Electrical and thermal protections
protections must be chosen based on the specific running conditions, according to standards
EN 60204-1 (for ATEX motors, see also EN60079-14 and EN61241-14).
External protections
It is possible to have:
1. Protection against overloads. A thermal cut-out relay, which
automatically controls a knife switch.
2. Protection against peak currents by magnetic relay that controls
an automatic knife switch, or by fuses; these must be set to the locked rotor current.
3. if the application requires, protection against excessive speed of the electric motor, for
example if the mechanical load may drive the electric motor itself and thereby create a
hazardous situation.
4. If special conditions or synchronised operation with other machines or parts of machines
require it, protection against power failures or dips by means of a minimum voltage relay
that controls an automatic power knife switch.
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General