June 5, 1914. THE COLLIERY GUARDIAN. 1241 280 revolutions per minute for continuous running, and has ample overload capacity for the winding service shown in figs. 13 and 14. The consumption of energy is seven units per wind, and as the shaft horse power hours (assuming a winding depth of 450 yds.) are 4’8, the efficiency from electrical horse power input to shaft horse power is 51 per cent. The controllers for oper- ating the winding motors are of the liquid type, and consist of a large tank containing an upper and a Imver compartment. The liquid is pumped continuously, by a small motor-driven centrifugal pump, from the lower tank into the upper tank, in which the contact plates are fixed, and overflows over a weir gate back into the Fig. 13. Brake-horsepower Time Diagram. KLTRE8 TlRQUE 24. OOOp HORSEPOWER 1,600 — Fig-. 15.—Diagram of Connexions of Electric Winding-engine and Auxiliaries. POWER-FACTOR INDICATOR INDICATING WATTMETER! OVERLOAD COILS RESISTANCES joVERipAO COILS ISOLATING PLUGS IINUTE 750 REVOLUTIONS PER MINUTE SERIES TRANSFORMER] 2W'/2U5 AMPERES g ■LIGHTING CIRCUIT SHUNT .TRANSFORMERS 3,000/1'00 VOLTS COMPRESSOR-MOTOR, 7 HORSEPOWER. 440 VOLTS . THREE-PHASE. 750 REVOLUTIONS PER MINUTE1 2,900 VOLTS, 40 PERIODS, THREE-PHASE BUS-BAR6 ISOLATING PLUGS W-l OIL-SWITCH KJq-ra/ SE BRAKE SOLENOID rsWrJc'H OPERATED BY •ALLHb SOLENOID CORE the same driver’s control lever, are of the oil-immersed type, and are fitted with auxiliary sparking contacts. These switches are the only parts of the controller that require attention. It is important that they should be amply proportioned and frequently examined; and at Blackhall Colliery they are examined once every day. The oil tanks are fitted with screw raising and lowering gear, and can easily be lowered for inspection of the switch contacts. The daily inspection and cleaning of the switches, therefore, does not take more than 15 minutes. The quality of the oil is important, but even with the best of oils a certain amount of carbonisation will take place. The carbon deposit does not, however, Fig. 14.—Torque-turn Diagram. main supply to the winders in each engine house are of the cast iron mining type, and are fitted, as pre- viously mentioned, in the driver’s cabin. The switches are oil-immersed, and fitted with ammeters and volt- meters, no-volt and overload trips, and insulating plugs. The depth indicator is of the makers’ standard vertical design, and is provided with the necessary tripping gear for operating the emergency brakes, and for opening the main circuit breaker in the various emergencies pre- viously detailed. A main ammeter and voltmeter of the illuminated dial type is fitted in full view of the driver. A Karlik tachograph is also installed. When the type of electric winding engine to be installed at this colliery was considered, it was found that if a cylindro-conical drum were fitted, the peak loads on the driving motor would not exceed, with the duty required, 1,500-brake horse power. As the power company undertook to deal with peak loads of this amount, without requiring a balancing set to be fitted, it was decided to adopt, for the sake of simplicity, the type of winder described, driven direct by a three-phase motor, and operated at the full supply voltage of 2,900. By adopting gear drive, as against coupling the motor direct on to the drum shaft, a motor of much smaller size, and having a better power factor and efficiency, could be employed. As already mentioned, the gearing fitted has proved entirely satisfactory. The use of a direct current motor, with Ward-Leonard or other type of control, was considered. These systems, however, involve the running of a motor generator or rotary con- verter plant which has often to be kept running at times when the main winder is operating only infre- quently. The losses in the auxiliary plant are practi- cally constant, and when they were taken into account, it was found in this case that any saving in the energy consumption due to reduced rheostatic losses at starting by the adoption of Ward-Leonard control more than dis- appeared when the consumption of energy was taken over, say, a week of normal operation. It has also to be remembered that the auxiliary plant, besides requir- ing attention, increases the liability to breakdown. Moreover, the cost of a Ward-Leonard equipment for this work was found to be about 25 per cent, greater than the type fitted. It may be pointed out, however, that each case should be considered on its merits, as if the power company had been unable to deal with the peak loads obtained, or if the conditions had required the installation of a larger winding engine than that described, a different type of plant might have been found necessary. At present the writers believe that these are the biggest geared winding engines in the country, although there are several of the same type, but of greater capacity, in South Africa. Fig. 15 shows the diagram of connections of the winding gear and auxiliaries. Switch Gear in Power House.—The alternating cur- rent switch gear in the power house is grouped into two switchboards, both of the wardrobe type, consisting of cells constructed of planished sheet steel, with angle iron framing. The high-tension board is divided into two duplicate portions, connected together through a busbar coupling switch. Each half of the board is fed by a separate feeder from the sub-station, and controls half of the plant, -by which means certainty of supply is assured in the case of a fault on either feeder or busbar Pt Figs. 16, 17, and 18.—Lay-out of Underground Pump House. 1 containing tank. The height of the liquid in the upper tank, and consequently the depth of immersion of the contact plates, is controlled by the raising or lowering of the weir gate, which is operated by the driver’s con- trol lever. A valve is fitted in the pump delivery, and, by adjusting this, the maximum rate of acceleration which the driver can employ when operating the winder may be fixed. The forced circulation of the liquid by the pump prevents any boiling of the liquid by the heavy rotor-current of the motor passing through the contact plates. The controllers are of ample capacity, both for the ordinary winding service and for occasional inspection trips, at a speed of approximately 1 ft. per second. The reversing switches, which are operated by give trouble, unless allowed to accumulate, and can easily be removed from the oil by mechanical filtering. A suitable and inexpensive filter, which was obtained from the winding engine makers, has been installed in each engine room. It is only necessary once a fortnight to empty the switch tanks into the filter, and to fill them up again with clean oil from the filter, the same oil being used over and over again. The sparking contacts are examined, and, if necessary, dressed up with a file while the oil is being renewed. So far, renewal of these con- tacts has not proved a serious item. Generally, it may be stated that the control of the drum by the apparatus described has proved very satisfactory in practice. The high tension switch gear pillars controlling the section, and maximum flexibility is attained for clean- ing, overhauling, and running repairs. This switch- board consists of two feeder panels, two winder panels, two fan motor panels, two compressor panels, two shaft cable panels, two transformer panels, two motor generator panels, and one busbar coupling switch—15 panels in all. Continuous service with respect to the low tension board is not so important, as it can be made dead at regular intervals. In consequence of this, the busbars are made continuous, no sectionalising switch being provided. This board is fed from the high-tension board previously mentioned through two 200 kilovolt- ampere three-phase Siemens transformers, of the oil-