ponent, in which case the generator need have a rating of only 1200 kilovolt-amperes at 100 per cent power-factor, but a 1220kv-ampere synchronous condenser must be installed in addition. In the first case there is a total generating capacity of 1710 kilovolt-amperes in one unit, and in the second case, of 2420 kilovoltamperes in two units. Obviously, if the speed of the generators is high, so that the cost per kilowatt is no greater than with the synchronous condenser, the plan involving the synchronous condenser will be the more expensive. This is somewhat modified, however, by the fact that, due to the different operating conditions in the generator and synchronous condenser, the latter can be built with approximately 30 per cent less material per kilowatt than the generator. On the other hand, if the generator is operated at slow speed, say 100 r.p.m., it is evident that considerable saving can be effected by making the synchronous condenser of relatively high speed, say 900 r.p.m. This possible difference in speeds, together with the smaller weight per kilowatt of the synchronous condenser, will in some cases make the plan involving the synchronous condenser less expensive than the larger generator. Under the particular conditions of speed and load used above the 1710-kv-ampere, 100-r.p.m. generator will cost practically the same as the 1200-kv-ampere, 100-r.p.m. generator and the 1220-kv-ampere, 900-r.p.m. synchronous condenser. In favor of the synchronous condenser proposition there is also the possible saving in transformers and feeders and the improved regulation. This is by no means a complete comparison; the switchboard, buildings, attendance, and many other points must be considered; but it indicates that the synchronous condenser at least deserves consideration. Under some conditions the comparison will be more in favor of the synchronous condenser if the power-factor is raised to only 90 per cent instead of 100 per cent. It will be noted, in one of the previous examples, that the rating of the synchronous condenser is 1220 kilovolt-amperes to raise the power-factor to 100 per cent, while it is only 585 kilovolt-amperes, or less than half, to raise it to 90 per cent. Using the same data as in the previous paragraph, the rating of the generator should be 1330 kilovoltamperes at 90-per cent power-factor and the rating of the synchronous condenser should be 585 kilovolt-amperes in order to raise the power-factor to 90 per cent. The cost of these two units, at 100 r.p.m. and 900 r.p.m., will be about 5 per cent less than the cost of the 1710-kv-ampere, 100-r.p.m. generator. There is, however, to offset this 5 per cent gain in cost of generating apparatus, a smaller gain in feeder and transformer cost and considerably less improvement in regulation. There is another condition under which the use of synchronous condensers may be justified by decreased investment. This is in cases where a large proportion of the investment is in transformers and feeders. The synchronous condenser not only relieves the generators of the magnetizing current but relieves the feeders and intermediate transforming apparatus. That is, with synchronous condensers, the greater part of the electrical apparatus can be of smaller kilovolt-ampere capacity than when all of the system operates at low power-factor. In cases where the transmission and transforming apparatus form a large proportion of the total electrical apparatus the saving in this part of the system alone may easily pay for the synchronous condensers. This assumes that the synchronous condenser is located as near the cause of the low power-factor as possible, so as to eliminate the magnetizing current from as much of the circuit as possible. The ideal condition is to divide the synchronous-condenser capacity into a number of units distributed throughout the system at the various centres of inductive load. In cases where high-speed generators, such as steam-turbine units, are used, the speed of the synchronous condensers would probably be lower than the speed of the generators. Again, in other cases, with short transmission distances, the saving in feeders may be relatively small. Under these circumstances the use of synchronous condensers would not usually be justified. When low power-factor will prevail and synchronous condensers are not used the size of the generators and other electrical apparatus, in every case, should be increased to take care of the necessary magnetizing current, so that the rating of the engines and generators will be proportionately the same. A very valuable property of the synchronous condenser will merely be referred to. By means of it the voltage at any point of the system where it may be installed can be maintained constant within certain limits. That is, the synchronous condenser will act as a voltage regulator. This requires that the synchronous con denser be sufficiently large, in proportion to the inductive load, to more than supply the magnetizing current so that the current between the synchronous condenser and the generator will be leading. By varying the field current of the synchronous condenser the voltage at the condenser will be varied, provided there is reactance in the circuit. The field current may be varied automatically, to maintain constant voltage, by a Tirrill regulator. This is very similar to the compounding action of compoundwound rotary converters. In laying out a new system, or a new feeder circuit or substation in an old system, in which it is proposed to raise the power-factor by synchronous condensers, difficulty will usually be experienced in estimating the probable power-factor of the new circuit. In such cases the following approximate figures for typical installations may be of service: It is useful to remember that transformers and induction motors take a constant magnetizing current from the circuit, as long as the voltage is constant, independent of their energy load. This may be considered the total wattless component, neglecting leakage. The ratio of their magnetizing component to the rating. of the apparatus is reasonably constant. In induction motors this magnetizing component in kilovolt-amperes averages 30 per cent of the horse-power rating of the motor. In transformers the magnetizing component averages 4 per cent of the kilovolt ampere rating of the transformer. For example, if there is a connected load of 500 horse-power in induction motors the constant wattless component of the induction motor load will be 30 per cent of 500 or 150 kilovolt-amperes. This same wattless TABLE I-KW. Table showing K.V.A. capacity of Synchronous Condenser required to bring 100 K.W from one Power Factor (vertical line) to a higher Power Factor Use this table where load to be compensated is measured by Wattmeter component will be present whether the motors are running with no load or with full load. In certain cases this fact gives a convenient approximate means for estimating the wattless component and the consequent synchronous condenser rating. For purposes of calculation the tables (pages 94 and 95) wil be found convenient. The form of the tables is due to Mr. P. M. Lincoln. The two tables differ only in being worked out for kilowatts in one case and for kilovolt-amperes in the other. They TABLE II-K.V.A. Table showing K.V.A. capacity of Synchronous Condenser required to bring 100 K.V.A.from one Power Factor (vertical line) to a higher Power Factor Use this table where load to be compensated is measured by Ammeter and can be best explained by showing the method of calculation in each case. In Table I, take 80-per cent power-factor (vertical line) to be raised to 95-per cent power-factor (horizontal line). According to the table it will require 42 kilovolt-amperes to |