Short circuit detection device, electronic device and short circuit detection method

Abstract

A short-circuit detection device (31) comprises a first current sensing device (32) for detecting a first current value, which is a value of a current flowing into a primary winding (21), and a second current sensing device (33) for detecting a second current value, which is a value of a current flowing out of a secondary winding (22). The short-circuit detection device (31) further comprises a short-circuit determination device (34) for determining whether a short circuit occurs in the secondary winding (22) based on the first current value and a second current value relating to the primary side, or on a first current value relating to the secondary side and the second current value calculated from the first current value, the second current value, the number of turns of the primary winding (21), and the number of turns of the secondary winding (22).

Description

Technical field

[0001] The present disclosure relates to a short circuit determining device, an electronic device and a method for determining a short circuit. Technological background

[0002] Electric railway vehicles of an AC-powered system include a transformer that transforms the voltage of AC power supplied from a substation via an overhead line into a desired voltage value, and a power conversion device that converts the AC power after voltage transformation by the transformer into a desired AC power and supplies the converted AC power to a load device. Examples of such a transformer and power conversion device to be installed in an electric railway vehicle are disclosed in Patent Literature 1. Citation listPatent literature

[0003] Patent Literature 1: Unexamined Japanese Patent Application Publication No. H6-141404 Summary of the inventionTechnical problem

[0004] Patent Literature 1 discloses an electric vehicle control device including a transformer, a power converter device, and a protection circuit for protecting a circuit. The protection circuit includes ground fault detection means connected to the ground terminal of the transformer and the connection point between the converter and the inverter of the power converter device. This ground fault detection means can detect a ground fault occurring at a position different from the predetermined ground point in the circuit of the electric vehicle control device, but cannot detect abnormalities other than the ground fault, such as a short circuit in the secondary winding of the transformer.

[0005] An object of the present disclosure achieved in view of the above situation is to provide a short circuit determination device, an electronic device and a method for determining a short circuit that can achieve a determination as to whether a short circuit occurs in a secondary winding of a transformer. Solution to the problem

[0006] To achieve the above object, a short-circuit determining device according to the present disclosure includes a first current detecting means, a second current detecting means, and a short-circuit determining means. The first current detecting means detects a first current value, which is a value of a current flowing into a primary winding of a transformer. The transformer transforms a voltage of AC power supplied to the primary winding and outputs the AC power after voltage transformation from one or more secondary windings of the transformer. The second current detecting means detects a second current value, which is a value of a current flowing from each of the one or more secondary windings.The short-circuit determination device determines whether a short circuit occurs in each of the one or more secondary windings based on the first current value and a second current value related to a primary side, or on a first current value related to a secondary side and the second current value. The second current value related to the primary side and the first current value related to the secondary side are calculated from the first current value, the second current value, the number of turns of the primary winding, and the number of turns of each of the one or more secondary windings. Advantageous effects of the invention

[0007] The present disclosure can achieve a determination of whether a short circuit occurs in the secondary winding based on the first current value and the second current value related to the primary side, or on the first current value related to the secondary side and the second current value calculated from the first current value, the second current value, the number of turns of the primary winding, and the number of turns of the secondary winding. Short description of the drawings Fig. 1 is a block diagram illustrating a short-circuit determination device and a power conversion device according to Embodiment 1; Fig. 2 illustrates an exemplary flow of a current in the case of a short circuit in a secondary winding of a transformer in Embodiment 1; Fig. 3 illustrates hardware components of the short circuit determination device according to Embodiment 1; Fig. 4 is a flowchart illustrating a short-circuit determination process performed by the short-circuit determination device according to Embodiment 1; Fig. 5 is a block diagram illustrating a short-circuit determination device and a power conversion device according to Embodiment 2; Fig. 6 is a flowchart illustrating a short-circuit determination process performed by the short-circuit determination device according to Embodiment 2; and Fig. 7 illustrates a modification of the hardware components of the short circuit determination device according to the embodiments. Description of the embodiments

[0008] A short circuit determination device, an electronic device, and a method for determining a short circuit according to some embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In the drawings, components that are identical or corresponding to each other are denoted by the same reference symbols. Embodiment 1

[0009] A typical example of an electronic device installed in a railway vehicle is a power converter device installed in a railway vehicle to convert electric power supplied from a power source into AC power to be supplied to a load device and to supply the converted AC power to a motor. A power converter device 1 installed in Fig. 1 is installed in a rail vehicle of an AC-powered system. The rail vehicle of an AC-powered system, like the power conversion device 1, is provided with a transformer 20 that transforms the voltage of AC power supplied from a power source 91 and supplies the AC power to the power conversion device 1 after voltage transformation.

[0010] The power conversion device 1 converts the AC power supplied from the power source 91 via a circuit breaker 92 and transformed by the transformer 20 into AC power to be supplied to a load device, more specifically, to a motor 93, and supplies the converted AC power to the motor 93. A typical example of the motor 93 is a three-phase induction motor for generating motive power for the railway vehicle. The power conversion device 1 includes a short-circuit determination device 31 that determines whether a short circuit occurs in the transformer 20. In response to a short circuit in the transformer 20, the power conversion device 1 opens the circuit breaker 92, thus electrically disconnecting the transformer 20 from the power source 91.

[0011] Power source 91 is installed in the rail vehicle. A typical example of power source 91 is a pantograph that receives AC power from the substation via a power supply line. The pantograph is, for example, a pantograph or a contact shoe. The power supply line is, for example, an overhead line or a third rail.

[0012] The electrical path between the power source 91 and the transformer 20 is provided with a circuit breaker 92, which electrically connects or disconnects the transformer 20 from the power source 91. The circuit breaker 92 is closed or opened by the power conversion device 1 or a circuit breaker control device (not shown). When closed, the circuit breaker 92 electrically connects the transformer 20 to the power source 91. When opened, the circuit breaker 92 electrically disconnects the transformer 20 from the power source 91.

[0013] The transformer 20 includes a primary winding 21 electrically connected to the power source 91 via the circuit breaker 92, and a secondary winding 22 electrically connected to the electronic device, more specifically, to the power conversion device 1. The transformer 20 transforms the voltage of an AC power supplied from the power source 91 to the primary winding 21 via the circuit breaker 92, and outputs the AC power after voltage transformation from the secondary winding 22 to the power conversion device 1.

[0014] One end of the primary winding 21 is electrically connected to the circuit breaker 92. The other end of the primary winding 21 is grounded via a component such as a grounding ring, a grounding brush, or a wheel, which is not illustrated.

[0015] One end of the secondary winding 22 is electrically connected to one of the primary terminals of a power converter circuit 11 included in the power converter device 1. The other end of the secondary winding 22 is electrically connected to the other of the primary terminals of the power converter circuit 11.

[0016] The power conversion device 1 is electrically connected to the secondary winding 22. The power conversion device 1 converts the AC power output from the secondary winding 22 into electric power to be supplied to the load device, more specifically, the motor 93, and supplies the converted electric power to the motor 93.

[0017] The power conversion device 1 includes the power conversion circuit 11 whose primary terminals are electrically connected to the secondary winding 22 and whose secondary terminals are electrically connected to the motor 93, a circuit control device 12 that controls the power conversion circuit 11, the short-circuit determination device 31 that determines whether a short circuit occurs in the secondary winding 22, and a circuit protection device 13 that electrically disconnects the primary winding 21 from the power source 91 when it is determined that a short circuit occurs in the secondary winding 22.

[0018] The power converter circuit 11 converts the AC power supplied from the secondary winding 22 through the primary terminals into three-phase AC power to be supplied to the motor 93, and then supplies the three-phase AC power from the secondary terminals to the motor 93. For example, the power converter circuit 11 includes a converter that converts the AC power supplied from the secondary winding 22 into DC power and outputs the DC power, a capacitor that is charged with the DC power output from the converter, and an inverter that converts the DC power supplied from the converter through the capacitor into three-phase AC power.

[0019] Both the converter and the inverter comprise several switching elements, such as insulated-gate bipolar transistors (IGBTs), gate-switching thyristors (GTOs), or metal-oxide-semiconductor field-effect transistors (MOSFETs). The switching elements perform switching operations, thus enabling the converter and the inverter to perform power conversion.

[0020] The circuit control device 12 controls the switching elements included in the power converter circuit 11 according to an operation command for the railway vehicle obtained from a driver's cab, not illustrated, and a result of a determination by the short-circuit determination device 31. For example, the circuit control device 12 transmits pulse width modulation (PWM) signals to the individual gate terminals of the IGBTs of the converter and the inverter, thus controlling the IGBTs.

[0021] While the railway vehicle is running, the circuit controller 12 controls the power converter circuit 11 according to an operation command. The circuit controller 12 stops the power converter circuit 11 when a determination result indicating the occurrence of a short circuit in the transformer 20 is received from the short circuit determination device 31.

[0022] The circuit protection device 13 controls the circuit breaker 92 according to a determination result by the short-circuit determination device 31. In detail, the circuit protection device 13 keeps the circuit breaker 92 closed while the short-circuit determination device 31 continues to determine that no short circuit occurs in the secondary winding 22. When the short-circuit determination device 31 determines that a short circuit occurs in the secondary winding 22, the circuit protection device 13 opens the circuit breaker 92 and electrically disconnects the primary winding 21 of the transformer 20 from the power source 91.

[0023] The short-circuit determination device 31 includes a first current detector 32 that detects a first current value, which is a value of a current flowing into the primary winding 21, and a second current detector 33 that detects a second current value, which is a value of a current flowing out of the secondary winding 22. The short-circuit determination device 31 further includes a short-circuit determination device 34 that determines whether a short circuit occurs in the secondary winding 22 based on the first current value, the second current value, the number of turns of the primary winding 21, and the number of turns of the secondary winding 22.

[0024] The first current detecting device 32 measures a first current value, which is a value of a current flowing in the electrical path between the power source 91 and the primary winding 21. In detail, the first current detecting device 32 measures a first current value with a current sensor CT1 of a current transformer (CT) type provided for the conductor connecting the circuit breaker 92 to one end of the primary winding 21.

[0025] The second current detection device 33 measures a second current value, which is a value of a current flowing in the electrical path between the secondary winding 22 and the electronic device, more specifically, the power conversion device 1. In detail, the second current detection device 33 measures a second current value using a CT-type current sensor CT2 provided for the conductor connecting one end of the secondary winding 22 to one of the primary terminals of the power conversion circuit 11.

[0026] The short-circuit determination device 34 determines whether a short circuit occurs in the secondary winding 22 based on the first current value and a second current value related to the primary side, or on a first current value related to the secondary side and the second current value calculated from the first current value, the second current value, and a turns ratio of the transformer 20. It is assumed that the short-circuit determination device 34 preliminarily stores information about the turns ratio of the transformer 20.

[0027] As an exemplary anomaly in the secondary winding 22, the conductor connecting one end of the secondary winding 22 to the power converter circuit 11 could be electrically directly connected to the conductor connecting the other end of the secondary winding 22 to, for example, the power converter circuit 11. This direct connection allows a current to flow through a closed circuit defined, for example, by the secondary winding 22, as indicated by the solid arrow in Fig. 2. In the case of a short circuit at a position closer to the secondary winding 22 than the current sensor CT2, no current flows in the current sensor CT2, so that the second current value to be detected by the second current detecting means 33 is sufficiently smaller than that in the case of no short circuit in the secondary winding 22.

[0028] Due to such a small second current value in the case of a short circuit in the secondary winding 22 described above, the short-circuit determining means 34 in Embodiment 1 determines whether a short circuit occurs in the secondary winding 22 based on the difference between the first current value and the second current value related to the primary side, that is, the current value on the primary side of the transformer 20 calculated from the second current value. If the absolute value of the difference between the first current value and the current value on the primary side of the transformer 20 calculated from the second current value is at least a first threshold, it is considered that a short circuit occurs in the secondary winding 22.In contrast, if the absolute value of the difference between the first current value and the current value on the primary side of the transformer 20 calculated from the second current value is smaller than the first threshold, it is assumed that no short circuit occurs in the secondary winding 22. The first threshold is defined according to a possible range of an amplitude of a current flowing into the primary winding 21. For example, the first threshold is a value calculated by multiplying the lower limit of the possible range of an amplitude of a current flowing into the primary winding 21 by a positive coefficient less than 1, for example, 0.5. It is assumed that the short-circuit determination means 34 preliminarily stores information about the first threshold.

[0029] Fig. 3 illustrates hardware components of the short-circuit determination device 31 having the above-described configuration. The short-circuit determination device 31 includes a processor 81, a memory 82, and an interface 83. The processor 81, the memory 82, and the interface 83 are connected to each other via buses 80. The functions of the short-circuit determination device 31 are implemented by software, firmware, or a combination of software and firmware. The software and firmware are written in the form of programs and stored in the memory 82. The processor 81 reads and executes the programs stored in the memory 82, thus achieving the above-described functions of the components. In other words, the memory 82 stores programs for executing the processing of the components of the short-circuit determination device 31.

[0030] Examples of memory 82 include non-volatile or volatile semiconductor memories such as random access memory (RAM), read-only memory (ROM), flash memory, erasable programmable read-only memory (EPROM), and electrically erasable programmable read-only memory (EEPROM), magnetic disks, floppy disks, optical disks, compact discs, minidiscs, and DVDs (digital versatile discs).

[0031] The short-circuit determination device 31 is connected to the current sensors CT1 and CT2, the circuit control device 12, and the circuit protection device 13 via the interface 83. The interface 83 includes interface modules that conform to one or more standards, depending on the connection targets.

[0032] The short-circuit determining device 31 having the configuration described above performs a short-circuit determining operation described below with reference to Fig. 4. In response to starting a travel of the rail vehicle and closing the circuit breaker 92, the short circuit determination device 31 initiates the Fig. 4 illustrated procedure or process.

[0033] The first current detecting means 32 detects a first current value which is a value of a current flowing into the primary winding 21, and the second current detecting means 33 detects a second current value which is a value of a current flowing out of the secondary winding 22 (step S11).

[0034] The short-circuit determining device 34 calculates a difference ΔD1 between the first current value I P and the current value on the primary side of the transformer 20, which is derived from the second current value I S1 is calculated using an expression (1) below (step S12). In detail, the short-circuit determining means 34 subtracts the product of the second current value IS1 and the inverse of the turns ratio N P / N S1 of the transformer 20 from the first current value I P and thus calculates a difference ΔD1. Expression 1 ΔD1=IP−IS1⋅NS1NP

[0035] The short-circuit determination means 34 determines whether the absolute value of the difference ΔD1 calculated in step S12 is at least the first threshold (step S13). If the absolute value of the difference ΔD1 calculated in step S12 is at least the first threshold (step S13; Yes), the short-circuit determination means 34 outputs a determination result indicating the occurrence of a short circuit to the circuit control means 12 and the circuit protection means 13 (step S14). In response to this result, the circuit control means 12 stops the power conversion circuit 11, and the circuit protection means 13 opens the circuit breaker 92. These operations cause the transformer 20, whose secondary winding 22 has a short circuit, to be electrically disconnected from the power source 91.After step S14, the short circuit determining device 31 repeats step S11 and the subsequent steps described above.

[0036] In contrast, if the absolute value of the difference ΔD1 calculated in step S12 is smaller than the first threshold (step S13; No), the short-circuit determining device 34 outputs a determination result indicating no short circuit to the circuit controller 12 and the circuit protecting device 13 (step S15). In response to this result, the circuit controller 12 continues operating the power converter circuit 11 according to an operation command. The circuit protecting device 13 does not open the protective switch 92 and continues to keep the protective switch 92 closed. After step S15, the short-circuit determining device 31 repeats step S11 and the subsequent steps described above.

[0037] As described above, the short circuit determination device 31 according to Embodiment 1 can determine whether a short circuit occurs in the secondary winding 22 of the transformer 20 based on the first current value and the second current value related to the primary side, which are calculated from the first current value, the second current value, and the turns ratio of the transformer 20. Embodiment 2

[0038] The configuration of the transformer 20 in Embodiment 1 is merely an example. The transformer 20 could, for example, include multiple secondary windings. The configuration of the short-circuit determination device 31 in Embodiment 1 is merely an example. The short-circuit determination device 31 could open the circuit breaker 92. The description of Embodiment 2 demonstrates the transformer 20 and the short-circuit determination device 31 with a configuration different from that of Embodiment 1, focusing on the differences from Embodiment 1.

[0039] As in Fig. 5, in Embodiment 2, the transformer 20 includes a primary winding 21 and a plurality of secondary windings, specifically, secondary windings 22 and 23. The secondary winding 22 is electrically connected to a power conversion device 1, as in Embodiment 1. The secondary winding 23 is electrically connected to a power conversion device 2. The transformer 20 transforms the voltage of AC power supplied from the power source 91 to the primary winding 21 via the circuit breaker 92, and outputs the AC power after voltage transformation from the secondary winding 22 to the power conversion device 1, and outputs the AC power after voltage transformation from the secondary winding 23 to the power conversion device 2.

[0040] The power conversion device 2 converts the AC power supplied from the power source 91 via the circuit breaker 92 and transformed by the transformer 20 into AC power to be supplied to a load device, specifically, a motor 94, and supplies the converted AC power to the motor 94. A typical example of the motor 94 is a three-phase induction motor for generating a driving force of the railway vehicle.

[0041] The power converter device 2 comprises a power converter circuit 14 whose primary terminals are electrically connected to the secondary winding 23 and whose secondary terminals are electrically connected to the motor 94, and a circuit controller 15 that controls the power converter circuit 14.

[0042] The power converter circuit 14 converts the AC power supplied from the secondary winding 23 through the primary terminals into three-phase AC power to be supplied to the motor 94, and then supplies the three-phase AC power from the secondary terminals to the motor 94. For example, the power converter circuit 14 includes a converter that converts the AC power supplied from the secondary winding 23 into DC power and outputs the DC power, a capacitor that is charged with the DC power output from the converter, and an inverter that converts the DC power supplied from the converter through the capacitor into three-phase AC power.

[0043] Both the converter and the inverter comprise several switching elements, such as IGBTs, GTOs, or MOSFETs. The switching elements perform switching operations, thus enabling the converter and the inverter to perform power conversion.

[0044] The circuit control device 15 controls the switching elements included in the power converter circuit 14 according to an operation command for the railway vehicle obtained from the driver's cab and a result of a determination by the short-circuit determination device 31. For example, the circuit control device 15 transmits PWM signals to the individual gate terminals of the IGBTs of the converter and the inverter, thus controlling the IGBTs.

[0045] While the railway vehicle is running, the circuit control device 15 controls the power converter circuit 14 according to an operation command. The circuit control device 15 stops the power converter circuit 14 when it receives a determination result indicating the occurrence of a short circuit in the transformer 20 from the short circuit determination device 31.

[0046] The power conversion devices 1 and 2 both exclude the short-circuit determination device 31 and the circuit protection device 13, unlike the power conversion device 1 according to Embodiment 1.

[0047] In Embodiment 2, the short-circuit determination device 31 is an independent device separated from the power conversion devices 1 and 2. The second current detection means 33 of the short-circuit determination device 31 detects second current values, which are values ​​of a current flowing from the respective secondary windings 22 and 23. In other words, the second current detection means 33 measures a second current value of the secondary winding 22, which is a value of a current flowing in the electrical path between the secondary winding 22 and the power conversion circuit 11, and a second current value of the secondary winding 23, which is a value of a current flowing in the electrical path between the secondary winding 23 and the power conversion circuit 14.

[0048] In detail, the second current detecting device 33 measures second current values ​​of the secondary windings 22 and 23 with a CT-type current sensor CT2 provided for the conductor connecting one end of the secondary winding 22 to one of the primary terminals of the power converter circuit 11 and with a CT-type current sensor CT3 provided for the conductor connecting one end of the secondary winding 23 to one of the primary terminals of the power converter circuit 14.

[0049] The short-circuit determination device 34 determines whether a short circuit occurs in the secondary windings 22 and 23 based on the first current value and the second current values ​​related to the primary side, which are calculated from the first current value, the second current value, the number of turns of the primary winding 21, and the number of turns of the respective secondary windings 22 and 23. It is assumed that the short-circuit determination device 34 preliminarily stores information about the number of turns of the primary winding 21 and the number of turns of the respective secondary windings 22 and 23.

[0050] As an exemplary anomaly, a short circuit could occur in at least one of the secondary windings 22 and 23. For example, a short circuit could occur in the secondary winding 22. More specifically, this means that the conductor connecting one end of the secondary winding 22 to one of the primary terminals of the power converter circuit 11 could be electrically directly connected to the conductor connecting the other end of the secondary winding 22 to the other of the primary terminals of the power converter circuit 11. This direct connection allows a current to flow through a closed circuit defined by the secondary winding 22.In the case of a short circuit in a position closer to the secondary winding 22 than the current sensor CT2, no current flows in the current sensor CT2, so that the second current value of the secondary winding 22 to be detected by the second current detecting means 33 is sufficiently smaller than that in the case of no short circuit in the secondary winding 22.

[0051] As another example, a short circuit could occur in the secondary winding 23. More specifically, this means that the conductor connecting one end of the secondary winding 23 to the power converter circuit 14 could be electrically directly connected to the conductor connecting the other end of the secondary winding 23 to the power converter circuit 14. This direct connection allows a current to flow through a closed circuit defined by the secondary winding 23. In the case of a short circuit at a position closer to the secondary winding 23 than the current sensor CT3, no current flows into the current sensor CT3, so that the second current value of the secondary winding 23 to be detected by the second current detecting device 33 is sufficiently smaller than that in the case of no short circuit in the secondary winding 23.

[0052] Due to such a small sum of the second current values ​​in the event of a short circuit in at least one of the secondary windings 22 and 23 described above, the short-circuit determining device 34 determines whether a short circuit occurs in at least one of the secondary windings 22 and 23 based on the difference between the first current value and the second current values ​​related to the primary side—more specifically, current values ​​on the primary side of the transformer 20 calculated from the second current values. If the absolute value of the difference between the first current value and the current value on the primary side of the transformer 20 calculated from the second current values ​​is at least the first threshold, it is assumed that a short circuit occurs in at least one of the secondary windings 22 and 23.In contrast, if the absolute value of the difference between the first current value and the current value on the primary side of the transformer 20 calculated from the second current value is smaller than the first threshold, it is assumed that no short circuit occurs in the secondary windings 22 and 23.

[0053] The short-circuit determination device 31 also includes, in addition to the components of the short-circuit determination device 31 according to Embodiment 1, a circuit protection device 35 that controls the circuit breaker 92. The circuit protection device 35 closes or opens the circuit breaker 92 according to a determination result by the short-circuit determination device 34. In detail, the circuit protection device 35 keeps the circuit breaker 92 closed while the short-circuit determination device 34 continues to determine that no short circuit occurs in the secondary windings 22 and 23. When the short-circuit determination device 34 determines that a short circuit occurs in at least one of the secondary windings 22 and 23, the circuit protection device 35 opens the circuit breaker 92 and electrically disconnects the primary winding 21 of the transformer 20 from the power source 91.

[0054] The short-circuit determination device 31 has the hardware components identical to those in Embodiment 1 except for the connection destinations via the interface 83. In Embodiment 2, the interface 83 is connected to the current sensors CT1, CT2, and CT3 and the circuit control devices 12 and 15.

[0055] The short-circuit determining device 31 having the configuration described above performs a short-circuit determining operation described below with reference to Fig. 6. In response to starting to travel the rail vehicle and closing the circuit breaker 92, the short circuit determination device 31 initiates the Fig. 6 illustrated process.

[0056] The first current detecting means 32 detects a first current value which is a value of a current flowing into the primary winding 21, and the second current detecting means 33 detects second current values ​​which are values ​​of a current flowing out of the respective secondary windings 22 and 23 (step S21).

[0057] The short-circuit determination device 34 calculates a difference ΔD2 between the first current value and the current value on the primary side of the transformer 20 calculated from the second current value using expression (2) below (step S22). In detail, the short-circuit determination device 34 subtracts the sum of the second current value I S1 , which is the number N S1 of turns of the secondary winding 22 and which is multiplied by the number N P of the turns of the primary winding 21, and the second current value I S2 , which is the number of turns N S2the secondary winding 23 and which is multiplied by the number N P of turns of the primary winding 21 is divided by the first current value I P and thus calculates a difference ΔD2. The second current value I S1 indicates a value of a current flowing from the secondary winding 22, and the second current value I S2 indicates a value of a current flowing from the secondary winding 23. Expression 2 ΔD2=IP−(IS1⋅NS1NP+IS2⋅NS2NP)

[0058] The short-circuit determination means 34 determines whether the absolute value of the difference ΔD2 calculated in step S22 is at least the first threshold (step S23). If the absolute value of the difference ΔD2 calculated in step S22 is at least the first threshold (step S23; Yes), the short-circuit determination means 34 outputs a determination result indicating the occurrence of a short circuit to the circuit control means 12 and 15 and the circuit protection means 35 (step S24). In response to this result, the circuit control means 12 and 15 stop the power converter circuits 11 and 14.

[0059] When the circuit protection device 35 receives a determination result indicating the occurrence of a short circuit, it opens the circuit breaker 92 (step S25). After step S25, the short circuit determination device 31 repeats step S21 and the subsequent steps described above.

[0060] In contrast, if the absolute value of the difference ΔD2 calculated in step S22 is smaller than the first threshold (step S23; No), the short-circuit determining device 34 outputs a determination result indicating no short circuit to the circuit control devices 12 and 15 and the circuit protection device 35 (step S26). In response to this result, the circuit control devices 12 and 15 continue operating the power converter circuits 11 and 14 according to an operation command. The circuit protection device 35 skips step S25, more specifically, it does not open the circuit breaker 92 and continues to keep the circuit breaker 92 closed. After step S26, the short-circuit determining device 31 repeats step S21 and the subsequent steps described above.

[0061] As described above, the short-circuit determining device 31 according to Embodiment 2 can determine whether a short circuit occurs in the secondary windings 22 and 23 based on the first current value, the second current value, the number of turns of the primary winding 21, and the numbers of turns of the respective secondary windings 22 and 23, and can electrically disconnect the transformer 20 from the power source 91 in the event of a short circuit in the secondary winding 22 or 23.

[0062] The above-described embodiments of the present disclosure are merely examples. The power conversion devices 1 and 2 can be installed in any vehicle or device in which the power conversion devices 1 and 2 are supplied with electric power. The power conversion devices 1 and 2 can also be installed in vehicles, such as diesel vehicles, other than the electric rail vehicle.

[0063] The transformer 20 could have a configuration different from that described in the examples above. The transformer 20 could include any number of secondary windings. The secondary windings included in the transformer 20 could have the same number of turns or a different number of turns.

[0064] The short-circuit determination process performed by the short-circuit determination device 34 could be a process different from those in the examples described above. For example, the short-circuit determination device 34 could determine whether a short circuit occurs in the secondary winding 22 based on a first current value related to the secondary side and a second current value. In detail, the short-circuit determination device 34 could determine a difference ΔD1' between a current value on the secondary side of the transformer 20, which is derived from the first current value I P is calculated, and the second current value I S1 using an expression (3) below. In detail, the short-circuit determining means 34 could calculate the second current value I S1 of the product of the first current value I P with the turns ratio N P / N S1of the transformer 20 and thus calculate a difference ΔD1'. Expression 3 ΔD1'=IP⋅NPNS1−IS1

[0065] In this case, the short-circuit determination device 34 determines whether the absolute value of the difference ΔD1' is at least a second threshold. The second threshold is defined in accordance with a possible range of an amplitude of a current flowing from the secondary winding 22. For example, the second threshold is a value calculated by multiplying the lower limit of the possible range of an amplitude of a current flowing from the secondary winding 22 by a positive coefficient less than 1, for example, 0.5. It is assumed that the short-circuit determination device 34 temporarily stores information about the second threshold.

[0066] In another exemplary case where a plurality of secondary windings included in the transformer 20 have the same number of turns, the short-circuit determining means 34 of the short-circuit determining device 31 according to Embodiment 2 may determine whether a short circuit occurs in each of the secondary windings based on the first current value, the second current value, the number of turns of the primary winding 21, and the number of turns of the secondary winding.

[0067] In detail, the short-circuit determination device 34 calculates a difference ΔD3 between the first current value and a current value on the primary side of the transformer 20 calculated from each of the second current values ​​using Expression (4) below. In Expression (4) below, M indicates the number of secondary windings included in the transformer 20, and N Sindicates the number of turns of the secondary winding. k indicates a natural number that is greater than or equal to 1 and less than or equal to M, and I Sk indicates a second current value, which is a value of a current flowing from each of the secondary windings. Expression 4 ΔD3=IP−ISk⋅NSNP⋅M

[0068] The short-circuit determination device 34 calculates a difference ΔD3 for each of the secondary windings and determines whether the absolute value of the difference ΔD3 is at least the first threshold. If the absolute value of the difference ΔD3 is at least the first threshold in one of the secondary windings, it is assumed that a short circuit has occurred in that secondary winding.

[0069] Alternatively, if the short-circuit determining device 34 determines that a short circuit is occurring in at least one of the secondary windings, it could determine whether a short circuit is occurring in each of the secondary windings based on the second current values ​​of the secondary windings. More specifically, this means that the short-circuit determining device 34 could determine whether the second current value of each of the secondary windings has an amplitude falling within a range of values ​​sufficiently small to be considered 0. In the case of a short circuit, a current value detectable by a current sensor is sufficiently small, as described above.The short circuit determining means 34 thus determines whether a short circuit occurs in each of the secondary windings based on whether the second current value of each of the secondary windings has an amplitude falling within a range of values ​​sufficiently small to be considered 0.

[0070] Alternatively, the short-circuit determining device 34 could determine whether a short circuit occurs in the secondary winding based on the ratio of the second current value related to the primary side to the original second current value, or the ratio of the first current value related to the secondary side to the original first current value. More specifically, this means that the short-circuit determining device 34 could determine whether a short circuit occurs in the secondary winding 22 based on the ratio of the current value on the primary side of the transformer 20, calculated from the second current value, to the first current value. If the absolute value of the ratio of the current value on the primary side of the transformer 20, calculated from the second current value, to the first current value is less than or equal to a third threshold, it is assumed that a short circuit occurs in the secondary winding 22.The third threshold is a positive value less than 1, for example, 0.5. It is assumed that the short-circuit determination device 34 temporarily stores information about the third threshold.

[0071] Alternatively, the short-circuit determination device 34 could determine whether a short circuit is occurring in the secondary winding 22 based on the ratio of the current value on the secondary side of the transformer 20, calculated from the first current value, to the second current value. If the ratio of the current value on the secondary side of the transformer 20, calculated from the first current value, to the second current value is less than or equal to the third threshold, it is assumed that a short circuit is occurring in the secondary winding 22.

[0072] The electronic device connected to the transformer 20 is not necessarily the power converter device 1 or 2 and could be any electronic device.

[0073] The power converter devices 1 and 2 could supply electrical power to any load device, such as a lighting system or an air conditioner, other than the motors 93 and 94.

[0074] Current sensors CT1, CT2, and CT3 could be arranged in positions different from those in the examples described above. For example, current sensor CT1 could be provided for the conductor connected to the other end of primary winding 21. Current sensor CT2 could be provided for the conductor connecting the other end of secondary winding 22 to the other of the primary terminals of power converter circuit 11. Current sensor CT3 could be provided for the conductor connecting the other end of secondary winding 23 to power converter circuit 14.

[0075] The first current detecting means 32 may obtain an amplitude of a current flowing into the primary winding 21 from the measured value of a current flowing into the primary winding 21 and use this amplitude as the first current value.

[0076] The second current detection device 33 could obtain an amplitude of a current flowing out of the secondary winding 22 from the measured value of a current flowing out of the secondary winding 22 and use this amplitude as a second current value of the secondary winding 22. The second current detection device 33 could obtain an amplitude of a current flowing out of the secondary winding 23 from the measured value of a current flowing out of the secondary winding 23 and use this amplitude as a second current value of the secondary winding 23.

[0077] Although the circuit protection device 13 is included in the power conversion device 1 in Embodiment 1, the circuit protection device 13 could also be achieved as a function of an integrated train control and monitoring device.

[0078] Although the short-circuit determination device 31 is separated from the power conversion devices 1 and 2 in Embodiment 2, the short-circuit determination device 31 could also be included in the power conversion device 1 or 2. Alternatively, the short-circuit determination device 31 could be achieved as a function of a train control and monitoring device.

[0079] The short-circuit determination device 31 could have hardware components that differ from those in the examples described above. The short-circuit determination device 31 could be achieved by a processing circuit 84, as shown in Fig. 7. The processing circuit 84 is connected to the current sensors CT1 and CT2, the circuit control device 12, and the circuit protection device 13 via an interface circuit 85.

[0080] In the case where the processing circuit 84 is dedicated hardware, the processing circuit 84 comprises, for example, a single circuit, a combined circuit, a processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof. The individual components of the short-circuit determination device 31 could be achieved by separate processing circuits 84 or by the same processing circuit 84.

[0081] Part of the functions of the short-circuit determination device 31 could be performed by dedicated hardware, whereas other parts of the functions could be performed by software or firmware. For example, the first current detection device 32 and the second current detection device 33 could be achieved by the processing circuit 84 included in Fig. 7, whereas the short-circuit determination means 34 could be achieved by programs stored in the memory 82 if the programs are executed by the processor 81, which is shown in Fig. 3, in the short circuit determination device 31 according to Embodiment 1.

[0082] The foregoing describes some exemplary embodiments for illustrative purposes. Although the foregoing discussion has presented specific embodiments, those skilled in the art will recognize that changes in form and detail may be made without departing from the broader spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive. This detailed description, therefore, is not to be taken in a limiting sense, and the scope of the invention is defined only by the claims appended hereto, along with the full range of equivalents to which such claims are entitled. List of reference symbols 1, 2 Power converter device 11, 14 Power converter circuit 12, 15 Circuit control device 13, 35 Circuit protection device 20 Transformer 21 Primary winding 22, 23 Secondary winding 31 Short-circuit detection device 32 First current measuring device 33 Second current measuring device 34 Short-circuit determination device 80 buses 81 processor 82 storage 83 Interface 84 processing circuit 85 Interface circuit 91 Power source 92 circuit breakers 93, 94 engine CT1, CT2, CT3 current sensor QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 6-141404

[0003]

Claims

[1] Short-circuit detection device comprising: a first current detecting device for detecting a first current value, the first current value being a value of a current flowing into a primary winding of a transformer, the transformer transforming a voltage of an AC power supplied to the primary winding and outputting the AC power after voltage transformation from one or more secondary windings of the transformer; a second current detecting means for detecting a second current value, wherein the second current value is a value of a current flowing from each of the one or more secondary windings; and a short-circuit determining device for determining, based on the first current value and a second current value relating to a primary side, or a first current value relating to a secondary side and the second current value, whether a short circuit occurs in each of the one or more secondary windings, wherein the second current value relating to the primary side and the first current value relating to the secondary side are calculated from the first current value, the second current value, a number of turns of the primary winding, and a number of turns of each of the one or more secondary windings. [2] The short-circuit determining device according to claim 1, wherein the first current detecting means measures the first current value, the first current value being a value of a current flowing in an electrical path between a power source and the primary winding, the power source supplying electric power to the transformer. [3] The short-circuit determining device according to claim 1 or 2, wherein the second current detecting means measures the second current value, the second current value being a value of a current flowing in an electrical path between each of the one or more secondary windings and an electronic device electrically connected to the secondary winding. [4] Short circuit determining device according to one of claims 1 to 3, wherein the one or more secondary windings of the transformer comprise the single secondary winding, the second current detecting means detects a second current value, wherein the second current value is a value of a current flowing from the secondary winding, and the short-circuit determining means determines whether a short circuit occurs in the secondary winding based on the first current value and the second current value relating to the primary side, or the first current value relating to the secondary side and the second current value, wherein the second current value relating to the secondary side and the first current value relating to the secondary side are calculated from the first current value, the second current value and a turns ratio of the transformer. [5] Short circuit determining device according to one of claims 1 to 3, wherein the one or more secondary windings of the transformer comprise a plurality of secondary windings, the second current detecting means detects second current values, the second current values ​​being values ​​of a current flowing from the plurality of secondary windings, and the short-circuit determining means determines, based on the first current value and the second current values ​​relating to the primary side, whether a short circuit occurs in at least any of the plurality of secondary windings, wherein the second current values ​​relating to the primary side are calculated from the first current value, the second current values ​​of the plurality of secondary windings, the number of turns of the primary winding, and the numbers of turns of the plurality of secondary windings. [6] The short-circuit determining device according to claim 5, wherein, when the short-circuit determining means determines that a short-circuit occurs in at least any one of the plurality of secondary windings, the short-circuit determining means determines whether a short-circuit occurs in each of the plurality of secondary windings based on the second current values ​​of the plurality of secondary windings. [7] Short circuit determining device according to one of claims 1 to 3, wherein the one or more secondary windings of the transformer comprise a plurality of secondary windings having an equal number of turns, the second current detecting means detects second current values, the second current values ​​being values ​​of a current flowing from the plurality of secondary windings, and for each of the plurality of secondary windings, the short-circuit determining means determines whether a short circuit occurs in the secondary winding based on the first current value and the second current value relating to the primary side, or on the first current value relating to the secondary side and the second current value, wherein the second current value relating to the primary side and the first current value relating to the secondary side are calculated from the first current value, the second current value of each of the plurality of secondary windings, the number of turns of the primary winding, and the numbers of turns of the secondary winding. [8] A short circuit determining device according to any one of claims 1 to 7, further comprising: a circuit protection device for electrically isolating the primary winding from a power source when the short-circuit determining device determines that a short circuit occurs, the power source supplying electrical power to the primary winding of the transformer. [9] An electronic device electrically connected to each of one or more secondary windings of a transformer, the transformer transforming a voltage of AC power supplied to a primary winding of the transformer and outputting the AC power after voltage transformation from the one or more secondary windings, the electronic device comprising: the short-circuit determining device according to any one of claims 1 to 7 for determining whether a short circuit occurs in the one or more secondary windings of the transformer. [10] The electronic device of claim 9, further comprising: a circuit protection device for electrically disconnecting the primary winding from a power source when the short-circuit determining device determines that a short circuit occurs, the power source supplying electrical power to the primary winding of the transformer. [11] An electronic device electrically connected to each of one or more secondary windings of a transformer, the transformer transforming a voltage of AC power supplied to a primary winding of the transformer and outputting the AC power after voltage transformation from the one or more secondary windings, the electronic device comprising: the short-circuit determining device according to claim 8 for determining whether a short circuit occurs in the one or more secondary windings of the transformer. [12] Electronic device according to one of claims 9 to 11, further comprising: a power converter circuit electrically connected to each of one or more secondary windings of the transformer, the power converter circuit configured to convert the AC power output from the connected one of the one or more secondary windings into electrical power to be supplied to a load device and output the converted electrical power to the load device. [13] The electronic device of claim 12, further comprising: a circuit control device configured to control the power converter circuit, wherein the circuit control means stops the power converter circuit when the short-circuit determining means determines that a short circuit occurs. [14] A method for determining a short circuit, the method comprising: Detecting a first current value, the first current value being a value of a current flowing into a primary winding of a transformer, the transformer transforming a voltage of AC power to be supplied to the primary winding and outputting the AC power after voltage transformation from one or more secondary windings of the transformer; Detecting a second current value, wherein the second current value is a value of a current flowing from each of the one or more secondary windings; and Determining, based on the first current value and a second current value relating to a primary side, or on a first current value relating to a secondary side and the second current value, whether a short circuit occurs in each of the one or more secondary windings, wherein the second current value relating to the primary side and the first current value relating to the secondary side are calculated from the first current value, the second current value, a number of turns of the primary winding, and a number of turns of each of the one or more secondary windings.

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