Before Energization; Operation - HPS DH Serie Guía De Instalación, Operación Y Mantenimiento

Before Energization

DANGER
HAZARD OF ELECTRIC SHOCK, EXPLOSION OR
ARC FLASH
Failure to install the transformer in accordance with
all applicable codes/ standards and the instructions
in this booklet will result in serious personal injury or
death and property damage.

Operation

DANGER
HAZARD OF ELECTRIC SHOCK, EXPLOSION OR
ARC FLASH
Failure to properly operate the transformer as per
all applicable codes and standards and the attached
instructions will result in serious personal injury or
death.
Installation, Operation, and Maintenance Guide - Low Voltage Transformers
For the safe and proper operation of the transformer,
please check and verify the following:
a) Ensure correct phase connections. Refer to the nameplate
vector diagram.
b) The load on a delta secondary winding with a 120 volt
center tap should not exceed the normal current rating
of the winding. This center tap is designed for a max. of
5% of the nameplate kVA.
c) When windings are connected in parallel (as in the
case of dual voltage primaries), the primary taps for all
coils must be connected to the identical percentage
tap positions to avoid the shorting of turns, or voltage
imbalances. For tap positions, refer to the nameplate on
the transformer.
d) The enclosure should be grounded with the appropriately
sized conductor as per local codes and standards
requirements.
e) The total load among all the phases should be balanced
as much as possible for optimum performance of the
transformers windings. The kVA loading on each phase
must not exceed 1/3 of the nameplate kVA rating of the
transformer.
f) The appropriate clearance and tightness of all electrical
connections should be checked.
g) Following the proper safety precautions, after energizing
and before connecting any loads, please measure
and verify the output voltage matches nameplate
specifications.
h) If there is any reason to suspect that the transformer has
been exposed to moisture during transit or storage, it
should be checked for dryness before energization. This
can be done by performing an insulation resistance test
(Megger Test). If any exposure to moisture is suspected,
the transformer must be dried out before energization by
following the dry-out procedures on page 12.
Under full load operating conditions, dry-type
transformers may appear warm to the touch, particularly on the
cover of the unit.
Standards permit the temperatures of the cover to reach
65°C (149°F) over ambient.
Dry-type transformers are designed to operate
continuously at their full nameplate kVA rating under normal
operating conditions.
ANSI C57.96 provides guidelines for loading transformers under
different operating conditions including:
Ambient temperatures that differ from the ambient

temperatures required for transformer operation. ANSI
recommends a maximum ambient of 40ºC.
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