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Power electrical systems – progress
over time
H du Preez, Consultant
Power savings in transformers and motors is an area where there
have been a number of improvements in the past few decades –
with room for more. Various figures are quotedwhen the equipment
that uses the most electricity is considered. It is said that between
60 and 70% of the total electricity generated is used by electric
motors in some form or other.
A
s most of the power used in the country is generated in par-
ticular areas, a distribution system is required – which means
transformers and transmission lines.
South Africa’s power is predominantly generated by coal – causing
CO
2
emissions that pollute the atmosphere. Saving electricity actually
reduces pollution. Alternative environmentally-friendly generation
systems such as solar, wind, wave and hydro also come with their
particular problems and limitations.
At the turn of the 20
th
century, 1903 and onwards, electricity was
in its infancy with direct current (dc) systems and research into alter-
nating current (ac) just beginning. Dc motors and dc generators were
Figure 1: Ring Dynamo.
Figure 2: Early dc machine.
the norm. Convenience rather than efficiency was the consideration
– light at the turning on of a switch and power away from the water
wheel or steam engine. The incandescent lamp comes from this era.
When ac power started to make its mark, it was realised that pow-
er could be saved; for example, an ac arc lamp requiring 8 Amps (A),
30 Volts (V) and 240Watts (W) but with a 110 V supply, a resistor would
be connected in series; the power in the resistor would be 640 W
wasted power until a choke coil was developed using a coil wound
over an iron core, dropping the voltage with a much smaller power loss.
This system obviously only works when an ac system is employed.
As we progressed through the 20
th
century, technology and ma-
terials advanced to improve efficiency and reduce wasteful systems.
Materials:
Materials have been improved and with better use and
design, savings are realised.
Electrical steels:
The attraction of flux magnification and its
dividend of force control was central to early machine design, but as
the electrical industry grew, the spotlight turned to energy efficiency.
A need for energy, both real and perceived, has been the driver of
electrical innovation for well over a century. Whereas much can be
done to optimise what we already have, the opportunities (especially
in Africa) are driving a new wave of innovation. To appreciate this, it is
important to review our past.
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ENERGY EFFICIENCY MADE SIMPLE 2015