US935069A - Selective a.c.-d.c. system. - Google Patents

Description

J. P. TEITLE.

SELECTIVE A. G.- D. G. SYSTEM.

APPLICATION FILED JAN. 18, 1908.

935,069 Y Patented Sepfi.28,1909.

AL. 11c.

Witnesses Invendor John F. Trifle UNITED STATES EATENT OEETQE.

JOHN F. TRITLE, OF SCHENEC'IADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

SELECTIVE .A.G.-D.C. SYSTEM.

T 0 all whom it may concern:

Be it known that 1, JOHN E. TnrrLu, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Selective AC.- DC. Systems, of which the following is a specification.

In electrically driven cars intended for operation either on alternating or direct current, usually high potential alternating current and low potential direct current, the change from one to the other being ordinarily made while the car is moving, it is customary to provide a system of selective switches arranged to automatically connect the current collecting device to the proper circuits of the car for either alternating or direct current operation. Such a system of selective switches is shown in the patent to Frank and Pevear, No. 854730, dated May 28, 1907, Control of electric cars. The arrangement there shown consists of a small stepdown transformer, having its primary connected to the power circuit, the actuating coil of the AC. switch being connected across the secondary of said transformer, and the actuating coil of the DC. switch being in series with the primary of said transformer. WVith this arrangement the AC. switch is operated only when the current collecting device is receiving alternating current, and the DC. switch is supposed to 0perate only when the current collecting device connects with a source of direct current.

Itis found in actual practice that a system such as that mentioned above is open to the objection that when the car enters an alternating current section the first rush of current, before the counter E. M. E. of the transformer has had time to build up, may operate the DC. switch. Such an occurrence is, of course, highly objectionable, and it is an object of my invention to provide means for absolutely and certainly preventing the 11C. switch from operating when the car enters, or while it is on, an alternating current section.

To the above end my invention consists in providing a slow acting relay, the actuating coil of which is in series with the primary of the transformer and the actuating coil of the DC. switch. Said relay has contacts which, when the relay is in its deenergized position, complete a circuit through a Specification of Letters Patent.

Application filed. January 18, 1908.

Patented Sept. 28, 1909.

Serial No. 411,452.

non-inductive resistance in shunt to the actuating coils of the relay and the DC. switch. Said relay also carries contacts which, when the relay is in its deenergized position, complete a circuit in shunt to the whole or a part of the actuating coil of the DC. switch.

My invention will be more clearly understood from the following description taken in connection with the accompanying drawing, in which I have shown diagrammatically one form in which it may be embodied. I deem it unnecessary to illustrate in connection with my invention any system of motor control, as it is obvious that my invention is altogether independent of any particular control system. I may, however, state that, as illustrated, my selective All-DO. system is applicable to the system of control set forth in a patent issued in the name of George H. Hill, No. 904,780, dated Novembel 24, 1908.

Referring tothe drawing, L represents the trolley wire or other supply conductor with which the trolley T or other current collecting device carried by the car engages. It is to be assumed that the supply conductor is at some places supplied with alternating, and at other places with direct current, the potential of the alternating current section being usually high, for example, 6600 volts, and the potential of the direct current section being relatively low, for example, 600 volts.

The usual kicking coil and lightning arrester are indicated in a well-known conventional manner at A.

The main switch which is intended to close only on alternating current operation is indicated at S, and the main switch which closes only on direct current operation is shown at S These switches S and S may be of any suitable design.

A small step-down transformer represented at E has its primary connected between trolley and ground. coil 1 of the AC. switch S is connected across the secondary of the transformer E, and the actuating coil 2 of the DC). switch S is connected in series with the primary of the transformer E.

A relay M is arranged with its actuating coil 3 in series with the actuating coil 2 of the switch S This relay is retarded in its upward movement by a dash pot a which, however, does not interfere with its falling The actuating l (if) and quickly when the actuating coil is deenergized. The relay M controls two sets of contacts, one of which, 5, completes a circuit to ground through the non-inductive resistance (3 in shunt to the actuating coils '3 and 2 of the relay hi and the switch 53, while the other T connects some point 8 on the coil 2 to ground, thereby shunting more or less of the coil 2 of the switch S A contact 9, controlled by the All switch' to, is arranged to cut an inductive resistance 10 into circuit with the coil 1 so as to reduce the current flow in this coil after the switch to has closed. Similarly, a contact 11, controlled by the switch S cuts into circuit with the coil 2 a resistance 12 which serves to reduce the current in the coil 2 after the switch S has closed.

The operation of my selective system is as follows: Suppose the switches {*5 and band the relay M to be in the positions illustrated, which are those which they assume when no current is passing to the collecting device. If the collecting device is now caused to engage with a section of trolley wire or third rail carrying alternating current at high potential, current will flow through the pri- 1n ary of the transformer E, through the noninductive resistance (3, contact 5 of the relay M to ground. The resistance 6 being noniinductive will offer but little lundrance to the flow of the alternating current and most of it will pass to ground by this path. The first sudden rush of current before the counter E. M. F. of the transformer E has had time to build up may be excessive and some current may flow through the actuat ing coil of the relay M and the actuating coil 2 of the switch S The portion of the actuating coil 2 below the point 8 will, however, receive practically no current, since it is shunted by the wire which connects the point 8 to ground through the contact 7 on the relay M, and the point 8 on the coil 2 is so chosen that the current flowing through the upper part of the coil 2 at this time is insutlicient to operate the switch S If the point 8 is suitably located intermediate the ends of the coil 2, the magnetic field produced by the upper part of the coil 2 may be wiped out by the opposing field pro duced by the lower part of the COll which is short-circuited through ground and which, therefore, acts as the secondary of a t-rans former of which the upper part of the coil 2 is the primary. The relay M will not op crate on this sudden rush of current owing to the retarding effect of the dash pot 4;. As the counter E. M. F. of the transformer E soon builds up, the current passing through its primary quickly dies down and practically all of it passes to ground through the non-inductive resistance (3, owing to the reactance of the coils 3 and 2. At the same time the current induced in the secondary of the transformer E passes through the actuating coil 1 of the switch b and causes this switch to close. The closing of the switch bl opens the contact 9 and breaks the short circuit around the inductive rcsistanc-c ,4 thereby causing a cutting down of the current flowing in the. actuating coil .l, the current needed to hold the switch b closed being much less than that required to close it.

If, on the other hand, the collecting device T is connected to a source of direct current, current will pass through the primary of the transfia'mer .ll. through the coil 3 and the upper part of the coil to the point 8 and to ground, through the contact 7. The resistance (3 will etl'ectively prevent any great amount of current from passing to ground through the contact 5. Under this condition the energization of the coil 2 of the switch to will be insul'licient to operate this switch, but the current passing through the coil 3 will be enough to cause the relay M to pull up, an operation which will, however, be impeded by the dash pot l. is soon as the contact 7 opens, the shuntcircuit from the point 8 is interrupte .l, and the current passing through the coil :3 must pass through the whole of the coil 2 to ground. The excitation of the coil 2 is now sullicient to cause the switch S to operate and it closes. After the main contacts on the switch 5 have closed, the short circuit around the resistance 12 is interrupted at the contact 11, and the current passing through the primary of the transformer E, the coil 3 and the coil 2 is cut down and heating of these coils thereby avoided. When the contact 5 opens, the circuit to ground through the non-inductive resistance (3 is interrupted and all of the current must flow through the coils 3 and While I have shown but one form in which my selective A.C.D.C. system may be embodied, I wish it understood that I do not mean to conline myself to this particular arrangen'ient, but that l ailn to cover all such modifications as will occur to those skilled in this art and are within the scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is,

l. A selective All-11C. system for electric cars comprising a transformer having its primary connected to the power circuit, an 31.0. switch, an actuating coil therefor connected to the secondary of said transforn'ier, a DC. switch, an actuating coil therefor connected to the power circuit through the primary of said transformer, a slow acting relay having its actuating coil arranged in series with the prin'iary of said transformer and the actuating coil of said lit}. switch, a shunt circuit containing a non-inductive resistance around the actuating coil of said relay and the actuating coil of the DC. switch, and contacts controlled by said relay when it is in its deenergized position for shunting more or less of the actuating coil of the DC. switch.

2. A selective A.C.-D.O. system for electric cars comprising a transformer having its primary connected to the power circuit, an AC. switch, an actuating coil therefor connected to the secondary of said transformer, a D.C. switch, an actuating coil therefor in series with the primary of said transformer, a slow acting relay having its actuating coil in series with the primary of said transformer and the actuating coil of said DC. switch, a non-inductive resistance, contacts controlled by said relay and closed when said relay is in its denergized position for shunting the actuating coils of the relay and the D.O. switch through said non-inductive resistance, and other contacts controlled by said relay also closed when said relay is in its deenergized position for shunting more or less of the actuating coil of the DO. switch.

3. A selective A.C.-D.C. system for electric cars comprising a transformer having its primary connected to the power circuit, I

an A.C. switch, an actuating coil therefor connected to the secondary of said transformer, a DC. switch, an actuating coil therefor in series with the primary of said transformer, a relay having its actuating coil in series with the primary of said transformer and the actuating coil of said DC. switch, a non-inductive resistance, contacts controlled by said relay closed when the relay is in its denergized position for shunting the actuating coils of the relay and the DC. switch through said non-inductive resistance, other contacts controlled by said relay also closed when. said relay is in its deenergized position for shunting more or less of the actuating coil of the 11C. switch, and means for rendering the relay slow acting in its opening of the contacts controlled by it without interfering with the quick closing of said cont-acts when the actuating coil of the relay is deenergized.

In witness whereof, I have hereunto set I my hand this 16th day of January, 1908.

JOHN F. TRITLE. Witnesses:

BENJAMIN B. HULL, IIELEN ORFORD.

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