Ampcontrol OCS - 7.5 Main Contactor Protection

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
Page 36 of 72
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the pre-set threshold. Insulation tests apart from the generated insulation test via the Protection Element
should be still carried out on a regular basis for maintenance purposes.
7.5 Main Contactor Protection
There are four main contactor protection functions. Each of the functions monitors the states of the
outlets main contactor. If a fault is detected the upstream circuit breaker is opened (via the CBR output)
in order to remove power from the potentially faulty contactor.
7.5.1 Voltage Detection (Loss of Vacuum)
Table 13: Protection Element – Voltage Detection (Loss of Vacuum) Trip Characteristics
Parameter
Action
Power Cycle
Trip status maintained
Reset
Communication reset or physical reset after a trip. The physical reset
button is found on the front cover of the Protection Element
Trip Actions
Open Circuit Breaker
Prevent Main Contactor from closing
Active Period
When outlet is not running and the Back EMF timer has finished
counting down
Logging
Logged when a trip occurs
Parameters
Trip Level
Back EMF Timer
Monitoring
Phase voltages are continuously updated.
Loss of Vacuum provides a mechanism for checking that voltage is not present on the outlet after the
Main Contactor has opened. The levels at which the Main Contactor Failure should be initiated for
residual voltages are outlined in AS/NZS 2081:2011 Clause 9.2.1.
The Loss of Vacuum protection cannot be enabled immediately after the outlet is stopped as there is the
potential for Back EMF from the load to cause a trip. Subsequently, a Back EMF timer is provided and
allowed to elapse after the outlet has stopped, before the Loss of Vacuum protection can be operated.
AS/NZS 2081:2011 Clause 9.3 and Appendix H cover the requirements for Back EMF considerations for
Frozen Contactor devices where large inertial loads are connected.
The trip level can be selected at 25VAC or 50VAC. The trip time is less than 1sec.