Page 7 - Energize August 2022

COVER STORY

Typical design characteristics are:
Core
The core is made of high-quality, grain-oriented, cold-rolled silicon
steel of high magnetic conductivity, by using 45 five-step overlapping
method to reduce the no-load loss and no-load current. Simulation
analysis method is applied for the core design thus the vibration
frequency and scale are calculated precisely and effectively. Flexible
connections are adopted between the core and coils, and core and
clamps. With these measures, the transformer’s noise level has been
improved by 10-15 dB over conventional products.

LV coil
For LV coils above 400 kVA capacity, superior foil conductors are
adopted for winding manufacturing, thus obtaining better ampere-
turn balance and less transverse magnetic flux leakage, and finally to
greatly improve the transformer’s anti-short circuit capability.
By reasonably designing the cooling passage within the coils,
the heat dispersion effect is greatly increased. Thus, the reasonable
design has decreased temperature rise and improved product
overload capability.

HV coil
HV coils are manufactured with superior wire conductors, insulated
and reinforced with fibre glass, and are cast under vacuum and high-
High short-time overload capacity: As the windings of cast resin pressure conditions in Germany’s HOBERS Vacuum Cast Machine,
transformers are encapsulated in resin, the effects of axial and resulting in the best resin penetration and very low partial discharge
radial forces under high current loads are eliminated. Therefore, (partial discharge for 11 kV product < 5pC). An optimised structure is
cast resin transformers can handle short time overloads far adopted for the HV coils, to improve the transformer’s electric field.
better than oil cooled units. Lightning impulse simulation calculation was adopted for the coil model
design, substantially improving the product’s anti-lighting capability.
Crack resistant: Due to historical cracking of cast resin
transformers, the latest technology has introduced glass fibre It should be noted that the choice between a cast resin and oil-
reinforcement in the windings that eliminates cracking due to its cooled transformer is always application-dependent. However,
heating and cooling curves. before deciding, all requirements of the environment and operating
conditions need to be taken into consideration. Today, we live in a
Moisture-resistant: The complete embedding of the world where initial cost is no longer the most important factor, with
transformer winding in resin prevents the penetration of long-term costs on the environment deserving serious contemplation.
moisture. This results in low maintenance and an extended Considering the advantages of cast resin dry-type transformers,
transformer life. and the increasing rate of natural resource extraction – which would
you say is the better choice?
Low noise levels: Due to design flux densities and flexible
winding supports, the noise levels during operation are reduced Contact ArmCoil, Phone 011 763-2351, www.armcoil.co.za
by a considerable amount.

Compact design: By the nature of the design, cast resin
transformers on their own, excluding an enclosure, are more
compact and require less space than oil cooled units.

Sustainable: Using a cast resin transformer contributes to saving
our resources. Its design and operation are considerate of the
environment through:

• A long service life of 30+ years,
• Its low loss levels.
• 90% recyclable transformer materials; meaning less waste.

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