ELECTRICITY IN THE MODERN FACTORY

Evening Star, Issue 19550, 7 May 1927, Page 19

ELECTRICITY IN THE MODERN FACTORY

POWER ADD HEATING

[Written by “ Engineer," for the ‘Evening Star. J

Electricity has already done in the factory what, by the average man, is thought to be miraculous; but in the future it will reveal still greater marvels. Progress proceeds by reaction, and necessity is, indeed, the mother of invention. Defeat in one direction prepares for success in another. There are no straight lines in motion, and the tail of' - movement is a curve backward and forward, tracing a rising spiral. Generally speaking, the first period of the great electric machine age is now with us; progress has been so rapid as to almost dazzle the average man into the belief that' we coujd not possibly go any further, except in minor details. However, the results of inventive scientific research, as being carried out today, might be the means of the . adoption of new ideas on any scale that will be eagerly sought for in the future. To-day a glance over the Press of tjje world in the spheres of economics, .industry, and science indicates a tremendous fermentation and a throwing to the surface of plans and inventions that would have been considered impracticable a few years ago. Human genius has already done that which to the average man is wonderful, but in the future it will reveal still greater marvels amongst the peoples. To attain this great progress elecncity has played a great part, and will do further wonders in the future. Its growth and progress have been so rapid that the business man to-day employs it extensively in his manufacturing concerns, realising that, to keep pace with his future competitors, this great force known as electricity is the class of power that will give him the greatest satisfaction.

Before going too far into this subject we had better have a look at the department’s charges, which will be found to be quite different from private house charges, and, as they are quite simple, a little time spent in the study of them verv often saves many pounds. If at any time anyone is in doubt the department will always oblige by coming to his assistance. To overcome unnecessary loading and allow the department’s plant to maintain a steady load, rules and conditions have been drawn up. After you have perused these you will clearly understand that the department’s policy, boiled down, is: we want you to study us, and we shall study you. Do not bo afraid to communicate with them, as they are there to assist you when in doubt, and I do not know of a single instance where they have failed in their duties.

Here are the ratings:— COMMERCIAL SUPPLY. —Lighting.— (a) Flat rate of 6d per unit. (b) Fivepence per unit until the quantity consumed amounts to 45, multiplied by the consumer’s maximum kva. demand as shown by thermal maximum demand indicator, and Id for all units used in excess of this amount. Alternative rate “b ” is subject to a guaranteed minimum revenue of £ 10s per kva. a year. In the case of lighting in business premises consumers will be charged at the rate which will, in the opinion of the department, be most economical for each consumer, and an adjustment will bo made m the December account if necessary. —Heating.— (a) Twopence per unit until the quantity consumed amounts to 50 multiplied by the consumer’s maximum demand in kva. as shown by a maximum demand indicator, and id per unit for all units used in excess of this amount. The above rate is subject to a minimum guarantee of £4 per kva. year. (b) Flat rate 'of 3d per unit. POWER. —Ordinary Rates. —

(a) For unrestricted supply, 2d per unit for the first 60 units per month per brake horse power installed, or, at the option of either the consumer or the n, per kva. of maximum demand as shown by a maximum demand indicator of tire thermal type; all units used in excess of this amount at one halfpenny per unit. The shove rate is subject to a minimum revenue of 6s per month per h.p. installed, or per kva. measured by the maximum demand indicator in the case of accounts rendered in May, June, July, August, and September only. (b) For consumers who will agree not to use their motors between 3 p.m. and 10 p.m., from April 15 to September 15, 2d per unit for the first 50 units per_ month per brake hoVse power installed, or, at the option of either the consumer or the corporation, per kva. per maximum demand indicator of tho thermal type; all units used in excess of this amount at bne halfpenny per unit. The above rates are subject to a minimum guarantee of 2s 6d per month per h.p. installed, or per kva. measured by the maximum demand indicator in the case of accounts rendered in May, June, July, August, and September only. a For ordinary consumers whose ar working hours are between 10 p.m. and 7.30 a.m., or special rate consumers who wish to work a second shift at intervals during these hours, flat rate of one halfpenny ;.er unit. (d) Consumers with motors _ of 8 h.p. or less may have the option of paying the lighting flat rate of 6d per unit for all units used in case of iiccounts rendered in May, June, July, August, and September only, 2d per unit being charged during the rest of the year. METER RENTS.

Wattmeter rents _ ... os per year Maximum demand indicator rents 10s per year Time switch for restricted supply ... 10s per year Maximum demand indicators are reset in March and September. Meter rents not charged for domestic supply.

By this you will see that the best rating for your power and heat is by the maximum demand. This is quite a different proposition from the household way of charging, which is by the square foot. The maximum demand indicator is an instrument like a thermometer, and the registration is caused by heat. The amount of current passing around the bulb heats a wire strip, which has the same effect on the maximum demand as the heat of the sun would have on a _ thermometer. The thermometer rises and falls, but the maximum demand stops at the highest reading until reset, which is done by tipping. This is the instrument that governs your charges, and therefore should have close attention. The department issued cards to be filled in monthly, so that_the consumer could see at a glance if his charges had increased, but consumers, through not becoming; conversant with the method of marking, failed to take any interest in them, and the system of card marking diea a natural death. _ This again shows what a wonderful faith +he consumer has in electricity, and I would be safe in saying that no other part cf his business receives less attention. I should like to make the consumer realise that by giving the maximum demand his attention pounds could be saved annually, and in some cases the charges could be almost halved. When any part of your plant goes sick, such ns bearings becoming worn, shafts out of line, and many things that cause extra loading, up goes the maximum

demand and up go your charges. Surely au the face of this fact your installation deserves consideration, and instructions should be issued in that direction. ■ „ , , For the of offices and business premises two kinds of heaters are generally used, luminous and convector y fn the luminous type the heat is derived from the glowing filament of a large incandescent lamp. The heat rays from these lamps pass through the air without warming it to any perceptible degree, and when these rays meet with anv solid object that object is wanned, and in its turn heats the air around it. In the convector type the heat is generated by current being passed through high-resistance metallic strips. The air coming in contact with these strips becomes heated and rises. The apparatus is so arranged as to induce coutinual circulation of air, which on entering is cool and on leaving is warm, thus warming all the air in a room by air circulation.

On calculating the size of a radiator necessary to warm a room consideration must be' paid to the shape and height of the room. Broadly speaking, for ordinary living rooms, which are generally square, one tan safely reckon on one watt hour consumption per H cubic feet of air to be warmed. It is not necessary to keep the radiator at full heat. A radiator fixed in a room the capacity of which is in proportion to the above figures will warm the air in that room in about one hour, after which time it will only be necessary to keep the radiator on at half-heat to maintain the room at an even temperature of, say, 63 to 65 degrees. As tno currt'rti supplied is alternating, your motor must bo suitable for this current. These motors are also in two classes, known as squirrel-cage motors and slip-ring motors. _ In the squirrel-cage motor the rotating part contains a winding made up of solid bars connected to two copper rings, one at either end, without any outside connection whatever. These motors are, therefore, extremely simple and are particularly suitable for operation where rough labor only is available. They can, howe/er, start only against a moderate torqu,e equal to one-quarter to one-half of the full load torque, and take nt starting a considerable _ current from the mains, so that special precautions must be taken, as explained before, for the starter. Slip-ring motors have the rotor winding connected to three slip rings, which make it possible to InVrt a resistance in starting up the motors. The torque which these motors develop at starting is a very large one, and can be two or three times the full load torque. The current taken by the motor at starting is almost proportional to the torque. When a motor of tills kind has to start up at long intervals and run for a considerable period arrangements can be fitted to the slip rings to lift the brushes off, thereby reducing the wear of the brushes and of the rings. So far as the running is concerned, both squirrel-cage and slip-ring motors are equally satisfactory. They can deal with a variable load, and the current taken at any time is very nearly proportional to the load. Alternating current motors running light take from the mains a current equal to about one-third of the full load current for the purpose of magnetising their field system. This current, however. does not represent actual consumption of watts, and therefore will not register on the watt metojt, and will not have to bo paid for, except in a very small percentage. The standard alternating current motor is essentially a constant speed machine, the speed being dependent upon the number of poles and the frequency of the supply current. _ The starting and running characteristics of these machines are similar to those of shun* wound continuous current moThere are many types of radiators and motors on the market, which, like other things in your Factory, require serious consideration before installing. They are, like all other lines, good, baa, or indifferent. The motors should be judged by their power factor and efficiency under varying loads. This can only be done under the supervision of nn expert, which would repay you’in the long run. Again I repeat a groat deal could be written on this matter, but we must pass on, and at a later date again return to the subject, as it is most important. One point I should like to stress, and that is that to the man who values study dependability in his machinery, there is no question as to the country of its origin. He demands the British product, for he realises that no engineers the world over can construct machinery of such sterling quality as they. If this bo true of machinery in, general, how much more is it true of electrical motors in particular, where such wonderful progress has been made of rocont years in electrical appliances. Electrical power is undoubtedly one of the greatest boons ever conferred upon mankind. It performs prodigious tasks in transportation, and in keeping the wheels of industry running smoothly, silently, and economically. Now that the eagerly-lookod-for hydro-electric systems are becoming an accomplished fact, many of the laborious tasks of the rural worker will disappear. True, ho has had choice ox oil and gas engines in the past, but bo has naturally looked askance at these means of generating power, by reason of the attendant risks, the difficulty of obtaining fuel, and the cost of operation.

Electricity is brought to the premises. It may be harnessed at any time of the twenty-four hours. A movement of the levers, and the electrical motor is humming immediately, ready and eager to operate the milking machine, the threasher. or the chancutter for the man on the land, the circular saw for the saw-miller, or perform any of the multitudinous tasks where power is needed. Careful supervision is required on all drives, belts, and machines in operation. When installed correctly, electricity shows marked economy in operation. and increases the output, which is due to the steadiness of the drive, and the more perfect method of control. Also, increased safety is made possible and other inherent advantages of the electric drive which have a value far outweighing the economy of the whole system. Electric motors are placed in all sorts of positions, and receive the least consideration of any equipment in the factory. This is brought about by their high efficiency; they are fool-proof, and do not require tbo attention necessary to other methods of driving. In fact, too little attention is often given to the motors, as it is quite a common thing to find them snowed under by all sorts of waste produced by the factory; therefore, the man in charge should have instructions (if efficiency is to be maintained) in their upkeep. Bearing and air gaps require periodical attention, oil wells should be cleaned out and proper lubricant put in The lubricant plays a big part, and I have often found wrong lubricants being used, and have asked the reason why, and been told that this has been advised. All motors when under load throw out a proportion of heat, this .heat is transmitted along the shaft, causing the oil to become less dense. When in this state, instead_ of clinging to the oilrings and lubricating the shaft, it is thrown away from the ring, and the bearing, _ through being starved for want of oil, wears away all too soon, thus causing undue stoppages, and I have seen a breakdown in the windings caused from the above fault. So study your oil. Another cause of unnecessary expense and waste of time until this fault is rectified is shafts out of lino, and it would surprise many manufacturers if they were to get their plant indicated, which is easily done, and see what power is wasted through bad drives. To do this all machinery _ must be in motion, but no production allowed to go on while the test is being taken;

reckon up the loss for a twelve-month, and you will bo surprised. This fact lias been brought homo to many in this citv, and in one place I have before me, 6 li.p. was saved by relmmg and substituting ball bearings against sleeve bearings that bad been in for years. I have illustrated this simply because many people to-day are content to go on as long as the wheels go around, when many savings could bo taking place by the consideration which should bo given when the electric drive is in operation, as all this is a big factor with you maximum demand, and the maximum demand in most factories governs the charges. Very little need be said on heating, further than, again study your rating as I have copied it for you, find out which is most suitable to your requirements, and ask to be put on that rating. If you will refer to my previous article about the placing of lights, this also applies to the office and factory. The whole subject is a vast one, and as I am compelled to boil it all down, I trust that I have not confined my suhjost in too small a space, and that those who have the welfare of tbeir home, office, or factory at heart have been able to grip the theme of the article, and become more conversant with the subject of My_ labors will not then have been in vain.

My next article will be ‘ Tips to be Observed,’ and general advice on electrical matters.