Howard HI-102 Overhead Transformer - Manual (Page 15)

Document 2.4.95, Revision 0
May, 2013
15
Fluid-Filled Overhead Distribution Transformers
multiple high-voltage windings. Although not recom-
mended, these transformers also can be designed
with both high-voltage taps and multiple high-voltage
windings. When both are provided, extreme care
must be taken to ensure that the tap switch setting
is in the position shown on the nameplate when the
multiple-voltage switch is in the parallel position.
Failure to set the tap switch in the correct position
could result in an unsafe condition.
Step-up/step-down transformers (transformers with
a low-voltage rating of more than 600 Volts) can be
provided with high-voltage and/or low-voltage taps,
or with multiple high-voltage and/or low-voltage
windings.
Tap switches and multiple-voltage switches are suit-
able for de-energized operation only. Never operate a
tap switch or multiple-voltage switch while the trans-
former is energized. These switches are typically
provided with an external operating handle, but when
specified can be designed for internal operation and
accessed by removing the transformer cover or, if
provided, the handhole cover. Before removing the
transformer cover or handhole cover, refer to “Open-
ing the Transformer Tank” for instructions.
To operate the tap switch or multiple-voltage switch
on a de-energized transformer, first disengage the
locking screw, if provided, and then rotate the switch
handle to the desired position as indicated on the
switch dial plate or switch body and on the trans-
former nameplate. After verifying that the switch is
set to the desired position, re-engage the locking
screw, if provided, to prevent accidental operation of
the switch.
Tap Switch
The de-energized tap switch may be used to adjust
the voltage ratio of a transformer. It is intended to
allow adjustment of the output (secondary) voltage
to the rated value. Tap switches usually have five or
seven tap positions as indicated on the switch dial
plate or switch body and on the transformer name-
plate. Do not use the tap switch to raise or lower the
output voltage to any other than the rated voltage
indicated on the transformer nameplate. If the tap
switch is set to provide an output voltage different
from rated secondary voltage, improper transformer
operation will occur.
▲
! WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW COULD RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND COULD ALSO RESULT
IN DAMAGE TO THE EQUIPMENT.
• Do not operate a de-energized multiple-volt-
age switch unless the transformer is com-
pletely de-energized.
• Do not re-energize the transformer unless
the multiple-voltage switch handle or cap is
secured in the desired position.
The transformer is usually shipped from the factory
with the tap switch set to the rated voltage position,
unless otherwise specified. Always check the tap
switch position to make sure it is set correctly.
Multiple-Voltage Switch
The de-energized multiple-voltage switch is used to
allow operation of the transformer on multiple sys-
tem voltages. Switch positions and available ratings
are shown on the transformer nameplate. Unless
otherwise specified, transformers with multiple-
voltage windings are shipped from the factory with
the multiple-voltage switch set to the highest voltage
position.
▲
! WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS BE-
LOW COULD RESULT IN MINOR OR MODERATE
PERSONAL INJURY, AND COULD ALSO RESULT
IN DAMAGE TO THE EQUIPMENT.
• Do not operate a de-energized multiple-
voltage switch unless the transformer is
completely de-energized.
• Do not re-energize the transformer unless
the multiple-voltage switch handle or cap is
secured in the desired position.
Fuses
A blown fuse may indicate a faulted transformer. Do
not replace a blown fuse unless the cause of the
fuse operation has been identified and corrected.
Fuses should be applied according to the fuse rating.