Maintenance; Dry-Out Of Transformers; Accessories - HPS NH Serie Guía De Instalación, Operación Y Mantenimiento

transformers under different conditions including:
 Ambient temperatures that are varied from the
ambient temperatures required for transformer
operation.
 Short time overload as it relates to time and
temperature and the corresponding loss of life of
the transformer.
 Overload that results in a reduction of life
expectancy of the transformer.
If the transformer is experiencing increased
temperatures, the following load characteristics
should be considered immediately:
 Rigorous motor starting loads or other impact
type loading for which a specific transformer for
that application is required.
 Over-excitation of unit due to excess supply line
voltage or current.
 Ambient temperatures above standard.
 Overload beyond ANSI C57.96 guidelines.
 Harmonic distortions of the supply line voltage
and currents.
If overheating is noted, any attempt to add
supplemental fan cooling must be in accordance with
factory installation guidelines. Incorrectly installed fans
can misdirect the airflow and cause serious
deterioration of the insulation life in a transformer coil.
Dry-type transformers can be shut down and
stored for extended periods of time without any
deterioration. Care must be exercised to clean and dry
units prior to energization, as previously outlined.

MAINTENANCE

Under normal operating conditions and
environments, dry-type transformers do not require
maintenance. However, periodic care and inspection is
a good practice particularly dependent on the
environmental conditions in which the unit is installed.
Peripheral inspection and external dust removal
may be carried out while the transformer is in
operation. However, access covers must not be
opened under energized conditions.
Internal maintenance must be performed
with a transformer de-energized, isolated
and with the terminals grounded.
Maintenance would include internal cleaning,
tightening of links and bolted connections, servicing
and inspection of auxiliary devices.
Air ducts should be free of any accumulation of
dust and debris and any bolted connections of
terminals must be in good condition.
Vacuuming or blowing of compressed air from
the top down is an accepted practice for removing dust
from the ducts of a transformer coil. Low pressure, dry
air should be used to avoid further contamination of
the windings by foreign material.
The ground connection should also be checked to ensure a low impedance connection. The
accumulation of ice, snow or any other object blocking
the ventilation should be cleaned up immediately
during the operation of the transformer.
On outdoor units where filters have been
installed, being exposed to the outside atmosphere
can cause the filters to get dirty quickly. A periodic
check of the filters will help avoid filter clogging and
thus transformer overheating. Also, never run the
transformer without the filters properly in place.

DRY-OUT OF TRANSFORMERS

In the event that transformers have been
exposed to moisture such as condensation or rain, it is
advisable to dry-out any unit prior to energization.
Drying may be accomplished by using any hot or
warmed air, radiant heat or internal heat that is
directed through the windings. Heated air should be allowed to rise up through the windings for a minimum
of twenty four (24) hours after the evidence of
condensation is no longer visible.
Transformers that have been exposed to flood
conditions, direct rain or sprinklers, may not be able to
be dried out appropriately. Contact the transformer
manufacturer for appropriate action.

ACCESSORIES

Dry-type distribution transformers are available
with a number of accessories to facilitate installation.
Consult your local dealer or distributor for the
purchase of any of the items which may be carried in
inventory.
1) Wall Mounting Brackets
Encapsulated transformers have integral wall
mounting capabilities for units up to 285 lbs. Units over
285 lbs. must be floor mounted only.
Ventilated dry-type transformers are normally
designed to be floor mounted only. However, some
ventilated units up to 51kVA are supplied in enclosures
that have integral wall mounting capabilities. These
units can be conveniently mounted on walls, beams or
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