QUESTION:
What are the derating factors for 3TF Contactors at higher
frequencies?
ANSWER:
At frequencies equal or higher than 100 Hz the thermal load rating
of switchgear is reduced. The reason for this is the so called
''skin effect'' at higher frequencies. This skin effect causes a
current flow near the surface of a conductor and not through its
full cross section. This effect is increasing with higher
frequencies.
As a result the thermal load rating (continuous current) of
contactors is reduced according to the following table:
--------------------------------------------------
- at 100 Hz: Ie AC-1 x 0,933
- at 200 Hz: Ie AC-1 x 0,871
- at 300 Hz: Ie AC-1 x 0,836
- at 400 Hz: Ie AC-1 x 0,812
--------------------------------------------------
Indicated are typical frequencies of practical applications.
Making- and breaking capacities are not reduced within this
range.
The contactors are not suitable for frequencies higher than 1000 Hz
since internal ferro-magnetic parts would be excessively heated by
eddy currents.
Entry ID:21267913
Date:2005-03-17
This entry is available in the following languages: german
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