitoring of the system.
Fig. 5 Fig. 6