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and the cover in place, and preferably with the case
mounted on a swtichboard panel. If the relay time
is to be checked from a cold start, the relay should
have been de-energized for several hours
beforehand. If the overload is to be applied follow-
ing a constant load, the current must be main-
tained at the constant initial value until there is no
further change in the moving contact position
before applying the overload. Both the load and
overload currents must be carefully regulated
throughout the test. The relay should not be sub-
jected to drafts or sudden changes in temperature
during the test, as there is some delay in the
response of the temperature compensation. In the
factory calibration the relay is held in a controlled
temperature and other precautions are taken to
minimize factors which would introduce calibra-
tion errors.
The test current should be interrupted as soon
as the contacts close in order to avoid possible
damage to the heaters, particularly when testing at
high values of overload.
Courtesy of NationalSwitchgear.com
RENEWAL PARTS
Repair work can be done most satisfactorily at
the factory. However, interchangeable parts can be
furnished to the customers who are equipped for
doing repair work. Completely assembled and
calibrated thermal elements can be furnished, but
individual parts for the thermal element should not
be ordered since factory fixtures and equipment
are necessary for satisfactory assembly and
calibration. When ordering parts, always give the
complete nameplate data.
ENERGY REQUIREMENTS
The burdens of the heater unit plus the 6-50
ampere instantaneous unit in series at 5 amperes
60 cycles is as follows:
Heater
lap Llnk Continous
Amp
Position
Rating
Watt Volt-Amp power Factor
3.5
Open
6.25
5.0
Closed
3.25
I . L . 41-553.1G
1.0
6.25
1.0
3.25
1 7
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