Analog input terminal board PPC322BE1 HIEE300900R1

2) Electrical Aspects First of all, the parameter settings were adjusted such that the drive would remain within its design limits. Thus, the stator over-current limits were adjusted, the medium voltage circuit breaker opening time in case of over-current was elongated and the drive control was fine tuned for maximum speed and load. Furthermore, changes in the hardware and software of the PSR controller were implemented.

These changes were made according with the results of the investigation and simulations under worst case conditions of a two-phase short circuit. The control is capable of detecting those conditions when the probability of a dangerous two-phase short circuit is very high. Once these conditions are fulfilled, this new protection function will force a three-phase short circuit by firing all thyristors of the cycloconverter at the same time, while avoiding a twophase short circuit.

This protection function was implemented in all GMD systems at Escondida to avoid two-phase short circuits and to reduce the resulting forces acting on the ringmotor stator fixation. For implementing this protection some consideration were taken into account:

• The introduction of the “firing all release” has to take place without circulating currents via the cycloconverter transformers.