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All about Motors
Motor protection |
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| Short-circuit rating of the main
circuit |
With currents that exceed the breaking capacity of the
motor starter in relation to the utilization category (EN 60947-1), it
is permissible for the current flowing during the operating time of the
protective device to damage the motor starter.
The permissible behavior of starters under short-circuit conditions is
defined in the so-called types of co-ordination (1 and 2). It is common
practice to state in the details of protective devices which type of
co-ordination is ensured by them.
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Type “1” co-ordination
In the event of a short circuit the starter must not endanger
persons and installations. It does not have to be fit for renewed
operation without repair.
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Type “2” co-ordination
In the event of a short circuit the starter must not endanger
persons and installations. It must be fit for renewed operation. There
is a risk of contact welding for which the manufacturer must give
maintenance instructions.
The tripping characteristic of the overload relay must not differ from
the given tripping curve after a short circuit.
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