Embedded communication card PPC322BE1

At the Minera Escondida the protection systems of the installed GMDs have operated. However, there have also been phenomena that have triggered the need to review specific protection functions and to improve them. A. Protection Against Network Disturbances The drive has a protection against over- and under-voltage as well as against over- and under-frequency. Specifically, these protections are implemented in the PSR processor program in the cluster called Interrupt 0.

1) Over-voltage protection at the network side The cycloconverter power part, as well the excitation converter, are protected via surge arresters against high and dynamic voltage peaks created by the network or by switching the converter transformers. This over-voltage protection especially protects the power semiconductor valves (thyristors) against the “avalanche breakdown”.

2) Line over- and under-voltage protection This protection function is realized inside the drive control software. Information of the actual network voltage at the high/medium voltage side is taken from the synchronizing transformer installed in the feeding switchgear (incoming side), and read in by the analogue inputs of the drive control system. The under-voltage and over-voltage detection immediately forces the blocking of all triggering pulses. Loosing the feeding voltage for any reason while triggering is still on-going, the emf voltage (electromagnetic force) of the motor as an alternating voltage would change its polarity and the motor would become a generator until it stops moving.