Description
5.5KV MV E-RATED MEDIUM VOLTAGE
E-RATED MEDIUM VOLTAGE FUSES
Description
E-rated fuses have time current characteristics designed to
provide current-limiting protection for power transformers,
potential transformers, power centers, feeder centers, and
unit sub stations. When properly applied, they can protect
against high and low fault currents.
NEMA Standards for E-rated medium voltage fuses require
that fuses rated 100E or less open within 300 seconds
(5 minutes) when subjected to an RMS value of 200-240%
of the fuse continuous current rating; and fuses with an
E rating larger than 100E must open within 600 seconds
(10 minutes) when subjected to an RMS current of 220-
240% of the fuse’s continuous current rating. These values
establish one point on the time-current curve.
Application Note
Since these fuses are used for the protection of general
purpose circuits which may contain transformers, motors,
and other equipment producing in-rush and/or overload
currents, fuses should generally be rated at 140% of the
normal full load current, and circuits should be analyzed
to ensure that system load currents will not exceed the
current rating of the fuse
