Patent Description:
For a drive device for driving a motor for a rail vehicle, a three-phase AC motor is widely used. In recent years, the application of a permanent magnet synchronous motor (hereinafter abbreviated as "PMSM" in some cases) as a three-phase AC motor has been promoted for the purpose of downsizing a drive system for a rail vehicle and improving the efficiency of the drive system.

When the PMSM rotates, an induced voltage occurs between terminals of the motor due to a magnetic flux of a permanent magnet. Therefore, when a rail vehicle is continuously operated in a state in which a short circuit failure or the like occurs in an inverter device for driving the PMSM, a short circuit current continuously flows in the inverter device due to the induced voltage of the PMSM and a braking force occurs in the PMSM.

When one inverter device is in such a state, acceleration performance of the rail vehicle may decrease and the short circuit accident current may continuously flow to cause burnout of a device or the like. Therefore, a failure of one inverter device prevents the rail vehicle from being normally operated. In the drive device for driving the PMSM, motor cutout contacts (hereinafter abbreviated as "MCOKs") for electrically disconnecting the PMSM from the inverter device at the time of a failure of the inverter device may be provided.

In addition, an inverter device for driving a three-phase AC motor such as a PMSM inputs, to a control device, phase current information of a current detector that detects phase currents of three phases and inter-line voltage information of a voltage detector that detects a voltage between the three phases. The phase current information and the inter-line voltage information are used for control calculation for driving the three-phase AC motor by the inverter device and are used for protective detection to stop the inverter device or the like so as to ensure safety and prevent a failure of the device. As an example of this configuration, Patent Literature <NUM> and Patent Literature <NUM> disclose examples of circuit configurations for disconnecting a PMSM from an inverter device at the time of a failure of the device. Techniques relating to them are described at the end as Comparative Example <NUM> illustrated in <FIG> and Comparative Example <NUM> illustrated in <FIG>.

<CIT> revealed a drive projection device for protecting a traction drive in a vehicle, in particular a rail vehicle, comprising at least one switching unit having an activation position and a deactivation position that protects the traction drive, and comprising a control unit that is provided to trigger a transition into the deactivation position in at least a first operating situation when an operating variable of the drive is in a critical range.

The circuit configurations described in Patent Literature <NUM> and Patent Literature <NUM> have, for example, the following two problems.

First, when a short circuit failure occurs in a voltage detector (alternating current potential transformer: hereinafter abbreviated as "ACPT" in some cases) between phases, and a motor cutout contactor (MCOK) is in a released state (that is, an opened state), there is a problem that a current detector cannot detect an inter-phase short circuit current of the voltage detector. On the other hand, even when an inverter device and a motor, particularly a PMSM, are disconnected from each other, there is a demand for an ammeter attached or built on the inverter device side to detect a regenerative current generated by the motor.

Second, for a rail vehicle, the inverter device is installed under a floor of the vehicle in many cases. In such a case, there is a problem that it is desirable that the current.

detector and the ACPT be installed on the rear side (that is, at a position close to the motor) with respect to the MCOK as viewed from the inverter device. There are the following two reasons, for example. One is that the current detector and the ACPT may not be able to be installed in the inverter device due to a dimensional limit on a drive device such as the inverter device. The other one is that it is desirable that the current detector and the ACPT be installed on the rear side of the MCOK in a case in which the MCOK is retrofitted in the inverter device or the like from the perspective of the installation position of the current detector in the existing inverter device.

<CIT> discloses a three-phase AC motor drive device that drives a load, comprising an inverter, a motor cutout contact configured to electrically connect or disconnect the inverter device to or from the load; a voltage detector configured to detect a voltage between three phases and having terminals connected to circuits of at least two of the phases;a current detector configured to detect phase currents of the three phases; and a control device for the inverter.

The foregoing problems may occur even when, for example, compatibility of a drive system using an induction motor as a three-phase AC motor with a drive system using a PMSM is ensured to save labor and achieve simplification. For actual rail vehicles, replacement of existing induction motors with PMSMs is sequentially promoted.

To solve the foregoing problems, according to the present invention, a three-phase AC motor drive device that drives a load flowing toward a direction opposite to the one direction, and is configured to convert direct-current power supplied from a power supply into three-phase alternating-current power and drive the load; a motor cutout contact configured to electrically connect or disconnect the inverter device to or from the load; a voltage detector configured to detect a voltage between three phases and having terminals connected to circuits of at least two of the phases; and a current detector configured to detect phase currents of the three phases ; and a control device configured to acquire detection output of the voltage detector and control a switching operation of each current control element of the inverter device based on the detection output such that an AC motor outputs desired torque; in a connection from the inverter device to the load, the inverter device, the motor cutout contact, the voltage detector, the current detector, and the load are arranged in this order; wherein in a circuit of one of the two phases connected to the voltage detector, the motor cutout contact is connected to a connection point of the voltage detector and the current detector, in a circuit of the other phase, the motor cutout contact is connected to the inverter device and a connection point of the voltage detector; and in a phase in which a first motor cutout contact is disposed between the inverter device and a connection point of the voltage detector, a second motor cutout contact is connected to the connection point of the voltage detector and the current detector.

In the phase-three AC motor drive device according to the present invention, when a short circuit failure occurs in the voltage detector, the motor cutout contact is released. Releasing the motor cutout contact electrically disconnects the inverter device from the AC motor. Even in this state, the current detector can detect a short circuit current flowing in a path between the load and the voltage detector.

The case in which the motor cutout contact is released corresponds to a case in which the load of the three-phase AC motor drive device used in a rail vehicle is a permanent magnet synchronous motor and a failure such as a short circuit failure of the voltage detector or a reduction in output of the inverter device occurs. In such a case, a driver or the like may take optimal security measures to eliminate a regenerative braking action of the permanent magnet synchronous motor and continuously operate the vehicle with other remaining power.

In addition, when the load is changed from an induction motor to a permanent magnet synchronous motor, basic design may be made such that the motor cutout contact required to avoid a regenerative braking action caused at the time of the foregoing failure, and the voltage detector are disposed in the immediate vicinity of the inverter device in this order. To secure a space for the motor cutout contact, the current detector is disposed in the immediate vicinity of the load while avoiding the space. In other words, even in a case in which the motor cutout contact is not required in the inverter device at the initial design stage, when the space is secured, and the motor cutout contact needs to be retrofitted, there is no trouble. That is, it is easy to secure the installation configuration of the inverter device and compatibility of device arrangement, regardless of whether the motor cutout contact is present.

As an example of the present invention, Example <NUM> is described below with reference to drawings. A three-phase AC motor drive device according to the embodiment of the present invention is abbreviated as a present device, while a three-phase AC motor drive device according to a comparative example is abbreviated as a comparative device.

<FIG> is a configuration diagram illustrating an example of a present device <NUM> according to Example <NUM>. An inverter device <NUM> is constituted by a current control element that can conduct or block a current flowing from a high-pressure side to a low-pressure side, and a diode that can conduct a current flowing toward a direction opposite to the one direction.

As the current control element, a power semiconductor element such as an insulated gate bipolar transistor (IGBT) or a power metal oxide semiconductor field effect transistor (MOSFET) is used in general.

Silicon is used as a material of these power semiconductor elements in many cases. However, in recent years, power semiconductor elements in which SiC (silicon carbide) or GaN (gallium nitride) is used have been increasing in number to contribute to reductions in system losses. Therefore, SiC or GaN may be used in the current control element used in the inverter device <NUM> according to the present invention.

The inverter device <NUM> converts direct-current power output from a direct-current power supply not illustrated into three-phase alternating-current power and drives an AC motor <NUM>. The direct-current power supply that inputs power to the inverter device <NUM> is a direct-current power supply input unit for the inverter device. A smoothing capacitor <NUM> is connected to the inverter device <NUM> in parallel. The inverter device <NUM> is connected to the higher-level direct-current power supply via the smoothing capacitor <NUM>. The AC motor <NUM> is described as a load in some cases.

As the AC motor <NUM>, an induction motor, a PMSM_2', or the like is used. Although <FIG> illustrates that the inverter device <NUM> is configured to drive the single AC motor <NUM>, the inverter device <NUM> may be configured to drive a plurality of AC motors <NUM>. In some drawings, the PMSM_2' is indicated by a reference sign <NUM>' to distinguish them.

ACPTs_11a to 11c that detect current values of phases and MCOKs_A_4a to 4c are provided on the alternating-current output side of the inverter device <NUM>. The MCOKs_A_4a to 4c are collectively referred to as MCOKs_A_4, while the ACPTs_11a to 11c are collectively referred to as ACPTs_11. A control device <NUM> acquires detection output of the ACPTs_11 and controls a switching operation of each current control element of the inverter device <NUM> based on the detection output such that the AC motor <NUM> outputs desired torque.

When current values detected by the ACPTs_11 are abnormally high or the like, the inverter device <NUM> may be stopped or the MCOKs_A_4 may be released to electrically disconnect the inverter device <NUM> from the AC motor <NUM> for device protection and safety.

In accordance with a release instruction output from the control device <NUM>, the MCOKs_A_4 connect or disconnect main circuit contacts that electrically connect the three phases of the inverter device <NUM> and the AC motor <NUM>. A configuration for turning on and releasing for each phase or a configuration for turning on and releasing in coordination with the plurality of phases may be provided.

In addition, the ACPTs_11 may be only the two ACPTs_11a and 11c disposed in two of the phases, for example. That is, it is not necessary to detect currents of all the three phases. A configuration for detecting currents in two of the three phases and calculating a current of the remaining one phase while assuming that three-phase currents are in equilibrium may be provided.

An ACPT_21a is provided between phases (U and V phases in the example of <FIG>) on the alternating-current output side of the inverter device <NUM> and on the AC motor <NUM> side and detects a voltage between the phases, that is, a voltage between terminals of the AC motor. When the control device <NUM> or the like acquires a detection signal of the ACPT_21a and the AC motor <NUM> is the PMSM_2' or the like, the control device <NUM> or the like controls output of the inverter device <NUM> after confirming the voltage between the terminals, thereby being able to start an operation as an inverter in a stable manner.

In this case, the inverter device <NUM>, the AC motor <NUM>, the MCOKs_A_4, the current detectors <NUM>, and the ACPT_21a are connected in the order of the inverter device <NUM>, the MCOKs_A_4, the ACPT_21a, the current detectors 11a to 11c, and the AC motor <NUM>.

The present device <NUM> has the foregoing connection configuration. Therefore, even when the MCOKs_A_4 are released to disconnect the inverter device <NUM> from the AC motor <NUM>, and the ACPT_21a has a short circuit failure (short circuit between the U phase and the V phase in <FIG>), the current detectors 11a and 11b can detect a short circuit current flowing in a path extending from the AC motor <NUM> to the ACPT_21a.

In addition, even when not only the short circuit failure of the ACPt_21a occurs but also a short circuit occurs between phases due to burnout of the AC motor <NUM> or a wiring coil or insulation deterioration in the present device <NUM>, a driver or the like can detect the short circuits. The present device <NUM> is, for example, suitable to be used as a drive device for a rail vehicle or the like. In the case of the use, when such a short circuit current is detected, and all the MCOKs_A_4 are released, information indicating that the short circuit current flows can be given to a higher-level device such as a vehicle cab. When the information is given to the vehicle cab, the driver or the like can take security measures based on the information. Specifically, it is also possible to stop operating a corresponding vehicle and prevent a device failure from spreading.

<FIG> is a configuration diagram illustrating a present device <NUM> according to a modification in which the connection form of the ACPT_21a is different from the present device <NUM> illustrated in <FIG> illustrates the example in which the ACPT_21a is connected at a single position between the U phase and the V phase. However, as illustrated in <FIG> (not illustrating the control device <NUM>), a configuration in which the voltage detector (ACPT_21a) is connected between the U phase and the V phase and a voltage detector (ACPT_21b) is connected between the V phase and the W phase, that is, a configuration in which voltage detectors are connected at two or more positions between the phases, may be provided.

<FIG> are configuration diagrams exemplifying different inverter units <NUM> to explain the present device <NUM> according to Example <NUM>. <FIG> illustrates that only the current detectors <NUM> are interposed (connected) in the phases, while <FIG> illustrates that the current detectors <NUM> and the MCOKs are interposed in the phases and the ACPT_21a is disposed between the phases. In addition, <FIG> illustrates an example of a unit configuration of a general drive device for a rail vehicle, and the smoothing capacitor <NUM>, the inverter device <NUM>, and the current detectors <NUM> are disposed in the inverter unit <NUM> by a housing or the like. Since a three-phase induction motor is used as the AC motor <NUM> in a conventional drive device for a rail vehicle, the inverter unit <NUM> is constituted mainly in a portion surrounded by a dotted-line frame illustrated in <FIG>. Note that "interposed" indicates "connected to a circuit".

In recent years, there has been a rail vehicle in which the PMSM_2' is used as the AC motor <NUM> to downsize the foregoing drive system and improve the efficiency of the drive system. In this case, as illustrated in <FIG>, the smoothing capacitor <NUM>, the inverter device <NUM>, the current detector 11c, and the ACPT_21a are provided in the inverter unit <NUM>.

In particular, while the dimensions and shape of the housing for the inverter unit <NUM> are maintained and compatibility with a vehicle using an induction motor as a conventional AC motor <NUM> is maintained, the AC motor <NUM> may be replaced with the PMSM_2'. For example, to update the drive device for the rail vehicle or the like, an additional MCOK_A_4 and an additional ACPT_21a are provided as built-in devices in the inverter unit <NUM>. In this case, the following problem with installation occurs.

<FIG> are schematic diagrams of the arrangement of inverter units in rail vehicles. <FIG> illustrates a comparative example, <FIG> illustrates a comparative device 61b obtained by adding an MCOK to (a), and <FIG> illustrates installation simplified with the present device <NUM> illustrated in <FIG>, <FIG>, and <FIG>. <FIG> illustrates an example of an overview of installation of the inverter unit <NUM> in the rail vehicle and illustrates an example of the arrangement of devices in the conventional inverter unit <NUM>.

As illustrated in a lower part of <FIG>, in the conventional rail vehicle, a current detector <NUM> may be arranged near a terminal for external output in the inverter unit <NUM> due to a limit on a device implementation space within the inverter unit <NUM>. As described above, when the AC motor <NUM> is replaced with the PMSM_2', an additional MCOK_4 and an additional current detector 21a are provided. In this case, when the order in which devices are connected is the same as the conventional order illustrated in <FIG>, the devices are connected in the order of the inverter device <NUM>, the current detectors <NUM>, and the MCOKs_4. As a result, as indicated by the comparative device 61b illustrated in <FIG>, the installation within the inverter unit <NUM> becomes complex.

On the other hand, when the inverter device <NUM>, the MCOKs_4, and the current detectors <NUM> are connected in this order, like the present device <NUM> according to Example <NUM> illustrated in <FIG>, the installation within the inverter unit <NUM> can be simplified as indicated with the present device 61c illustrated in <FIG>. Therefore, it is possible to simplify the replacement of the AC motor <NUM> with the PMSM_2' while the dimensions and shape of the housing for the inverter unit <NUM> and compatibility with a vehicle using an induction motor as a conventional AC motor <NUM> are maintained, and an effect of saving labor is exhibited.

Next, Example <NUM> according to the present invention is described with reference to <FIG> is a configuration diagram of a present device <NUM> according to Example <NUM>. The present device <NUM> according to Example <NUM> illustrated in <FIG> is different from the present device <NUM> according to Example <NUM> in that one connection terminal of the ACPT_21a is connected between the inverter device <NUM> and the MCOK_A-4a in a U phase circuit.

With this configuration, the present device <NUM> according to Example <NUM> illustrated in <FIG> can block the foregoing short circuit current. Regarding this, even in a configuration in which a single MCOK_A is interposed in each phase in the present device <NUM>, when the ACPT_21a has a short circuit failure, a short circuit current flows between the ACPT_21a and the AC motor <NUM>. The short circuit current is detected by the current detectors 11a and 11b and input to the control device <NUM>.

When the short circuit current is input to the control device <NUM>, for example, a driver can manually take security measures at an electric vehicle cab or the control device <NUM> can automatically take security measures. That is, when this short circuit current is equal to or larger than a predetermined current value, the control device <NUM> outputs a release instruction to the MCOKs_A_4a to 4c (particularly, 4a and 4b in the case of <FIG>). Therefore, the MCOKs_A_4a to 4c (particularly, 4a and 4b in the case of <FIG>) can be released to block the short circuit current.

<FIG> only illustrates the example of the configuration of the present device <NUM>. That is, the one connection point (terminal) of the voltage detector <NUM> is connected between the inverter device <NUM> and the MCOK_A_4 in the U phase circuit. In addition, the other connection terminal (terminal) of the ACPT_21a is connected between the MCOK <NUM>4b and the current detector 11b in a V phase circuit.

In the example of the configuration, the connection relationship between the U phase and the V phase may be reversed. That is, one connection point of the ACPT_21a connected to two of the three phases may be connected between the inverter device <NUM> and the MCOK_A and the other connection point may be connected to the MCOK A and the current detector.

Next, Example <NUM>, which corresponds to an embodiment of the present invention is described with reference to <FIG> is a configuration diagram of a present device <NUM> according to Example <NUM>. The present device <NUM> according to Example <NUM> illustrated in <FIG> is different from the present device <NUM> according to Example <NUM> illustrated in <FIG> in that a first MCOK_A_4b and a second MCOK_B_5b are provided to form a series two-stage switch only in the V phase.

The second MCOK_B_5b is interposed between a connection point of the ACPT_21a and the current detector 11b. That is, the second MCOK_B_5b is connected such that the connection point of the ACPT_21a on the V phase side matches a connection point between the first MCOK A 4b and the second MCOK B 5b.

In the example, the volage detector 21b is disposed between the V phase and the W phase in the present device <NUM> according to Example <NUM> illustrated in <FIG>. In the present device <NUM>, the voltage detector 21b is connected such that a connection point of the voltage detector 21b on the V phase side matches the connection point between the first MCOK_A_4b and the second MCOK B 5b.

The present device <NUM> can block a ground fault circuit (that is, a ground fault current). In the present device <NUM>, for example, when the ACPT_21a has a ground fault on the side on which the ACPT_21a is connected to the V phase, the current detector 11b detects a ground fault current and inputs the ground fault current to the control device <NUM>.

When the ground fault current detected by the control device <NUM> is equal to or larger than a predetermined value, the control device <NUM> outputs a release instruction to the second MCOK_B_5b. Therefore, the second MCOK_B_5b is released to block the ground fault circuit (that is, the ground fault current).

Next, Example <NUM> of the present invention is described with reference to <FIG> is a configuration diagram of a present device <NUM> according to Example <NUM>. The present device <NUM> according to Example <NUM> illustrated in <FIG> is different from the present device <NUM> according to Example <NUM> in that second MCOKs_B_5a to 5c are interposed between the current detectors 11a to 11c and the AC motor <NUM> to form series two-stage switches in all three U, V, and W phases.

In a rail vehicle or the like provided with the present device <NUM> according to Example <NUM> illustrated in <FIG>, an effect of continuously operating the vehicle is reliably obtained by blocking the foregoing short circuit current. A description will be given while making comparison with the present devices <NUM> and <NUM> according to Example <NUM> illustrated in <FIG>, <FIG>, and <FIG>. In the present devices <NUM> and <NUM>, when the ACPT_21a has a short circuit failure, a short circuit current flows between the ACPT_21a and the AC motor <NUM> and is detected by the current detectors 11a and 11b and input to the control device <NUM>.

When the foregoing short circuit current can be blocked, the rail vehicle or the like provided with the present device <NUM> can be continuously operated. That is, since a plurality of circuits of the same type constitutes drive devices or the like for the rail vehicle, only a failed drive device is disconnected and the vehicle can be continuously operated using the other remaining drive device.

The control device <NUM> outputs a release instruction to the second MCOKs_B_5a to 5c. In the present device <NUM> illustrated in <FIG>, particularly, the second MCOKs_B_5a and 5b are released to have a high effect of blocking a short circuit current caused by a short circuit failure of the ACPT_21a.

In the present device <NUM> illustrated in <FIG>, the measures taken at the time of the failure of the ACPT_21a or the like can prevent the short circuit current caused by regenerative power by the ACPT_21a and the AC motor <NUM> (particularly, in the case in which the AC motor is the PMSM_2') from continuously flowing to generate a braking force in the AC motor <NUM>.

Since the two MCOKs are provided in each of the phases as illustrated in <FIG>, the first MCOKs_A_4 are turned on (closed) after turning on of the second MCOKs_B_5 provided on the AC motor <NUM> (PMSM_2') side at the time of the activation of the inverter device <NUM>.

More specifically, the second MCOKs_B_5 are turned on first, the ACPT_21a detects an inter-phase voltage (voltage between terminals) of the AC motor <NUM> to estimate the position and speed of a rotor of the motor.

After that, in a state in which the inverter device <NUM> is activated by the control device <NUM> based on information of the estimated position and the estimated speed, the first MCOKs_A are turned on. This can prevent an eddy current and an operation such as torque vibration and can start an operation as an inverter in a stable manner.

<FIG> is a configuration diagram of a present device <NUM> according to Example <NUM>, which corresponds to an embodiment of the invention. The present device <NUM> according tc Example <NUM> illustrated in <FIG> is different from the present device <NUM> according to Example <NUM> illustrated in <FIG> in the following features. That is, in the present device <NUM>, the current detectors 11a to 11c are provided on the AC motor <NUM>' side with respect to the second MCOKs_B_5a to 5c.

In addition, in the present device <NUM>, one (U phase side in <FIG>) of two phases connected to the ACPT_21a is connected between the first MCOK A 4a and the second MCOK B 5a. In addition, in the present device <NUM>, the other phase (V phase in <FIG>) is connected between the second MCOK B 5b and the current detector 11b.

The present device <NUM> having the foregoing configuration can start an operation as an inverter in a stable manner, like the present device <NUM> according to Example <NUM> illustrated in <FIG>, so that security is improved. That is, the present device <NUM> can prevent an eddy current and an operation such as torque vibration due to the order of turning on of the first MCOKs_A_4a to 4c and the second MCOKs B 5a to 5c.

As a result, the operation as the inverter can be started in a stable manner. In addition, since the current detectors 11a to 11c are disposed in the immediate vicinity of the AC motor <NUM> (<NUM>'), the present device <NUM> can detect a short circuit current caused by a short circuit failure on the AC motor side so that security is improved.

A defective state in which the permanent magnetic synchronous motor (PMSM_2') performs a regenerative operation at the time of a failure in each of a comparative device <NUM> illustrated in <FIG> and a comparative device <NUM> illustrated in <FIG> is described below. While the AC motor <NUM> of each of the present devices <NUM> to <NUM> illustrated in <FIG> is an induction motor or the PMSM_2', a motor of each of the comparative devices <NUM> and <NUM> illustrated in <FIG> and <FIG> is limited to the PMSM_2' and is indicated by a reference sign <NUM>' to distinguish them.

<FIG> is a configuration diagram of a three-phase AC motor drive device (comparative device <NUM>) according to Comparative Example <NUM>. In the comparative device <NUM> illustrated as Comparative Example <NUM> in <FIG>, current detectors 11a and 11b and MCOKs_A_4a to 4c are interposed in different phases on connection lines between an inverter device <NUM> and the PMSM_2'. In addition, in the comparative device <NUM>, an ACPT_21a is disposed between phases.

Regarding the order in which the devices are connected, in a region extending from the inverter device <NUM> to the PMSM_2', the current detectors 11a and 11b are interposed and are closer to the inverter device <NUM> than the MCOKs_A_4a to 4c are and farther from the PMSM_2' than the MCOKs_A_4a to 4c are. Therefore, in a state in which the MCOKs_A_4a to 4c are released, a regenerative current of the PMSM_2' cannot be measured.

The ACPT_21a is disposed closer to the PMSM_2' than the MCOKs_A_4a to 4c are. Therefore, in a state in which the MCOKs_A_4a to 4c are released, a regenerative voltage of the PMSM_2' can be measured. However, when the ACPT_21a has a short circuit failure, it is difficult to disconnect a portion of the failure only by performing an operation from a vehicle cab. As a result, a driver may need to give up continuously operating a rail vehicle with other normal power.

<FIG> is a configuration diagram of the comparative device <NUM>. <FIG> exemplifies that the comparative device <NUM> illustrated as Comparative Example <NUM> is used for a rail vehicle as a general direct-current electric vehicle. When the comparative device <NUM> is a direct-current electric vehicle, the comparative device <NUM> has a configuration in which one is connected to a direct-current train line and the other is connected to a portion that is a wheel or the like and contacts the ground. For the direct-current train line, a portion of the smoothing capacitor <NUM> on the direct-current power supply higher-level side is connected to a smoothing reactor <NUM> via a pantograph <NUM> that is a power collector.

In addition, a configuration for obtaining direct-current power by rectifying alternating-current power by an alternating-current overhead contact line or a configuration for obtaining direct-current power by a third rail method is known. Furthermore, a configuration for obtaining alternating-current power by noncontact power transmission and converting the alternating-current power to direct-current power by a rectifier or the like is used.

In the comparative device <NUM> illustrated in <FIG>, current detectors 11a and 11b and MCOKs_A_4a and 4c are interposed in different phases on connection lines between an inverter device <NUM> and the PMSM_2', and an ACPT_21a is disposed between phases.

The comparative device <NUM> illustrated in <FIG> and the comparative device <NUM> illustrated in <FIG> have a common configuration in which the current detectors 11a and 11b are disposed between the inverter device <NUM> and the MCOKs_A_4a and 4c or the ACPT_21a. Therefore, the comparative devices <NUM> and <NUM> have a feature in which the current detectors 11a and 11b cannot measure a regenerative current of the PMSM_2' in a state in which the MCOKs_A_4a to 4c are released.

On the other hand, the comparative device <NUM> illustrated in <FIG> and the comparative device <NUM> illustrated in <FIG> are different in the following feature. That is, the comparative device <NUM> has a circuit configuration in which only the one MCOK_A_4b among the three MCOKs_A_4a to 4c is interposed between the ACPT_21a and the PMSM_2'. In addition, the current detectors 11a and 11b are disposed closer to the inverter device <NUM> than the MCOK_A_4b is and farther from the PMSM_2' than the MCOK_A_4b is.

With the foregoing circuit configuration, the comparative device <NUM> illustrated in <FIG> cannot measure a regenerative voltage and a regenerative current of the PMSM_2' in a state in which the MCOKs_A_4a to 4c are released. However, when the ACPT_21a has a short circuit failure, it is possible to disconnect a portion of the failure only by performing an operation from the vehicle cab. As a result, it is possible to continuously operate the rail vehicle with other normal power.

The present devices <NUM> to <NUM> can be summarized as follows. The present devices <NUM> and <NUM> according to Example <NUM> illustrated in <FIG>, <FIG>, and <FIG> are representative examples.

Each of the current controllers is a combination of a current control element and a rectifying element. The current control element conducts or blocks a current flowing toward one direction. The rectifying element is connected to the current control element in parallel and conducts a current flowing toward a direction opposite to the one direction.

In each of the present devices <NUM> and <NUM>, the motor cutout contacts represented by the MCOKs_A_4 are connected between the inverter device <NUM> and the load and switch whether to electrically connect or disconnect the inverter device <NUM> to or from the load.

In addition, three-phase current power generated by the inverter device <NUM> for the U, V, and W phases is supplied to the load. On the other hand, the terminals of the current detector ACPT_21a having the pair of terminals are connected to at least two phases, for example, the U phase and the V phase. To detect a voltage between the U, V, and W phases, it is sufficient if the single ACPT_21a illustrated in <FIG> is provided or if the two ACPTs_21a and 21b illustrated in <FIG> are provided.

In addition, the current detectors <NUM> that detect three-phase currents to be supplied from the inverter device <NUM> to the load are connected to the U, V, and W phases, respectively. The circuit configuration from the inverter device <NUM> to the load is as follows. That is, the inverter device <NUM>, the load, the MCOKs_A_4, the current detectors <NUM>, and the ACPT_21a are connected such that the inverter device <NUM> is connected in the immediate vicinity of the MCOKs_A_4, then to the ACPT_21a , then to the current detectors <NUM>, and then to the load.

In each of the present devices <NUM> and <NUM> having the foregoing connection configuration, when the ACPT_21a has a short circuit failure (for example, a short circuit between the U and V phases illustrated in <FIG>), the MCOKs_A_4 are released. This release of the MCOKs_A_4 electrically disconnects the inverter device <NUM> from the AC motor <NUM>. Even in this state, the current detectors 11a and 11b can detect a short circuit current flowing in a path between the AC motor <NUM> and the ACPT_21a. This information can be given to the vehicle cab or the like. As a result, a driver or the like can easily take optimal security measures.

The case in which the MCOKs_A_4 are released corresponds to a case in which the load of the present device <NUM> or <NUM> is the PMSM_2', the present device <NUM> or <NUM> is used in, for example, a rail vehicle, a failure such as a short circuit failure of the ACPT_21a or a reduction in output of the inverter device <NUM> occurs. In such a case, a driver or the like may take optimal security measures to eliminate a regenerative braking action of the PMSM_2' and continuously operate the vehicle with other remaining power.

The following convenience is obtained by the configurations of the present devices <NUM> and <NUM>. That is, when the load at the initial design stage is an induction motor, and an MCOK is not required due to a low regenerative braking action, basic design may be made such that an MCOK required due to replacement of the induction motor used as the load with the PMSM_2' when it is not provided in the inverter device <NUM>, and the ACPT_21a are disposed in the immediate vicinity of the inverter device <NUM> in this order.

That is, to secure a space for the MCOKs and the ACPT_21a, the current detectors <NUM> are disposed in the immediate vicinity of the load while avoiding the space. In other words, even in the case in which the MCOKs and the ACPT_21s are not required in the inverter device <NUM> at the initial design stage, when the space is secured and the MCOKs and the ACPT_21a needs to be retrofitted, there is no trouble. That is, it is easy to secure the installation configuration of the inverter device <NUM> and compatibility of device arrangement, regardless of whether the MCOKs and the ACPT_21a are present.

[<NUM>] In each of the present devices <NUM> and <NUM> according to Example <NUM> illustrated in <FIG>, <FIG>, and <FIG>, the MCOKs_A_4 are preferably connected between connection points between the inverter device <NUM> and the ACPT_21a. The advantages of the MCOKs_A_4 being disposed in the immediately vicinity of the inverter device <NUM> are described above.

[<NUM>] A connection form of the circuits of the two phases to which the ACPT_21 is connected in the present device <NUM> according to Example <NUM> illustrated in <FIG> is as follows. In the circuit of one (for example, the U phase) of the two phases, the MCOK_A_4a is connected between the connection point of the ACPT_21a and the current detector 11a. In addition, in the circuit of the other phase (for example, the V phase), the MCOK_A_4b is connected between the inverter device <NUM> and the connection point of the ACPT_21a.

Regarding the detection of an inter-phase voltage, even when the ACPT_21 fails, a state in which the current detectors 11a to 11c can detect current values of the phases is maintained, and thus the control device <NUM> illustrated in <FIG> easily take corresponding security measures.

[<NUM>] In the present device <NUM> according to Example <NUM> illustrated in <FIG>, the MCOK_A_4b is connected as a first motor cutout contact in the V phase between the inverter device <NUM> and the connection point of the ACPT_21a. In the V phase, the MCOK_B_5b is connected as a second motor cutout contact between the connection point of the ACPT_21a and the current detector 11b.

According to the control device <NUM> illustrated in <FIG>, for example, even when a V-phase ground fault accident occurs due to a ground fault of the ACPT_21a, a state in which the current detector 11b can detect a V-phase ground fault current is maintained, and thus it is possible to easily take corresponding security measures.

[<NUM>] The present device <NUM> according to Example <NUM> illustrated in <FIG> includes the MCOKs_B_5 as second motor cutout contacts between the current detectors <NUM> and the load. According to this, the MCOKs_B_5 as the second motor cutout contacts form series two-stage switches with the MCOKs_A_4 as the first motor cutout contacts.

Even when a regenerative braking state occurs in, for example, a vehicle having the PMSM_2' due to a short circuit failure of the ACPT_21a, the control device <NUM> illustrated in <FIG> maintains a state in which the current detectors 11a and 11b can detect a regenerative current. In this case, when the control device <NUM> releases the MCOKs_B_5, it is easy to take corresponding security measures.

In addition, when only the second MCOKs_B_5 provided on the PMSM_2' side are turned on (closed) at the time of the activation of the inverter device <NUM> and the ACPT_21a detects an inter-phase voltage (voltage between terminals) of the PMSM_2, the position and speed of the rotor of the motor are estimated. After that, the first MCOKs_A are turned on based on information of the estimated position and the estimated speed in a state in which the inverter device <NUM> is activated by the control device <NUM>. This can prevent an eddy current and an operation such as torque vibration and start an operation as an inverter in a stable manner.

[<NUM>] The present device <NUM> according to Example <NUM> illustrated in <FIG> includes the series two-stage switches constituted by the first MCOKs_A_4 and the second MCOKs_B_5 between the inverter device <NUM> and the current detectors 11a to 11c. In addition, the circuit of the U phase of the two phases connected to the current detector ACPT_21a is connected between the first MCOK_A_4a and the second MCOK_B_5a. Furthermore, the circuit of the other V phase is connected between the second MCOK_B_5b and the current detector 11b.

The present device <NUM> having the foregoing configuration can start the operation as the inverter at a higher level in a stable manner so that security is improved. That is, the present device <NUM> can prevent an eddy current and an operation such as torque vibration due to the order of turning on of the first MCOKs_A_4a to 4c and the second MCOKs_B_5a to 5c. In addition, since the current detectors 11a to 11c are disposed in the immediate vicinity of the AC motor <NUM> in the present device <NUM>, the present device <NUM> can detect a short circuit current caused by a short circuit failure on the AC motor side so that security is improved.

Claim 1:
A three-phase AC motor drive device that drives a load (<NUM>), comprising:
an inverter device (<NUM>) that includes a plurality of current controllers each having a combination of a current control element configured to conduct or block a current flowing toward one direction and a rectifying element connected to the current control element in parallel and configured to conduct a current flowing toward a direction opposite to the one direction, and is configured to convert direct-current power supplied from a power supply into three-phase alternating-current power and drive the load (<NUM>);
a motor cutout contact (MCOK_A, MCOK_B) configured to electrically connect or disconnect the inverter device (<NUM>) to or from the load (<NUM>);
a voltage detector (ACPT) configured to detect a voltage between three phases and having terminals connected to circuits of at least two of the phases;
a current detector (<NUM>) configured to detect phase currents of the three phases; and
a control device (<NUM>) configured to acquire detection output of the voltage detector (ACPT) and control a switching operation of each current control element of the inverter device (<NUM>) based on the detection output such that an AC motor outputs desired torque, wherein
in a connection from the inverter device (<NUM>) to the load (<NUM>), the inverter device (<NUM>), the motor cutout contact (MCOK_A, MCOK_B), the voltage detector (ACPT), the current detector (<NUM>), and the load (<NUM>) are arranged in this order; characterized in that
in a circuit of one of the two phases connected to the voltage detector (ACPT), the motor cutout contact (MCOK_A, MCOK_B) is connected to a connection point of the voltage detector (ACPT) and the current detector (<NUM>),
in a circuit of the other phase, the motor cutout contact (MCOK_A, MCOK_B) is connected to the inverter device (<NUM>) and a connection point of the voltage detector (ACPT); and
in a phase in which a first motor cutout contact (MCOK_A) is disposed between the inverter device (<NUM>) and a connection point of the voltage detector (ACPT), a second motor cutout contact (MCOK_B) is connected to the connection point of the voltage detector (ACPT) and the current detector (<NUM>).