US-20260128703-A1 - RAILROAD-CAR POWER CONVERSION APPARATUS

US20260128703A1US 20260128703 A1US20260128703 A1US 20260128703A1US-20260128703-A1

Abstract

A power conversion apparatus includes: a three-phase inverter converting direct-current power into alternating-current power for a propulsion motor; and a magnetic core. The magnetic core includes: first and second cores penetrated by both a three-phase alternating-current power line and a common mode current circulation line; and a third core penetrated only by the three-phase alternating-current power line. The first core is disposed on a side closer to the three-phase inverter, the second core is disposed on a side closer to the propulsion motor, and the third core is disposed between the first core and the second core. In the first, second, and third cores, when at least one of three electric wires in the three-phase alternating-current power line is drawn out of the second core toward the propulsion motor, the at least one of the three electric wires is not in parallel with remaining one or two electric wires.

Inventors

Ryosuke NAKAGAWA
Yasuhiro Shiraki

Assignees

MITSUBISHI ELECTRIC CORPORATION

Dates

Publication Date: 20260507
Application Date: 20221116

Claims (10)

1 . A railroad-car power conversion apparatus for driving a propulsion motor installed on a railroad car, the railroad-car power conversion apparatus comprising: a three-phase inverter to convert direct-current power into alternating-current power for the propulsion motor; and a magnetic core penetrated by a three-phase alternating-current power line and a common mode current circulation line, the three-phase alternating-current power line being an electric wire that connects the three-phase inverter and the propulsion motor, the common mode current circulation line being an electric wire that connects a ground potential of the power conversion apparatus and a ground potential of the propulsion motor, wherein the magnetic core includes: a first core disposed on a side closer to the three-phase inverter, the first core being penetrated by both the three-phase alternating-current power line and the common mode current circulation line; a second core disposed on a side closer to the propulsion motor, the second core being penetrated by both the three-phase alternating-current power line and the common mode current circulation line; and a third core disposed between the first core and the second core, the third core being penetrated only by the three-phase alternating-current power line, and assuming that, in each of the first core, the second core, and the third core, a first surface is defined as a surface facing toward the three-phase inverter, and a second surface is defined as a surface facing toward the propulsion motor, when at least one of three electric wires included in the three-phase alternating-current power line is drawn out of the second core toward the second surface, the at least one of the three electric wires is not in parallel with remaining one or two electric wires.
2 . The railroad-car power conversion apparatus according to claim 1 , wherein the first core, the second core, and the third core are each formed in a rectangular annular shape or a circular annular shape, and a non-magnetic metal plate is installed on the second surface of the second core.
3 . The railroad-car power conversion apparatus according to claim 1 , wherein a non-magnetic metal plate is installed on the first surface of the first core.
4 . The railroad-car power conversion apparatus according to claim 3 , wherein when at least one of the three electric wires included in the three-phase alternating-current power line is drawn out of the first core toward the first surface, the at least one of the three electric wires is not in parallel with remaining one or two electric wires.
5 . The railroad-car power conversion apparatus according to claim 2 , comprising: a fourth core disposed between the first core and the third core, the fourth core being penetrated only by the three-phase alternating-current power line; and a fifth core disposed between the second core and the third core, the fifth core being penetrated only by the three-phase alternating-current power line, wherein the fourth core and the fifth core are each formed in a rectangular annular shape or a circular annular shape, and assuming that, in each of the fourth core and the fifth core, a third surface is defined as a surface facing toward the three-phase inverter, and a fourth surface is defined as a surface facing toward the propulsion motor, a non-magnetic metal plate is installed on each of the fourth surface of the first core, the third surface of the fourth core, the fourth surface of the fifth core, and the third surface of the second core.
6 . The railroad-car power conversion apparatus according to claim 2 , wherein the non-magnetic metal plate is formed such that the non-magnetic metal plate has a thickness equal to or greater than a skin depth.
7 . The railroad-car power conversion apparatus according to claim 1 , wherein the common mode current circulation line is divided into two portions penetrating the first core and the second core.
8 . The railroad-car power conversion apparatus according to claim 7 , wherein one of the two portions into which the common mode current circulation line has been divided is disposed in parallel with a first electric wire, the first electric wire being one of the three electric wires included in the three-phase alternating-current power line, and another of the two portions into which the common mode current circulation line has been divided is disposed in parallel with a second electric wire, the second electric wire being one of the three electric wires included in the three-phase alternating-current power line, the one of the three electric wires being different from the first electric wire.
9 . The railroad-car power conversion apparatus according to claim 3 , comprising: a fourth core disposed between the first core and the third core, the fourth core being penetrated only by the three-phase alternating-current power line; and a fifth core disposed between the second core and the third core, the fifth core being penetrated only by the three-phase alternating-current power line, wherein the fourth core and the fifth core are each formed in a rectangular annular shape or a circular annular shape, and assuming that, in each of the fourth core and the fifth core, a third surface is defined as a surface facing toward the three-phase inverter, and a fourth surface is defined as a surface facing toward the propulsion motor, a non-magnetic metal plate is installed on each of the fourth surface of the first core, the third surface of the fourth core, the fourth surface of the fifth core, and the third surface of the second core.
10 . The railroad-car power conversion apparatus according to claim 3 , wherein the non-magnetic metal plate is formed such that the non-magnetic metal plate has a thickness equal to or greater than a skin depth.

Description

FIELD The present disclosure relates to a railroad-car power conversion apparatus for driving a propulsion motor installed on a railroad car. BACKGROUND A power conversion apparatus includes a switching element such as an insulated gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect-transistor (MOSFET). In power conversion apparatuses of recent years, switching voltage and switching operation speed are increasing along with an increase in the withstand voltage and frequency of switching elements. In general, it is known that switching operation performed in a power conversion apparatus causes common mode current which is zero-phase current. It is also known that switching operation performed in a power conversion apparatus causes leakage current flowing to the ground via a parasitic capacitance located between the ground and an alternating-current power line connecting the power conversion apparatus and a load. In addition, it is also known that switching operation performed in a power conversion apparatus causes leakage current flowing to a peripheral device other than a load via a parasitic capacitance located between an alternating-current power line and a housing accommodating the power conversion apparatus. These leakage currents are distinguished from zero-phase currents, as common mode currents flowing through a grounding system. As described above, an increase in switching voltage and switching operation speed will increase zero-phase current and leakage current, and increase radiation noise and conduction noise. Thus, there is a problem in that the increase in switching voltage and switching operation speed adversely affect peripheral communication devices and the like. In order to reduce zero-phase current, in the conventional techniques, alternating-current power lines are wound around or passed through the same magnetic core. In addition, Patent Literature 1 below discloses a technique in which in order to reduce leakage current, a ground terminal of a power conversion apparatus and a ground terminal of a load are connected by an electric wire called a common mode current circulation line, and alternating-current power lines and the common mode current circulation line are wound around or passed through the same magnetic core. Citation List Patent Literature Patent Literature 1: Japanese Patent Application Laid-open No. 2001-086734 SUMMARY OF INVENTION Problem to Be Solved by the Invention When the technique of Patent Literature 1 is used, the impedance of a circulation loop of a ground circuit is larger than the impedance of a circulation loop of the common mode current circulation line. Therefore, leakage current flowing through the circulation loop of the ground circuit can be reduced. However, it is described that when the technique of Patent Literature 1 is used, a peak value of zero-phase current is larger than when only the alternating-current power lines are wound around or passed through the same magnetic core. As described above, zero-phase current causes radiation noise and conduction noise. In the case of a railroad-car power conversion apparatus, since an extremely large current flows through a propulsion motor serving as a load, an increase in zero-phase current cannot be tolerated. The present disclosure has been made in view of the above, and an object of the present disclosure is to obtain a railroad-car power conversion apparatus capable of reducing leakage current while preventing an increase in zero-phase current. Means to Solve the Problem In order to solve the above-described problem and achieve the object, a railroad-car power conversion apparatus according to the present disclosure is a railroad-car power conversion apparatus for driving a propulsion motor installed on a railroad car, the railroad-car power conversion apparatus including: a three-phase inverter that converts direct-current power into alternating-current power for the propulsion motor; and a magnetic core penetrated by a three-phase alternating-current power line and a common mode current circulation line. The three-phase alternating-current power line is an electric wire that connects the three-phase inverter and the propulsion motor. The common mode current circulation line is an electric wire that connects a ground potential of the power conversion apparatus and a ground potential of the propulsion motor. The magnetic core includes: first and second cores penetrated by both the three-phase alternating-current power line and the common mode current circulation line; and a third core penetrated only by the three-phase alternating-current power line. The first core is disposed on a side closer to the three-phase inverter, and the second core is disposed on a side closer to the propulsion motor. In addition, the third core is disposed between the first core and the second core. Assuming that, in each of the first core, the second core, and the third core, a first surface is defined as