February 2014
MODERN MINING
17
COVER STORY
by the
downturn in mining
The internals of a dry type
transformer showing coil
construction.
Kopex’s well-equipped
factory has a floor area
of 5 000 m
2
.
sub-station skid for use in an open pit to supply
power to draglines which weigh up to 50 tons.
“Most hard-rock mines in South Africa use
oil-cooled transformers but in underground
coal mining the dry – i.e. air-cooled – trans-
former reigns supreme,” says Roets. “These
units can cost up to three times as much as oil-
cooled transformers but their use is mandatory
for safety reasons.” He notes that flameproof-
ing adds substantially to the already wide price
differential. “A normal transformer uses 5 mm
steel,” he explains. “With flameproof units, this
5 mm can become 50 mm, resulting in addi-
tional cost and, of course, a much heavier unit.”
According to Roets, the Kopex transformer
can be seen as a ‘Rolls Royce’ product. “It is
built by hand to the customer’s exact specifi-
cation,” he says. “We don’t use machines and
robots, as many overseas manufacturers do,
because this approach generally results in infe-
rior quality. Of course, if you manufacture by
hand, you need skilled, experienced employees
– your workforce is absolutely crucial. We have
these people and indeed many of them have
been with us for over 10 years. We also have
a full engineering and R&D capability and the
depth of expertise in this department is prob-
ably unmatched in South Africa.”
Kopex’s transformers are subject to what is
known as ‘type testing’ in which new designs
