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11/11/2005
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Tom Shelley reports on an inexpensive device that both reduces electricity bills and improves power quality
Tom Shelley reports on an inexpensive device that both reduces electricity bills and improves power quality
Money can be saved and power quality improved without major expenditure by making use of a device that is at the same time a three phase choke connected in series with the mains supply, a phase balancing transformer and a harmonic trap.
The effect of the choke is to introduce reactance into the supply line and reduce supply voltage to systems, reducing power consumption and also ironing out voltage spikes. While it does not perform as well as electronic semiconductor device based power conditioning systems, it appears to do well enough to please an increasing number of users without incurring excessive cost.
The powerPerfector is the invention of Japanese engineer Kunio Shimazu, who developed it in 1993. Average voltage supply in the UK is still around 242V while systems are generally optimised for 230V. The main effect of the extra voltage is to waste energy It is also worth noting that light bulbs designed to last 1,000h at 230V can only be expected to last 550h at 240V. Before installing a unit, the first thing to do is to establish what range the mains supply voltage actually covers, and what voltage and what power level is actually required, after which a suitable unit can be chosen to drop the mains voltage accordingly.
This could, of course, equally be achieved by installing a suitable, conventional, three phase reactor choke in the mains supply. The powerPerfector, however, also includes two additional tweaks in the form of secondary transformer windings. One set is connected in a star configuration to the other phases to from an internal floating neutral thus providing a balanced output voltage. The other set is a connected in a closed delta configuration in order to eliminate harmonic currents in the supply. It is possible to change the effective reactance of the three phase choke by changing the tap connections on the voltage balancing windings.
Satisfied customers are said to include Tesco, which has been trying units at four sites where they are said to have achieved power savings of 11 per cent to 29.4 per cent. Buckinghamshire County Council has applied the technology to reduce the voltage supplied to its New County Offices in Aylesbury by 8 per cent. It is said that as a result, overall energy consumption has been reduced by 13.1 per cent, maximum demand by 10 per cent, peak harmonic distortion by 12 per cent, and current in neutral by 7 per cent. Annual saving is £12,000 giving a 25 month payback and a 48 per cent return on investment. At a press conference to promote the technology, Martin Illingworth of the Land Registry described how the units had reduced the cost of power supplied to 26 major buildings and eliminated computer crashes caused by power spikes.
If the user application requires mains voltage to be supplied at a precisely defined level, however, the powerPerfector will not do this and a semiconductor device controlled system as supplied by the major global electrical engineering companies should be sought.
powerPerfector
Pointers
* Unit takes the form of a three phase mains choke, imposing a reactance in the mains supply and reducing effective supply voltage
* It also includes additional secondary windings to provide a more balanced output voltage and trap harmonics
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Author
Tom Shelley
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