HIGHVOLTAGESUPPLY
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DESIGN ENHANCEMENTS
The majority of product design enhancements and new
The ELR ® Series design can be
products developed and introduced by HVS ™ have been for
utilized to increase the maxi-
use in load tap changers. Most notable are new designs
mum current rating of off-
for electrical contacts. The company is nationally recog-
load, or de-energized, tap
nized for the ELR ® Series design that increases the maxi-
changers.
mum current rating of contacts, eliminating heating and
coking (carbon build-up).
The company has a proven reputation for redesigning
contact assemblies for enhanced performance. Utilizing
the latest contact design theor y, HVS ™ has successfully
redesigned contacts for a variety of reasons including
increasing current rating, extending ser vice life, and
facilitating installation and alignment.
7.
Components for Federal
Pioneer load tap changers
include enhanced epoxy formulation for tap head, diverter,
and selector switch molded components, and improved contact
designs for reversing, selector,
and diverter switches.
Barrier boards and other insulation components are
manufactured using a customized high-speed CNC router.
At customers request, ultrasonic testing can be per formed
to OEM specifications prior to fabrication.
Insulation components include arching chambers,
Electrical contacts and contact assemblies
shields, stand-off collars, drive shafts, and con-
are available for load tap changers
tact assembly bases and supports.
manufactured throughout the world.
ELR ® SERIES CONTACT DESIGN
Heating and coking of load tap
changer contacts occur when the
LTC is inactive for long periods or
subjected to loading that exceeds
maximum current rating of the
design. And while procurement
specifications can require that new
equipment perform under higher
loading condones, in many cases,
overall system reliability depends
upon design enhancements for many
of the existing load tap changers.
Development of the ELR ® Series contact design began in 1988 when
major utilities were experiencing
repeated load tap changer failures.
Heating and “Coking” (carbon build-up) of electrical contacts can
Failure analysis revealed that the
occur when load tap changers are inactive for long periods of time
contacts were heating and carbon
or subject to loading in excess of maximum current rating.
was precipitating out of the oil
The ELR ® Series design was
first used for reversing switch
contacts for the Ferranti
Packard 25RT32 and 138RT32
load tap changers.
onto the heated surfaces and forming a granulated, carbon-based deposit or
“coke.” The deposit acted as an insulator causing further heating.
Temperatures eventually exceeded the thermal operating limits of the contact
assembly, resulting in thermal failure.
The ELR ® Series contact design includes three fundamental design elements:
• Providing extra-low resistance contact points between moving and stationar y
contacts in reversing and diverter switches.
• Assuring retention of spring temper and contact pressure through the use of
stainless steel spring materials.
• Eliminating static connections and/or dividing contact tips into multiple
contact points
NEXT GENERATION COMPONENTS
Reverse engineering of existing components and research and
development of new designs are both integral parts of our business. Our efforts continue to provide solutions for known problems
and, from the engineering model we use, we have the ability to
identify and manufacture complex mechanisms and to address
future design issues as they are identified.
Manufacturing information is currently available for resistance,
vacuum and in-tank load tap changer designs. Shown below is
an in-tank load tap changer originally manufactured by Mitsubishi ®
in Japan. The project consisted of reverse engineering and
manufacturing of the complete diverter switch and resistor
assembly. Reverse engineering and design work consumed over
600 man-hours including over 400 man-hours of engineering time.
Reverse engineering
of the Mitsubishi ®
MRF-III in-tank
diverter and resistor
assembly required
600 man-hours of
analysis, testing,
and engineering
time.
ELR ® Series design
increases the maximum current rating of
reversing switch contacts for resistance
type load tap changers.
HIGH VOLTAGE SUPPLY™
9011 GOVERNORS ROW
DALLAS, TX 75247 USA
PHONE 214.637.4434
FAX 214.637.1157
www.hvsinc.com
H
TOLL FREE USA
800.338.5526
MEXICO
001.800.338.5526