AU2008209302A1

AU2008209302A1 - Device for the contactless determination of the energy requirements of a point actuating drive

Info

Publication number: AU2008209302A1
Application number: AU2008209302A
Authority: AU
Inventors: Gunther Jernej; Dietmar Tafeit
Original assignee: Voestalpine VAE GmbH; Voestalpine Weichensysteme GmbH
Current assignee: Voestalpine Turnout Technology Zeltweg GmbH; Voestalpine Railway Systems GmbH
Priority date: 2007-01-23
Filing date: 2008-01-17
Publication date: 2008-07-31
Anticipated expiration: 2028-01-17
Also published as: ZA200905066B; EP2091799B1; SI2091799T1; EP2091799A2; PL2091799T3; WO2008089502A3; ATE467542T1; CH699828B1; HRP20100358T1; RS51352B; PT2091799E; BRPI0808376A2; DE502008000655D1; DE202007008329U1; DK2091799T3; ES2346021T3; AU2008209302B2; WO2008089502A2

Abstract

The invention relates to a device for the contactless determination of the energy requirements of a point actuating drive (7), comprising asynchronous motors which are connected to a three-phase current source (1) via conductors. According to the invention, at least one inductance coil is mounted in parallel to a phase conductor and the conductor that is connected to the inductance coil is guided in the opposite direction at or through a sensor (5), wherein the blind current component produced in the throttle (4) compensates at least partially the blind current component that is, in addition to the effective power component, contained in the line which is guided via the motor winding.

Description

Device for the contactless determination of the energy requirements of a point actuating drive The invention relates to a device for the contactless determination of the energy demand of a switch actuating drive, including asynchronous motors connected to a three-phase current source via conductors. In order to recognize failures in the operating behaviour of an actuating drive of a railway switch in due time, a number of devices and diagnostic modules have become known. For changing switches, a mechanical switch rod assembly moved by a switch drive is used in conventional switch actuating systems. Dirt and/or corrosion as well as other environmental impacts may lead to a sluggishness of the switch tongue, which may result in switching failures. For such switch actuating drives, asynchronous motors which are controlled by a signal box via a four-wire interface are most frequently used. Alternating voltages are carried by the four conductors, two conductors being usually supplied with phase shifted alternating voltages. Asynchronous motors are characterized by having very high portions of idle current in the idle or unloaded state. The portion of idle current decreases when a load is exerted on the switch drive, whereby the respective phase-angle-dependent factor cos # of about 0.2 will rise to about 0.5 to 0.6 when the switch drive has reached its maximum actuating force during switching. In principle, the power dissipation is taken into account by a number of known diagnostic devices. It is, in particular, common to calculate the power dissipation from a line resistance calculated from the layout chart of the arrangement, i.e. of the switch drive. A number of other solutions contemplate the 2 measurement of the line resistance by the aid of direct current, thus eliminating at least the idle resistance, and hence the idle portion of the switch drive motor output. Such solutions, however, involve additional circuit complexity for the control of the switch drive, and hence additional costs. In this context, it is known from DE 3715478 to arrange a current tracer on all three phases R, S and T of a switch transformer and the middle conductor of the three-phase drives. From DE 19749842, a diagnostic module is to be taken, which need not be connected with the central evaluation unit during checking and requires a relative small supply voltage, which can be activated via at least one of the connections provided at the structural unit, or via an external signal. Voltage signals and current signals are evaluated, whereby the circuitry is, in the main, again inter fered with. In EP 1541441, the input power of the switch drive is determined by a power measurement during the switching procedure. In that case, the line resistance and/or the power dissipation are determined, and the overall power input of the three-phase motor is measured and corrected using a power correction value depending on the power dissipation. To this end, the voltage, current and phase angle have to be determined with the motor still idle in order to find out the direct resistance of the electric circuit. Just as with the switch diagnostic device known from WO 01/85523, measuring will only be enabled if the wiring is interfered with in a contact-bound manner. In WO 01/85523, the switch diagnostic device on the input side is separated from the feed lines of the drive outside the actual circulation phase of the three-phase motor. EP 734932 too shows and describes a contact-bound device in which electric test signals are fed, via individual generators, into the lines leading to the three-phase drive to thereby enable the assessment of measured values through the signals influenced by the three-phase drive. A contactless device can be taken from EP 1535819, which, for measuring the electric current, suggests the 3 arrangement of a test coil in the region of a sensor, through which test coil a current pulse predefined in terms of current value and current direction is sent. No measurement of the idle current portion is performed by such a device, which merely serves to recognize electric current in the lines of a safety engineering device. The invention now aims to provide a device of the initially defined kind, which, for the assessment of the state of a switch, enables the enhanced detection of the actual input energy demand of a three-phase motor during the switching procedure of a switch drive and, in particular, the evaluation of larger signals freed of error sources and, in particular, idle current components. The device according to the invention is to be operable with low energy consumption in a contactless and non-reactive manner, without interfering with the safety engineering circuit. To solve this object, the device according to the invention essentially consists in that at least one choke, in particular an inductance coil, is arranged in parallel with a phase conductor, and the conductor connected to the choke is guided on or through a sensor in a manner opposite to the phase conductor connected with the motor, wherein the idle current component contained in addition to the active power component in the line guided across the motor winding is at least partially compensated by the idle current component produced in the choke. It is, thus, proceeded in a manner that a choke is arranged in parallel with a phase conductor of the asynchronous motor to generate an idle current component, and that the phase conductor and the conductor guided from the choke to the return conductor are guided in a mutually opposite manner and scanned by a sensor, thus at least partially compensating, by the idle current component produced in the choke, the idle current component contained in addition to the active power component in the line guided across the motor winding. Departing 4 from the initially assumed power supply means, i.e. switch transformers, which provide three-phase grids, and departing from the fact that such switch transformers provided on the provider side are switched into the respective switch position with the correct phase position, the invention safeguards that a predefined idle current component is produced across the choke, and due to the fact that the conductor conducting this predefined idle current component is scanned by a sensor in a sense opposite to the respective phase conductor, it is rendered feasible to subject to evaluation an accordingly compensated and idle-current-portion-adjusted signal. It is thereby basically rendered feasible to obtain a measurement result during the change of a switch via the sensor such as, e.g. an appropriate current transformer, and an evaluation electronics, in which measurement result the opposite idle current inductively produced via the choke is accordingly subtracted from the current flowing in the phase and an almost full idle current compensation can be effected so as to obtain an output signal in which the idle current portion has been nullified and an increase in the energy used for the switching procedure has thus become substantially more clearly detectable. The apparent current of the three-phase drive, which is measured in the connection line, is in fact compensated by the equiphase idle current, which can be achieved by accordingly simple means and constructive solutions. In a particularly suitable manner, the T-phase, which is emitted by the switch operating assembly always in the same phase position relative to the switch drive, is used for these purposes. In order to be able to additionally recognize the switching direction in which the switch drive is acted upon, the device according to the invention is advantageously further developed to the effect that at least one further sensor is arranged on or about a phase conductor, in particular outer conductor, and the return conductor extending opposite to this phase, wherein the phase conductor and the 5 return conductor are evaluated using said further sensor in order to determine the direction of rotation. In this case, the current flowing across the R-phase or first phase, along with the return conductor, is detected by a further current transformer, and the switch position, during a switch rotation, is again detected by the connected evaluation electronics and assigned to the measured energy used during the switch change. To this end, the fact is exploited that no noteworthy current increase is recognizable during the first 200 ms at the change into a first direction. During that same time window in which currents through the current transformer from the outer conductor and the return conductor annul each other in the output signal from the current transformer, an output signal can be obtained into the other switching position, which comprises a distinct current increase, thus enabling the switching direction to be determined by the evaluation electronics. As already pointed out in the beginning, it is, in the main, of particular advantage for the determination of the absorbed energy demand of the three-phase drive of a switch to use the T phase, which is always emitted in the same phase position relative to the switch drive by the switch actuating assembly. In principle, compensation requires the respective currents to be conducted on or through the sensors in opposite direction, to which end the device is advantageously devised such that the respective phases and the return conductor, respectively, pass through the sensors in the axial direction, wherein current transformers or current clamps are advantageously used as said sensors. The device according to the invention for the contactless determination of the energy demand of a switch actuating drive including asynchronous motors connected to a three-phase current source via conductors is devised such that at least one choke 6 coil is arranged in parallel with a phase conductor and the conductor connected to the choke coil is guided on or through a sensor in a manner opposite to the phase conductor connected with the motor, wherein the idle current component contained in addition to the active power component in the line guided across the motor winding is at least partially compensated by the idle current component produced in the choke. In this manner, the desired compensation or annulment of the idle current portion produced in the inductance coil is guaranteed, wherein suitable dimensioning may be adopted to improve compensation. Three-phase switch drives, for instance, have maximum actuating currents of about 4 A. In those cases, it will definitely suffice to use an accordingly smaller-dimensioned choke designed, e.g., for 0.6 to 0.7 A, in which case the respective signal compensation will be feasible in a simple manner in that the line in the current transformer is multiply conducted therethrough, wherein the number of windings used in this context can be selected as a function of the rated power input of the three-phase motor. The device according to the invention is, therefore, dimensioned or designed such that the conductor connected to the choke is conducted on or through the sensor in a manner opposite to the phase conductor, either singly or multiply in the form of conductor windings, whereby, with the use of the previously mentioned choke, which may be designed for 0.6 to 0.7 A, an almost full compensation of the idle current portion for a 0.5 KW three-phase motor having but one winding, and for a 1.1 KW motor including, for instance, three windings, will do to compensate for the idle current portion. The device according to the invention is advantageously further developed such that at least one further sensor is arranged on or about a phase conductor and the return conductor extending opposite to said phase, thus enabling an assignment according to its power data to the switching direction.

7 If several three-phase switch drives are operated from a single signal box, the number of chokes will not have to be increased. The configuration may rather be devised such that a common choke is provided for a plurality of asynchronous motors. The collected data of the evaluation electronics can be transmitted in a conventional manner via industrial communication interfaces to a server of the provider, whereby the server may perform the respective storage and visualization of the measured data. It is, in particular, feasible to use appropriate evaluation routines and carry out comparisons with reference curves in order to enable the early detection of problems and sluggish behaviours of switch actuating drives. The measured signals allow for a markedly improved visualization and recognition of deviations than would be feasible with the evaluation of signals without idle current compensation. In the following, the invention will be explained in more detail by way of the drawing. Therein, Fig. 1 is a schematic illustration of the measuring principle for a switch drive; Fig. 2 shows the respective circuit arrangement for several switch drives controlled by a common signal box; and Fig. 3 is a diagram indicating the values measured after idle current compensation. In Fig. 1, the current supply is schematically indicated by 1 and comprises a switch transformer providing the three rotary current phases R, S and T as well as the return conductor as a four-wire connection. The individual phases R, S and T, via fuses 2, are each conducted to a switch actuating assembly 3, said switch actuating assembly being located in a signal box. In the signal box, a choke 4 is, furthermore, applied to the T phase, wherein the device according to the invention 8 substantially comprises two sensors 5 and 6 with the associated evaluation electronics. The sensor 5 encompasses the R-phase, and hence an outer conductor, as well as the return conductor, wherein the switching direction of the switch drive can be deducted from the signal obtained here. The switch drive is schematically indicated by 7. The choke 4 generates an idle current portion, which is carried through the sensor 6 via lines 8 either singly or in several windings, and returned to the return conductor RL. The current passes the sensor 6 in the sense of arrow 9, and hence opposite to arrow 10, which indicates the current direction in the conductor of the T-phase to the switch drive 7. The idle current portions in the sensor 6, which are conducted in opposite direction, compensate the respective idle current portion in line 10 such that a compensated signal which is characterized by a small, or optimally no, idle current portion will be tapped at the sensor 6. The device comprising the measuring coils or sensors 5 and 6, like the switch actuating assembly 3 and the choke 4, are located in the signal box, with the continuing conductors of the R, S and T phases being conducted to the switch drive 7. In the illustration according to Fig. 2, the reference numerals of Fig. 1 have been retained, wherein a single choke 4 is arranged in the T-conductor for a plurality of switch drives 7. Apart from that, the illustration corresponds to that of Fig. 1, wherein separate sensors 5 and 6 are, of course, provided for each switch drive 7 to safely monitor the individual drives. Fig. 3 finally depicts the respectively compensated measuring signal, the compensated actuating current reduced by the idle current portion being plotted on the y-axis and the time coordinate being indicated on the x-axis. At the beginning, the actuating current rapidly decreases, which is not least due to the rapid decrease of the idle current portion, the compensation 9 naturally taking effect only after this starting current. After about 1.5 s, the unlocking phase is apparent from the diagram according to Fig. 3, followed by the switching phase after about 3.4 s. After about 4.4 s, the locking phase is reached, whereupon the actuating current again decreases accordingly. In the entire switching area over the unlocking phase, the switching phase and the locking phase, the actuating current ranges between a minimum value, which in the present case is indicated by 1.2 A, and a maximum value of 1.45 A, wherein the fact that the actuating current remains within this admissible range during the critical switching period, is to be taken as an indicator for the proper functioning of the switch actuating drive.

Claims

1. A device for the contactless determination of the energy demand of a switch actuating drive (7), including asynchronous motors connected to a three-phase current source via conductors, characterized in that at least one choke (4), in particular an inductance coil, is arranged in parallel with a phase conductor, and the conductor connected to the choke (4) is guided on or through a sensor (5) in a manner opposite to the phase conductor connected with the motor, wherein the idle current component contained in addition to the active power component in the line guided across the motor winding is at least partially compensated by the idle current component produced in the choke (4).

2. A device according to claim 1, characterized in that the T phase is selected as the phase conducted across the choke (4).

3. A device according to claim 1 or 2, characterized in that at least one further sensor (6) is arranged on or about a phase conductor, in particular outer conductor phase, and the return conductor extending opposite to said phase, wherein the phase conductor and the return conductor are evaluated using said further sensor (6) in order to determine the direction of rotation.

4. A device according to claim 1, 2 or 3, characterized in that the respective phases and the return conductor, respectively, pass through the sensors (5, 6) in the axial direction.

5. A device according to any one of claims 1 to 4, characterized in that current transformers or current clamps are used as said sensors (5, 6). 11

6. A device according to any one of claims 1 to 5, characterized in that a common choke (4) is provided for a plurality of asynchronous motors.

7. A device according to any one of claims 1 to 6, characterized in that the conductor connected to the choke (4) is conducted on or through the sensor (5) in a manner opposite to the phase conductor, either singly or multiply in the form of conductor windings.