PM630 PM632 PM633 ABB DCS system controller processor module

PM630 PM632 PM633 ABB DCS system controller processor module

PM630 PM632 PM633 ABB DCS system controller processor module

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The back-up protection is an “over-current coordination of two over-current

protective devices in series where the protective device, generally but not

necessarily on the supply side, effects the over-current protection with or without

the assistance of the other protective device and prevents any excessive stress

on the latter” (IEC 60947-1, def. 2.5.24).

Besides, IEC 60364-4-43, § 434.5.1 states: “… A lower breaking capacity is

admitted if another protective device having the necessary breaking capacity is

installed on the supply side. In that case, characteristics of the devices, must

be co-ordinated so that the energy let through by these two devices does not

exceed that which can be withstood without damage by the device on the load

side and the conductors protected by these devices.”

The switch disconnectors derive from the corresponding circuit-breakers, of

which they keep the overall dimensions, the fixing systems and the possibility

of mounting all the accessories provided for the basic versions. They are devices

which can make, carry and break currents under normal service conditions of

the circuit.

They can also be used as general circuit-breakers in sub-switchboards, as

bus-ties, or to isolate installation parts, such as lines, busbars or groups of

loads.

Once the contacts have opened, these switches guarantee isolation thanks to

their contacts, which are at the suitable distance to prevent an arc from striking

in compliance with the prescriptions of the standards regarding aptitude to

isolation