Gambar halaman

increase the power-factor to 100 kilowatts from the lower to the higher power-factor. The energy component is 100 kilowatts; at 80-per cent power-factor the total kilovolt-amperes is 125 and the wattless component is 76 kilovolt-amperes. With the same energy component and 95-per cent power-factor the total kilovolt-amperes is 105 and the wattless component 34 kilovolt-amperes. The difference, which is the required capacity of the synchronous condenser, is 42 kilovolt-amperes, as shown by the table. In Table II take the same power-factors. In this case the table is based on a total load of 100 kilovolt-amperes. Then at 80-per cent power-factor the energy component is 80 kilowatts and the wattless component is 60 kilovolt-amperes. With the same energy load of 80 kilowatts (since in practice it is the energy load that remains constant with change of powerfactor) and 95-per cent power-factor, the total load is 84.2 kilovolt-amperes and the wattless component is 26 kilovolt-amperes. The required capacity of the synchronous condenser is 34 kilovolt-amperes, as shown by the table.


CONDENSER The synchronous condenser has been considered, up to this point, entirely in its relation to the system. There are various

. distinctive qualifications that it should possess, which will now be discussed.

The synchronous condenser operates at practically zero power-factor, leading, the only energy component being. its losses. It should, therefore, be rated to carry its normal current at normal voltage and at zero power-factor with the desired temperature rise. Operating at zero power-factor, leading, it will require a large increase in field current beyond the no-load field current. The necessary margin in exciting voltage should, therefore, be provided.

There being no energy load, the speed may be chosen to suit the electrical conditions. At first thought it would seem that the speed should be as high as the frequency will permit. The most favorable speed, however, is lower than this. On account of the high field current required, caused by the zero powerfactor, the field windings become one of the first limitations in the design. A large field loss requires, relatively, a large number

[ocr errors]

of poles to dissipate it, and the speed must be reduced in order to obtain the necessary number of poles.

The conditions of operation of the synchronous condenser are favorable to starting directly with alternating current in the armature winding. Whether or not this method can be used is determined almost entirely by the drop in voltage in the system caused by this method. This is determined largely by the relation between the size of the synchronous condenser and the generating capacity. If the capacity of the generators is several times the capacity of the condenser and exact voltage regulation is not important, there should be no difficulty in starting the synchronous condenser direct. When so started it will require from one to one and one-quarter times its rated kilovolt-amperes for starting. This starting current will have a power-factor of about 30 per cent. If the line conditions are such that this starting current is not permissible an induction starting motor

may be used.

The electrical proportions and operating conditions require good damping characteristics to prevent hunting. The necessary damping can in some cases be obtained by using a short-circuited cage winding on the synchronous condenser revolving part similar to the cage winding of an induction motor. When this cage winding is used for its damping properties it should be made of relatively low resistance. This is antagonistic to low starting current. That is, if good dampers are provided the starting performance must be sacrificed. In most cases, however, it is better to insure good operating characteristics by using lowresistance dampers and to let the starting performance suffer to that extent.

The PRESIDENT: The paper is open for discussion. If no one desires to discuss the paper, or ask Mr. Newbury any questions regarding his excellent paper, we will proceed to the next paper on the programme. Mr. Ferguson has asked that his discussion be deferred. He is waiting for some further data from Chicago, which is expected to arrive very soon.

We will now proceed to the presentation of the Question Box, edited by Mr. Paul Lüpke. Mr. Spencer will present the Question Box for Mr. Lüpke.

MR. Paur SPENCER (Philadelphia, Pa.): The following is the introduction to the Question Box, as prepared by Mr. Lüpke. The Question Box itself, I understand, will be ready toward the end of the week:

In the introduction to last year's issue I ventured to suggest that perhaps some better way might be found to carry on the work the Question Box is intended to cover. Within the past month a circular issued by the American Gas Institute has been brought to my notice, and I am free to express as my opinion that the plan outlined therein is superior in some ways to our present method of handling this subject.

Briefly, this plan is as follows:

A Bureau of Information is formed, composed of six members, among whom the different subjects to be covered are divided. The method of proceeding is given in this paragraph quoted from the circular:

"The members are invited to send to the secretary all questions to which answers by the Bureau are desired. The Bureau will not attempt to do the work of a consulting gas engineer. It will in many cases rather attempt to indicate methods of solution than actually solve the problem given. Where satisfactory answers already exist to questions asked, the questioner will be directed to these answers. Where the questions are incapable of a positive answer, the questioner will be so told. Where the matter is plainly one for a consulting gas engineer, the questioner will be advised to employ one.

“All questions and answers that may be deemed of value to the membership in general will be recommended by the Bureau to the Directors of the Institute for publication in the Proceedings."

It is entirely feasible to embody in this plan a feature that would admit of having all questions of policy or opinion submitted to all members, so that this valuable feature of the present plan of the Question Box would not be lost.

In presenting the present volume I must once more pay due tribute to the tireless co-operation of Miss Harriet Billings, our assistant secretary, and I must again express my thanks to Mr. E. C. Stahl, Jr., and Mr. Clarence A. Hutchings, for their efficient help.

[The complete Question Bor will be found in Volume II of the Proceedings.-EDITOR.]

THE PRESIDENT: The report on the Question Box may be referred to at any time during the convention. Mr. Lüpke practically recommends, as I understand it, that we have a standing committee during the year, to whom members of the association desiring information may appeal for such information, and either of the committee's personal knowledge, or through information obtained by correspondence with other members, the applicant for information may be immediately informed upon the point concerning which he desires to be advised; and that the question and answer will afterward be included and presented as part of the Question Box of the year. This would seem to be an interesting and desirable change, and it has occurred to Mr. Lüpke and Mr. Spencer that perhaps you would like to have an opportunity of discussing it.

DISCUSSION Mr. H. T. HARTMAN (Philadelphia, Pa.): I think the suggestion, if carried out, would probably add very greatly to the efficiency of the Question Box. There is no doubt that men could be selected by this association, each a specialist in his own line, who could give, possibly, very much better answers than the average that we get in our Question Box. I think, however, that this Question Box is one of the most valuable features of our association work, in that it gives every man an opportunity to be of some use to the association. In any association of this kind there is entirely too much of a tendency for all the work to devolve upon some half-dozen or dozen men. If you look over the papers presented, and the list of officers, for the last five or six years you will be surprised to find how few men out of the total of this great association are represented. Every one of the members owes a duty to the association. He can not expect to go along and profit by the work of other men unless he contributes something toward it himself. I believe we owe this duty to the association. It does not come in the form of a demand, but is offered as an opportunity. Each one of us has had special experiences, possibly, that others of us have not had. Each member has the chance through the medium of this Question Box to contribute that information.

Another valuable feature of allowing each man to answer, and expecting each man to answer, is the fact that you get so many points of view upon the same question. Oftentimes the

questions as asked are quite indefinite, and possibly of half a dozen answers only two or three will strike what the questioner wishes to know. Still another point, where I think the Question Box in its present form is of value, is this: Ours is a business into which young men are constantly entering, and they increase in capacity and experience very rapidly indeed. We ought to have some way of finding out the men who have that knowledge and who are willing to do the work. There is plenty of work to be done; we have got to find the men to do it.

Mr. Douglass BURNETT (Baltimore, Md.): I am entirely in accord with the suggestions that have been made on this occasion and, I believe, previously by Mr. Lüpke. There is not the slightest doubt that there are many inquiries in the Question Box that have already been answered again and again, and any step that we may take toward standardizing our information is a good one.

MR. SPENCER: I think that Mr. Lüpke's recommendations should be given careful consideration. Certainly the hard and intelligent work that he has done in the past two years in connection with the Question Box gives his recommendation great weight. As I conceive it, he believes that in its present form the Question Box is not serving the best interests of the association. I think that the present method of conducting the Question Box is unsatisfactory for two reasons: First, on account of the great amount of labor that it devolves upon one man. It hardly seems right for the association to put upon one man the great amount of work required. The second reason is that the answers are published so long after they are sent in that the matter is no longer alive—assuming that the question when received was really a live question, and not a forced question. It seems to me that a committee—not to answer questions, but to obtain answers by directing the question into the correct channels for proper answering—would serve to lighten the work now devolving upon one man, and would serve also to obtain better results, as well as to provide for the immediate sending of the answer to the person who asked the question.

If it is in order, therefore, I will make a motion that the question of the best method of handling the Question Box be left to the incoming administration, but with the recommendation that a method be adopted that will provide for supplying

« SebelumnyaLanjutkan »