Sparks Electrical News September 2019

CONTRACTORS’ CORNER

5

WORKING KNOWLEDGE WITH TERRY MACKENZIE HOY

CLEAN LINE AND HARMONICS

HIGH POWER LOW VIBRATION ROTARY HAMMER The electricity distribution system in the buildings had not been designed for air-conditioning loads. Thus, sometimes when the A/C unit started, the voltage dip caused the lights to flicker and the word processors and computers to reset. This was very tedious. Soon a belief was spread (by the interior designers, who knew nothing about electricity) that all computers had to be fed from a ‘clean line’ which was an electrical circuit separate from the circuit that fed an A/C unit. Now, N obody who is not middle aged will recognise the business offices of times gone by. Back in the day (as they say) there were no ‘open plan’ offices – there were individual offices, each with a door. Managers got a single big office with plas- tered brick walls. Less important staff had cubicles which were ¾ height, normally with timber and glass partitions. There was an open area called the ‘typ- ing pool’ where typists (all women) typed out letters. There were no computers until about 1980. When computers did arrive they were in two forms: IBM computers or ‘IBM Compatible computers’ using Microsoft software and Apple computers. Both types came with word processing software. The MS-Dos word processing software was the worst software on the planet. Soon word processors appeared. Not really computers, they were a huge step forward – they had spell checking functions and documents were easy to modify and ‘cut and paste’. There was, for some reason, a generally held belief that word processors and computers had to be in an air-conditioned environment. Perhaps the rumours were generated by the office staff, since at the time, air-conditioning was very rare. In any event, installation of computers equalled installation of air-conditioning units in the form of wall mounted units (‘window rattlers’) or split units. MAKITA has produced one of the world’s largest ranges of 18 V power tools, and through its continu- ous research and development is constantly pro- ducing innovative new and exciting tools to enhance its range. Makita’s latest offering to its twin battery range is the DHR400ZK. Powered by two 18 V LXT batteries, installed in series to supply energy to the powerful 36 V dc motor drive system, these twin battery tools offer great versatility, as they utilise your existing 18 V battery and charger system. Not only do the tools compete head-to-head with their corded counterparts but they are a significantly more affordable option than having to purchase a 36 V tool and batteries. The New DHR400ZK Twin Battery Rotary Hammer has a two-mode operation with an SDS- Max shank – rotary drilling with hammer action and hammer action only – ensuring easy operation and handling and providing 8.0 Joules of impact energy. The built-in LED light ensures greater accuracy in poor light conditions. Measuring 473 mm in length, the DHR400ZK has a 40 mm capacity in concrete with a TCT bit and a 105 mm with a core bit. It features a no load speed of 250-500 r/min and the brushless motor delivers 1450-2900 blows per minute. Operator comfort and more control during operation are ensured as it features Anti-Vibration Technology (AVT) for extra comfort and an unrivalled low level of vibration.

Since ‘harmonics’ are a measure of the distortion of a voltage waveform and, since such distortion can only be caused by very large electrical loads, this whole concept was ditch water from beginning to end. However, soon the demand rose for ‘in line harmonic filters’ to end the ‘blue screen of death’. The fact that this patently didn’t happen worried nobody (the ‘blue screen of death’ lasted until Windows 98 – see https://www.youtube.com/watch?v=IW7Rqwwth84). What I learned from it all was that it is not necessary to admit blame and fix a software problem – it is far better to blame something else and then sell the client an unnecessary item to fix it. Sadly, this still happens today, but I thought I should tell you where it all began, back in the day.

moment the computer would crash and the screen turned blue. The computer suppliers refused to accept that this was a software problem (which it was) but hinted darkly that it was all because the power supply was full of ‘harmonics’. None of the computer people actually knew what a harmonic was and, if questioned, would hint darkly about some manevolent electrical wave which would infest and destroy a computer programmed with Windows 3.1. Most interestingly, a persona was given to harmonic currents: a USA writer referred to them as ‘rogue electrical currents and a UK writer wrote that “in these modern times we have to accept that mankind has misused the gift of electricity and is now being punished with the consequences of this...”

since electricity travels at 100 m per microsecond, the voltage at one point was going to be the same as at the distribution board busbars if the conductor lengths were less than 30 m. So the ‘clean line’ was a non solution to a real problem. The electrical contractors made good money installing all the ‘clean line’ circuits. Things moved on. Microsoft produced Windows 1. It was terrible, slower than a sloth on dope. Then Windows 2. Marginally faster. It was rumoured that Windows 2 had ‘Dungeons and Dragons’ running in the background to slow it down. A suitable software purchase got rid of it and things speeded up, from ‘glacial’ to ‘very slow’. Then came Windows 3.1. Just fast enough. But, free with the software, came the ‘blue screen of death’. At any given

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SEPTEMBER 2019 SPARKS ELECTRICAL NEWS