Figs. 167 and 168 and Table XXVIII. show the effects of governing with an electrical governor.

It will be noticed that the centrifugal governor increases the speed with diminishing load and reduces the speed with increasing load, while the action of the electrical governor is the reverse.

The low steam consumption obtained with the Elberfeld machine has since been beaten by more than one large turbine constructed by Messrs. C. A. Parsons and Co.

CHAPTER XII.

SOME OTHER STEAM TURBINES.

Westinghouse-Parsons Steam Turbines, built by the Westinghouse Machine Company of Pittsburg, U.S.A., and by the British Westinghouse Electric & Manufacturing Company, Limited, of Manchester, are of the same nature as the turbines built by Messrs. C. A. Parsons & Co.; but it is convenient to consider them here.

In 1896 the Westinghouse Machine Company acquired the rights to manufacture Parsons steam turbines in the United States, and since then have built a considerable number. Figs 169, 170, and 171 show a 500-H.P. steam turbine constructed by this company and coupled to a 300-K.W. bipolar, two-phase alternator. The author is indebted for these views to an article by Mr. B. Harding in the Engineering Pip, New York. The steam inlet can be seen in the plan and end elevation, and the governor-valve close beside it is seen in the former figure. The governor is situated over the low pressure end of the turbine. The oil-pump for supplying lubricant under pressure can also be seen at this end; it is daven by a worm-wheel gearing with a worm situated at the compling learn the turbine and alternator shafts. mbine is of the parallel flow type, and the steam in its passage along the wideg vlinder from the high-pressure end to the

The

exhaust end acts in succession on 58 rings of blades, and is expanded about ninety-six-fold, that is from 120 to 125 lbs. pressure above atmosphere down to 1 to 1 lbs. abs. Each blade contributes at full load to the extent of about 1 oz. to the force required to turn the turbine spindle. The speed is 3600 revolutions per minute, the voltage 440, and the alternations per second 120.

The turbine and alternator are carried on the same bedplate, and this rests without holding-down bolts on brick piers, which are merely sufficient to carry the weight of the machine. The complete machine-turbine, alternator, and bed-plateweighs about 25,000 lbs. The principal dimensions are given in the figures.

Plate XIX. illustrates the engine-room of the Westinghouse Air Brake Company at Wilmerding, Pa., U.S.A., in which four of these turbo-alternators are installed, and supply electric energy for light and power.

A by-pass valve is provided on each turbine, and this is used when the turbine has to work at overload or when the boilerpressure is reduced or the condenser vacuum impaired. The by-pass valve admits high-pressure steam to an intermediate part of the turbine casing. This, of course, reduces the efficiency. The effect of opening the valve can be well seen in Fig. 171A. Here the upper curve indicates the steam consumption of the turbine when run non-condensing. The by-pass valve has been opened at a little over 200 E.H.P. The lower curve shows the steam-consumption of the turbine when exhausting into a condenser.

A test was recently made by Professor Robb, of the Electrical Engineering Rensselaer Polytechnic Institute, on a Westinghouse-Parsons steam turbine constructed by the