US2057159A - Track shunting apparatus - Google Patents

Description

B. E. o HAGAN TRACK SHUNTING APPARATUS j Oct. 13, 1936.

Filed June 16, 1933- INVENZ'OR fimnand EOZ/agazz BY QJKW HIS ATTORNEY Patented Oct. 13, 1936 UNITED STATES PATENT OFFICE 2,057,159". I TRACK SHUNTING A PPARA TUS Bernard E. OHagan, Swissvale, .Pa., assignor to The UnionSwitch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application June is, 1933,- Serial No. 676,025

2 Claims. (o1. '246-34) My invention relates to track shunting apparatus of the type involving means carried on a vehicle for applying a potential to the rail surface for disrupting the resistance film formed on 5 such surface and thereby decreasing the rail contact resistance.

The present invention is an improvement on the apparatus described and claimed in an application for Letters Patent of .the. United States, Serial No. 644,180, filed by me on November 25, 1932, for Track shunting apparatus.

One object of my invention is the provision of means for increasing the open circuit secondary voltage of the transformer which applies po- 15 tential to the rail surface, without increasing the short circuit secondary current beyond the desired amount.

I will described one form of track shunting apparatus embodying my invention, and will 20 then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a diagrammatic view showing one form of track shunting apparatus embodying my invention.

25 Fig. 2 is a vector diagram illustrating the electrical characteristics of the apparatus shown in Fig. 1.

Referring first to Fig. 1 of the drawing, the reference characters R and R. designate the 0 track rails of a stretch of railway track, which rails are divided by insulated joints to form a section D-E. This section is provided with a track circuit including a track relay F connected across the rails at one end of the section, 35 and a transformer H the secondary of which is connected across the rails at the other end of the section through a current-limiting impedance 5. The primary of transformer H is constantly supplied with alternating current from a 4,0 suitable source, the terminals of which are designated Y and Z.

The remaining apparatus illustrated in Fig. 1 is arranged to be carried on a rail vehicle. The reference character MG designates a motor gen- 45 erator set comprising an alternating current generator G driven by a motor M which receives current from a battery B. A transformer T has a primary winding P supplied with current from the generator G, and two secondary windings 50 S and S having substantially the same number of turns. Winding S is connected across the two rails of the track by means of suitable contact shoes I and 4, whereas winding S is connected across the rails by means of contact 55 shoes 3 and 2. The polarities of the two secondary windings are so chosen that the voltages of thesewindings will be series-aiding and will be efiective to cause current to flow over the following path: from the upper terminal of secondary S through shoe I, rail R shoe 2, secondary S shoe 3, rail R. and shoe 4, to the lower terminal of secondary S Consequently, the voltages of both windings S and S will be effective to break .downany resistance film which may exist between the contact shoes and the rails. ,Interposed between the generator G and the trans-former primary P, is a reactor X, the. purpose of which is to limit the, maximum film break-down current which can flow, in order to economize the output of generator G, and, consequently, to limit the drain on the battery B. That is to say, the combination of transformer T and reactor X is such that with the secondary windings S and S on short circuit, the amount of current which will flow through the secondary circuit is determined by the impedance of the reactor X and the ratio of turns between the primary P and the secondaries S and S If an attempt is made to increase the open circuit secondary voltage of transformer T by decreasing the ratio of turns between the primary and the secondaries, the amount of current which will flow through the short circuited secondary windings will be decreased since it is proportional to the turn ratio. The important feature of my invention is the provision or means for increasing the open circuit secondary voltage available to break down the rail film, without changing the amount of short circuit current which will flow after the film has been broken down, and I accomplish this result by connecting a condenser C in multiple with the primary of transformer T. By means of this condenser, it is possible to increase the open circuit secondary voltage for a given ratio of transformer turns, with the result that a high voltage is available for breaking down the film without increasing the short circuit secondary current beyond the desired amount.

Referring to the vector diagram in Fig. 2, EP represents the voltage across the primary of transformer T with the secondaries on open circuit. IM is the magnetizing current of the transformer T for this voltage, and I0 is the current taken by the condenser C, making a total current of IT flowing from the generator G. The total current IT pro duces a voltage drop across reactor X, which is shown as Ex, and the total generator voltage is Ea, which, as will be seen, is very much smaller than voltage across the primary of the transformer is reduced to a very small value, with the result that the current'rtaken by the condenser C is negligible in comparison to the load current. The

current then flowing in the short circuited sec- .ondaries' is determined solely byrthe amount of primary current, and this in turn is determined by the value of reactor X, the generator voltage, and the ratio of turns between the primary P and the secondaries S and S Q a 'The apparatus shown in Fig. 1 may be modified by omitting the reactor X and replacing this re- 7 actor by a condenser so proportioned as to balance the inherent reactance of transformer T. This modification requires one less piece of apparatus, but the condenser would have to be of considerably higher capacity than with the arrangement shown in Fig. 1. v The present application is closely related to my copending application for Track shunting apparatus, Serial No. 678,629, filed July 1, 1933, which latter application contains claims which cover broadly certain features of the invention disclosed in myrpresent application. a

; Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a stretch of railway track and a rail vehicle travelling thereon, a transformer on the vehicle having a secondary connected with a rail surface for disrupting the resistance film found on such surface, a circuit for the primary 0! said transformer including a source 7 of current and a reactor, and a condenser connected in multiple with said primary for increasing the open circuit voltage of said secondary whereby the voltage available for disrupting the transformer on the vehicle having two secondaries each of which is connected across the two rails of the track, the instantaneous relative polarities of said connections with either rail being opposite-so that the voltagesof said two secondaries will aid each other in breaking down the :rail contact re sistance, a circuit for the primary of said transformerincluding a source of current and a reactor, and a condenser connected in multiple with said primary for increasing the open circuit voltage of said secondary whereby the voltage available for disrupting'the film is increased-without changing the amount of short circuit current which will flow after the film has been broken down BERNARD E. OHAGAN.

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