Ampcontrol Pty Ltd – ABN 28 000 915 542
OCS USER MANUAL
MAG-182 Version 5 – FEB/2020
Uncontrolled Copy - Refer to Ampcontrol Website for Latest Version
APPROVED FOR EXTERNAL DISTRIBUTION
– PROPERTY OF AMPCONTROL PTY LTD
– NOT TO BE REPRODUCED IN PART
If the Short Circuit Output Relay setting is set to ‘CBR’, when a short circuit trip occurs, the circuit
breaker is opened and the main contactor left closed for one second to allow the circuit breaker time to
clear the fault. Any other trips or control actions to open the contactor during this time – except for earth
leakage, will be blocked.
8.3 Current Balance
Table 21: Protection Element – Current Balance Trip Characteristics
Open Main Contactor
Prevent Main Contactor from closing
Phase currents displayed in Amps.
The current balance measurement is available and is calculated as:
Where:
iav = the average of the 3 phase currents
MAX ∆ i = the maximum deviation of a phase current from the average.
The trip level is selectable at 5%, 10%, 20%, and 50% and off.
The phase current balance protection is inhibited until the average current exceeds both 20% of the
selected full load current and the selected balance trip level.
If the trip level is exceeded, a timer is triggered. If the imbalance remains above the set level for more
than two seconds the relay trips.
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