Cable Connections - HPS DH Serie Guía De Instalación, Operación Y Mantenimiento

Cable Connections

DANGER
HAZARD OF ELECTRIC SHOCK, EXPLOSION OR
ARC FLASH
Failure to follow these instructions will result in
death, serious injury or property damage.
Never attempt to change connections or taps
unless the transformer is de-energized and all
windings grounded.
Installation, Operation, and Maintenance Guide - Low Voltage Transformers
The connecting cable size is determined from the line
current rating of the transformers primary and secondary
windings and may be selected from the information in appendix
A (page 14). Use wire rated for at least 90°C (194°F) and sized
on the basis of 75°C (167°F) ampacity. Use with AL9CU-AL-CU
lugs. Electrical Connector Lugs, if provided, are to be used with
SIW, Class B or Class C cables or wires only.
Conveniently located pre-punched knockouts are provided
on all ventilated transformer enclosures up to 150 kVA three
phase and 100 kVA single phase, to facilitate cable entry.
For non-ventilated transformers, pre-punched knockouts
are not provided and the appropriate cable connector suitable
for the application must be used. Please refer to Appendix
E (page 17 to 19) for cable entry locations. If a transformer
must be relocated to make the necessary cable connections, all
safety requirements and the related lifting procedures must be
followed.
Cable Connection Requirements
Side entry of cables is recommended as it leaves the ventilated
areas unobstructed.
For standard ventilated DH type 3R enclosures, bottom

entry is permitted only in the areas defined in Appendix
E.
The proper performance of the transformer is dependent

on unrestricted airflow entering the bottom ventilation
slots and exiting through the top ventilation slots.
Blocking the bottom ventilation intake with bottom entry

conduits/ cables in the area defined between the bottom
entry plate, the inside of the transformer legs and the
ground floor may result in overheating the transformer.
For DH type enclosures where bottom entry is permitted

in the designated areas, a maximum of 50% of the
front bottom area described above may be blocked with
conduits/ cables. In extreme cases no more than 70% of
this area may be obstructed, but only under the condition
that in this case the clearance listed on the nameplate is
maintained on all sides of the transformer (both sides,
front and back).
Offset connectors are also available to help with cable

connections to terminal pads, to reduce the bending
space for the cables
Cable connection lugs of plated copper or aluminum
may be used to connect to the transformer terminals.
Terminals should be cleaned and electrical joint compounds are
recommended for use on all electrical connections.
Refer to the transformer nameplate for primary and
secondary voltage connection combinations and primary and/or
secondary tap positions as applicable.
Transformers received from the factory will have tap leads
installed on the nominal, or 100%, voltage position. The taps
8