US3571667A - Track circuit of great length - Google Patents

Track circuit of great length Download PDF

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Publication number
US3571667A
US3571667A US807237A US3571667DA US3571667A US 3571667 A US3571667 A US 3571667A US 807237 A US807237 A US 807237A US 3571667D A US3571667D A US 3571667DA US 3571667 A US3571667 A US 3571667A
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winding
output
magnetic circuit
circuit
voltage
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Expired - Lifetime
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US807237A
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English (en)
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Jean Demeur
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Umicore NV SA
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Acec
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B61—RAILWAYS
    • B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
    • B61L1/00—Devices along the route controlled by interaction with the vehicle or train
    • B61L1/18—Railway track circuits
    • B61L1/181—Details
    • B61L1/188—Use of coded current

Definitions

  • the receiver in- 1 o earch 317/147 eludes an amplitude discriminator for eliminating the signals [561 :12212122158 3322;1zsitaizrgrsvtszfirs'xzsttr; 2 975 272 3/ T Z I PATENTS 7/ when its input is energized by a signal at the above-mentioned emc eta 31 147X repetition rate.
  • This invention relates to a track circuit for detecting the presence of a train on a long section of a railway track equipped with an AC traction power line, wherein the two rails of of the section are insulated from the adjoining sections at each end thereof.
  • Track circuits are known comprising in a conventional manner a generator for producing a voltage between the two rails at one extremity of a railway section and a receiver at the other extremity of the railway section for energizing a railway relay which is operated when the axle of a vehicle short circuits the two rails.
  • a certain number of conflicting conditions appear the most important of which concerns the frequency of the currents used in the track circuit. indeed, if the chosen frequency is high, the output voltage of the generator used must be high because of the high impedance of the railway line, which requires a generator having a high output railway rating.
  • the railway windings for the transmission of the traction current as well as the self inductances and the condensators used in the operation of generator and of the receiver take prohibitive dimensions.
  • the frequency must also be such that it may not be confused with the stay frequencies and more particularly with the frequency of operation of the traction power line or of its harmonics.
  • the track circuit in accordance with the invention overcomes all the above-mentioned difficulties. It comprises a generator adapted to generate a voltage whose frequency is approximately equidistant from the fundamental frequency of the power line and from the second harmonic thereof, the generated voltage being in the fonn of trains of pulses at a very low repetition rate.
  • the invention also comprises a receiver including an amplitude discriminator adapted to eliminate the signals the amplitude of which is lower than a predetermined level and a selective demodulator which provides an output only when its input signal is at said repetition rate.
  • the amplitude discriminator comprises two magnetic circuits having rectangular hysteresis characteristics.
  • the first one of said magnetic circuits has a single winding and the second one of said magnetic circuits has a first and a second winding operating as a transformer, the single winding of said first magnetic circuit having more turns than the first winding of the second magnetic circuit.
  • the single winding of the first magnetic circuit is connected in series with the first winding of the second magnetic circuit and both windings receive the input voltage while the output voltage is provided by the second winding of the second magnetic circuit.
  • the demodulator comprises an input transformer having a primary winding to which is applied the input of the circuit and two secondary windings the first one of which feeds a first winding of a magnetic circuit having a rectangular characteristic.
  • a second winding of the last-mentioned magnetic circuit feeds an output transformer through a first winding of a second magnetic circuit having a rectangular characteristic.
  • a second winding of the last-mentioned second magnetic circuit is fed in series with a third winding of the last-mentioned fist magnetic circuit by the output current of a transistor the base of which is fed through a potentiometer by the output voltage of the second secondary winding of the input transformer.
  • Means are also provided to equalize the current of the transistor in the two windings that such transistor feeds.
  • FIG. 1 illustrates schematically a circuit for generating a voltage applied between two rails of a railway section
  • FllG. 2 illustrates schematically a circuit for receiving the voltage generated by the generator
  • FllG. 3 illustrates an embodiment of an amplitude discriminator
  • Fit ⁇ . 4 illustrates an embodiment of a demodulator for use with the invention.
  • FllG It iliustrates schematically an arrangement of a generator adapted to feed a voltage which is applied between the two rails of a long railway section electrically insulated from the adjoining sections, such long railway section forming part of a railway track equipped with an AC traction power line. It comprises a pilot oscillator connected to a separator stage S having a high input impedance so as not to interfere with the stability of the oscillator O. The separator synchronizes a relaxation oscillator 0R which in turn feeds a power amplifier A the output voltage V of which feeds the two rails at one extremity of a railway section not shown.
  • the output current of the amplifier A acts on the amplitude of the output current of relaxation oscillator 0R through a regulator Rg the input of which is connected to a modulator M which causes the generation of trains of pulses by the relaxation oscillator OR for a certain duration and at a predetermined repetition rate, these two parameters being separately regulated and the regulator Rg being used to maintain the input current of amplifier A within limits compatible with the good operation and the absence of overload on the transistors forming part of such amplifier.
  • the frequency of the traction power line being 50 Hz
  • the frequency of the oscillator 0 and consequently the frequency of output voltage V is 73 Hz., which is the mean value between the fundamental frequency and the second harmonic of the traction power line.
  • Fig. 2 illustrates schematically the receiver which is located at the extremity of the railway section which is opposed to the generator, Such receiver is fed by the input voltage E appearing between the two rails and filtered by a filter F which blocks the undesired frequencies located on each side of the useful frequency of 73 Hz. and more particularly the frequencies of 50 and Hz.
  • the output of filter F is connected to an amplitude discriminator DA which will be described more fully in a later part of the disclosure.
  • Such discriminator eliminates the signals the amplitude of which is lower than a predetermined level and is followed by an electronic multivibrator B providing rectangular signals which, after amplification by an amplifier A,, are demodulated by a circuit D which will equally be disclosed more fully in a later part of the application.
  • the demodulated signals, after amplification by an amplifier A are applied to a railway relay R through a rectifier RD.
  • the amplitude discriminator DA of FIG. 2 is illustrated in FIG. 3. It comprises two saturable reactors T01 and T02 having windings the number of turns of which is n, and n respectively.
  • the saturable reactor T01 has a single winding only but the saturable reactor T02 also has a second winding providing an output voltage U
  • the single winding of saturable reactor T01 and the first winding of saturable reactor T02 are connected in series.
  • the number of turns n of saturable reactor T01 is higher than the number of turns n of saturable reactor T02 and, as these two saturable reactors have rectangular magnetic characteristics, as soon as the current in the two windings in series reaches a predetermined valve, such current saturates reactor TOll but not T02.
  • the result of this is that the impedance of the single winding of T01 is rendered practically nul and that the voltage U, applied to these two windings in series is applied mainly to the first winding of reactor T02 which consequently provides a maximum output voltage U, across the second winding thereof.
  • the amplitude discriminator eliminates the action of the voltages which are too low and among which are located the different voltages originating from the traction power line which voltages are, as explained previously, substantially blocked by the filter F.
  • E10. 4 illustrates schematically an embodiment of the demodulator D of H0. 2. It comprises two saturable reactors T03 and T04 made of a material having a rectangular magnetic characteristic.
  • the first saturable reactor T03 has three windings n in, and the second saturable reactor T04 has two windings n, and a
  • the demodulator receives its input voltage from a transformer TlRi having two secondary windings the first one of which feeds the winding n through a resistor r and the second one of which is connected to a potentiometer P the function of which will be explained later.
  • Winding n of reactor T03 feeds the primary of output transformer TR2 through the winding n, of saturable reactor T04.
  • a transistor T connected to a biasing source AL has its base emitter circuit fed by the potentiometer P and its collector current flows through the windings n, and n in series with a filtering self inductance L.
  • a condensator C having a high capacity is used to equalize the variation of the collector current of transistor T because its base is fed by an alternating current. It is obvious that when an alternating voltage which is not modulated is applied to the primary of transformer TRll, for a predetermined regulation of potentiometer P, there is obtained a maximum emitter current in transistor T and this current is lowered more and more as the generated voltage is modulated by pulse trains of shorter duration and consequently with longer time intervals between such trains of pulses because, as it has been mentioned previously, the repetition rate is constant.
  • reactors T03 and T04 are not saturated; reactor T03 operates as a transformer but, because reactor T04 is not saturated, the winding n which has been specially designed for that purpose has a very high reactance so that the output voltage provided by transformer TR2 is low.
  • the collector current of transistor T is increased, there is a time where reactor T03 is still not saturated but where reactor T04 is saturated.
  • the reactance of winding n is lowered to almost zero and the output voltage of transformer TR2 is high.
  • reactor To3 is also saturated and the coupling between windings n, and n is lowered and consequently the output voltage of transformer TR2 is also lowered.
  • the elements of the circuit and the regulation of potentiometer P are established in such a way that the demodulator provides an output voltage at the predetermined frequency of modulation of the generator. For the other frequencies of modulation of the pulse trains and for a continuous voltage generation, the output is negligible. it is important to not that the circuit illustrated in MG. 4 is fool proof because any accidental defectiveness of one of the elements thereof results in the absence of an output voltage.
  • the amplitude discriminator comprises two magnetic circuits having rectangular magnetic characteristics, the first one of said magnetic circuits having a single winding, the second one of said magnetic circuits having a first and a second windings, the single winding of said first magnetic circuit having more turns than the first winding of the second magnetic circuit, the single winding of said first magnetic circuit and the first winding of said second magnetic circuit being connected in series and receiving the input voltage while the output voltage is provided by the second winding of the second magnetic circuit.
  • said demodulator comprises a transformer having a primary winding for receiving an input voltage and two secondary windings a irst magnetic circul having a rectangular charac enstic an having a first winding connected to the first one of said secondary windings, said first magnetic circuit having a second winding connected to an output transformer; a second magnetic circuit having a rectangular characteristic and having a first winding connected in the input of said output transformer, said second magnetic circuit having a second winding connected in series with a third winding of said first magnetic circuit; a transistor connected to the second winding of said second magnetic circuit and the third winding of said first magnetic circuit; and a potentiometer having a first and a second terminals connected to the second one of said secondary windings, and an intennediate terminal connected to the base of the transistor.
  • a track circuit as defined in claim 1, wherein said generator comprises a pilot oscillator; and separator stage connected to said pilot oscillator; a relaxation oscillator connected to said separator; a power amplifier connected to the output of said relaxation oscillator for providing the output voltage applied to the railway section; a regulator connected to the output of said amplifier, said regulator being responsive to a modulator for causing said relaxation oscillator to generate trains of pulses lasting a predetermined time duration with a predetermined time interval between each train of pulses.
  • said receiver comprises a filter adapted to block the fundamental and the second harmonic of the traction power line, the amplitude discriminator being connected to the output of said filter; an electronic multivibrator connected to the output of said amplitude discriminator; an amplifier connected to the output of said electronic multivibrator, the demodulator being connected to the output of said amplifier; a second amplifier connected to the output of said demodulator; a rectifier connected to the output of said second amplifier; and a railway relay connected to the output of said rectifier.

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  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Mechanical Engineering (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Inverter Devices (AREA)
  • Train Traffic Observation, Control, And Security (AREA)
  • Arrangements For Transmission Of Measured Signals (AREA)
US807237A 1968-03-14 1969-03-14 Track circuit of great length Expired - Lifetime US3571667A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
BE712165 1968-03-14

Publications (1)

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US3571667A true US3571667A (en) 1971-03-23

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US807237A Expired - Lifetime US3571667A (en) 1968-03-14 1969-03-14 Track circuit of great length

Country Status (9)

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US (1) US3571667A (de)
BE (1) BE712165A (de)
CA (1) CA938710A (de)
DE (1) DE1912414C3 (de)
ES (1) ES364264A1 (de)
FR (1) FR2003882A1 (de)
LU (1) LU58184A1 (de)
NL (1) NL6903960A (de)
YU (1) YU32149B (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6268995B1 (en) * 2000-06-08 2001-07-31 Jennings Technology Double-bellows vacuum variable capacitor
US20110284697A1 (en) * 2008-11-21 2011-11-24 Renato Altamura Method and apparatus for supplying a track circuit

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE757277A (fr) * 1970-10-09 1971-04-09 Acec Recepteur pour circuit de voie
AT311413B (de) * 1971-01-05 1973-11-12 Itt Austria Gleisüberwachungseinrichtung für Bahnanlagen

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2975272A (en) * 1957-04-02 1961-03-14 Itt Track circuit
US3075127A (en) * 1960-09-26 1963-01-22 Lear Siegler Inc Alternating current frequency sensing and indicating circuit
US3246142A (en) * 1961-07-14 1966-04-12 Westinghouse Brake & Signal Railway track relay circuits
US3252141A (en) * 1961-07-31 1966-05-17 Omnitronic Corp Fail-safe control system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2975272A (en) * 1957-04-02 1961-03-14 Itt Track circuit
US3075127A (en) * 1960-09-26 1963-01-22 Lear Siegler Inc Alternating current frequency sensing and indicating circuit
US3246142A (en) * 1961-07-14 1966-04-12 Westinghouse Brake & Signal Railway track relay circuits
US3252141A (en) * 1961-07-31 1966-05-17 Omnitronic Corp Fail-safe control system

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6268995B1 (en) * 2000-06-08 2001-07-31 Jennings Technology Double-bellows vacuum variable capacitor
US20110284697A1 (en) * 2008-11-21 2011-11-24 Renato Altamura Method and apparatus for supplying a track circuit
CN102264571A (zh) * 2008-11-21 2011-11-30 希尔帝股份公司 给轨道电路供电的方法和设备
US8333349B2 (en) * 2008-11-21 2012-12-18 Sirti S.P.A. Method and apparatus for supplying a track circuit
CN102264571B (zh) * 2008-11-21 2014-07-16 希尔帝股份公司 给轨道电路供电的方法和设备

Also Published As

Publication number Publication date
YU42469A (en) 1973-10-31
LU58184A1 (fr) 1969-07-10
DE1912414A1 (de) 1969-12-11
NL6903960A (nl) 1969-09-16
FR2003882A1 (fr) 1969-11-14
ES364264A1 (es) 1970-12-16
BE712165A (fr) 1968-09-16
DE1912414C3 (de) 1974-07-11
DE1912414B2 (de) 1973-12-06
CA938710A (en) 1973-12-18
YU32149B (en) 1974-04-30

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