Power conversion device

Abstract

Provided is a power conversion device (1) in which the breakage of components of an internal circuit such as an input circuit can be suppressed even in an abnormal state such as a ground fault. In the power conversion device (1), which takes AC voltage as an input and outputs DC voltage through voltage doubler rectification, an inrush current suppression unit (105) is disposed on the neutral line side of the AC current.

Description

Power Conversion Device

[0001] The present invention relates to a power conversion device that receives a single-phase AC voltage and outputs a DC voltage by voltage doubler rectification.

[0002] A motor drive power conversion device generally consists of a rectifier that converts AC voltage to DC voltage, a capacitor that smooths the DC voltage, and an inverter that inversely converts the DC voltage. The rectifier uses two main circuit types depending on the AC voltage value: a full-wave rectifier circuit when the AC voltage exceeds 200 volts, and a voltage-doubler rectifier circuit when the AC voltage is approximately 100 to 120 volts. A voltage-doubler rectifier circuit can generate a DC voltage that is approximately twice the peak value of the AC voltage. Therefore, whether the AC voltage is a 100-volt system or a 200-volt system, the inverter section can be configured using the same components as for a 200-volt system.

[0003] Patent Document 1 discloses a power conversion device that performs voltage doubler rectification on a single-phase AC power and outputs AC power using a two-phase inverter circuit.

[0004] Japanese Patent Application Publication No. 10-210789

[0005] FIG. 14 of Patent Document 1 shows a circuit configured with an input terminal for inputting an AC voltage, a noise filter circuit consisting of a fuse, an inductance element, and a capacitor, an inrush current suppression circuit consisting of a resistor, a switch element, and a delay circuit for suppressing charging current when the power is turned on, and a voltage doubler rectifier circuit consisting of two diodes and two capacitors.

[0006] In this figure, one of the AC input lines is represented as L and the other as N. L and N in single-phase AC voltage generally represent the voltage line side and neutral line (ground) side in a single-phase three-wire commercial power supply. L is the voltage line side (live side) and N is the neutral line side (neutral side).

[0007] In the figure, if a ground fault occurs on the high-voltage side of the DC voltage or the low-voltage side of the DC voltage on the right side of the figure due to incorrect wiring or dust adhesion, the ground fault current will flow into the inrush current suppression circuit, because the inrush current suppression circuit is connected in series with the voltage line side of the AC input line on the left side of the figure.

[0008] In the figure, the inrush current suppression circuit is configured so that the switch element turns on after a delay time determined by the delay circuit. Therefore, if the AC input line is turned on while the DC voltage is grounded, the ground-fault current flows through resistor R5, a component of the inrush current suppression circuit. As a result, resistor R5 may burn out or be destroyed before the ground-fault current is limited by resistor R5 and the protective fuse blows.

[0009] One of the purposes of providing a fuse is to prevent damage to internal circuit components in the event of an abnormal condition such as a ground fault, but in the circuit shown in the figure, there is a possibility that the fuse will not achieve this purpose.

[0010] Therefore, an object of the present invention is to provide a power conversion device that outputs a DC voltage by voltage doubler rectification, which can suppress damage to components in internal circuits such as an input circuit even in an abnormal state such as a ground fault.

[0011] One example of a means for solving the above problem is to arrange an inrush current suppression unit on the neutral line side of the AC current in a power conversion device that inputs an AC voltage and outputs a DC voltage by voltage doubler rectification.

[0012] In the power conversion device according to the present invention, which outputs a DC voltage by voltage rectification, damage to components in the internal circuit due to fuse blowing can be prevented in the event of an abnormal condition such as a DC voltage ground fault.

[0013] FIG. 1 is a circuit configuration diagram of a power conversion device according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of an embodiment of the present invention. FIG. 3 is an explanatory diagram of an embodiment of the present invention. FIG. 4 is an explanatory diagram of an embodiment of the present invention. FIG. 5 is an explanatory diagram of a comparative example. FIG. 6 is an explanatory diagram of a comparative example. FIG. 7 is an explanatory diagram of an example of a path of a ground fault current. FIG. 8 is an explanatory diagram of an example of a path of a ground fault current. FIG. 9 is an explanatory diagram of an example of a nameplate.

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] 1 is a circuit diagram of a power conversion device 1 according to this embodiment. The power conversion device 1 includes a rectifier 101 that receives an AC voltage 2 and outputs a DC voltage, a capacitor 102 that smooths the DC voltage, a regenerative braking unit 103 that is connected in parallel with the capacitor 102, an inverter 104 that converts the DC voltage into AC power, an inrush current suppression unit 105, and a main circuit terminal block 108. Also shown are a braking resistor 33, a regenerative braking unit 106, and a fuse unit 107 as examples of external equipment that can be connected to the power conversion device 1.

[0016] The connection of rectifier 101 and capacitor 102 shown in Figure 1 is generally called a voltage doubler rectifier circuit. Diode 11 and capacitor 21 are conductive during the positive half cycle of AC voltage 2 (when L1 has a higher voltage than N), and diode 12 and capacitor 22 are conductive during the negative half cycle of AC voltage 2 (when L1 has a lower voltage than N). Capacitors 21 and 22 each half-wave rectify AC voltage 2. For example, if the effective value of the AC voltage is 100 volts, the voltages of capacitors 21 and 22 will each be approximately 141 volts, which is the peak voltage of the AC voltage, and the DC voltage will be approximately 282 volts, which is the sum of the voltages of capacitors 21 and 22.

[0017] The regenerative braking unit 103 is composed of a diode 31 and a switching element 32. A braking resistor 33 is connected between the connection point of the diode 31 and the switching element 32 and the high-voltage side of the DC voltage. In the figure, RB in 103 is connected to RB on the left side of the figure. When the DC voltage exceeds a predetermined value, the regenerative braking unit 103 drives the switching element 32, causing the braking resistor 33 to consume energy and suppressing the rise in the DC voltage.

[0018] The inverter unit 104 is made up of switching elements 41 to 46, and outputs AC power to the motor 3. Note that U, V, and W on the right side of the figure are connected to U, V, and W on the left side of the figure, respectively. Although the circuit symbol for an IGBT is used as a representative example for the switching elements in Figure 1, other power semiconductors such as a MOSFET can also be used.

[0019] The inrush current suppression unit 105 is composed of a current-limiting resistor 51 and a relay 52, and is arranged to limit the charging current to the capacitors 21 and 22 when the AC voltage 2 is applied. When the potential difference between the high-voltage side and the low-voltage side of the DC voltage is lower than a predetermined value, such as immediately after the AC voltage 2 is applied, the relay 52 is in an OFF state, and the capacitors 21 and 22 are charged via the current-limiting resistor 51. When the capacitors 21 and 22 are charged and exceed a predetermined value, the relay 52 transitions to an ON state. Note that while a relay is used as a representative in FIG. 1, other elements such as a triac may also be used. Also, although a current-limiting resistor is used in FIG. 1, an element having a resistance component such as a thermistor may also be used.

[0020] The regenerative braking unit 106 is installed externally to the power conversion device 1 in parallel with the DC voltage for the purpose of further increasing the braking torque of the inverter relative to the regenerative braking section 103. The fuse unit 107 is provided to prevent secondary damage to devices other than the power conversion device 1 sharing the AC voltage 2 and to prevent damage to components inside the power conversion device 1 in the event of an unexpected event such as a ground fault in the circuit within the power conversion device 1. Therefore, in the event of an unexpected event such as a ground fault due to incorrect wiring, the desired operation is for the fuse in the fuse unit 107 to blow without damaging the components inside the power conversion device 1. Note that, although fuses 71 and 72 are shown in FIG. 1 as being installed on both input lines of the fuse unit 107, they may be connected only to one of the voltage lines. Alternatively, a device such as a breaker, which has the function of cutting off current when a certain amount of current flows, may be used instead of a fuse.

[0021] The main circuit terminal block 108 is a terminal block for connecting the inside of the power conversion device 1 with peripheral equipment external to the power conversion device 1. As described above, the power conversion device 1 is provided with terminals that can be wired so that it can be connected to various external equipment such as the braking resistor 33, the regenerative braking unit 106, and the motor 3. Hereinafter, the names of the high-voltage parts and the like connected to the main circuit terminal block 108 used in the present invention will be described.

[0022] The AC voltage 2 is a single-phase AC voltage with one voltage line and the other neutral line of a single-phase three-wire system, and the voltage line side is denoted as L1 and the neutral line side as N. The high voltage side of the DC voltage is denoted as +, the low voltage side as -, the terminal to which the braking resistor 33 is connected is denoted as RB, and the three-phase AC output to the motor 3 is denoted as U, V, and W, respectively.

[0023] Next, referring to FIG. 2, the operation of the power conversion device 1 described in this embodiment when a ground fault occurs on the high voltage side (+) of the DC voltage due to a wiring error by an operator or the adhesion of dust will be described.

[0024] 2A and 2B show the operation when the power is turned on in a state where the high voltage side (+) of the DC voltage has a ground fault and is at the same potential as the neutral line of the AC voltage 2, in comparison with the circuit configuration diagram of Fig. 1, and show the main components related to circuit protection extracted from the circuit configuration diagram of Fig. 1. Figs. 2A and 2B focus on the operation between the AC voltage 2 and the DC voltage, and do not show the regenerative braking unit 103, inverter unit 104, etc. of Fig. 1. Figs. 2A and 2B are also diagrams for explaining the operation immediately after power is turned on, and relay 52 of Fig. 1 is not shown because it is assumed to be always in the off state.

[0025] Note that Figure 2A shows a positive half cycle of the AC voltage 2 (when the voltage of L1 is higher than that of N), and Figure 2B shows a negative half cycle of the AC voltage 2 (when the voltage of L1 is lower than that of N). The dashed line indicates the current path, and the dashed-dotted line connecting the high-voltage side (+) of the DC voltage and the neutral wire (N) indicates the path of the ground fault.

[0026] 2A , if AC voltage 2 is applied during a positive half cycle of AC voltage 2 while the high-voltage side (+) of the DC voltage is grounded, a ground-fault current flows through the route of AC voltage 2, fuse 71, and diode 11. This current is a current in which the voltage of AC voltage 2 is short-circuited via system impedance or the like, and therefore a large current sufficient to blow fuse 71 flows. By making diode 11 on the short-circuit path an element that can withstand the current that would blow fuse 71, the operation of blowing the external fuse without damaging the components inside power conversion device 1, which is the object of the present invention, can be achieved.

[0027] As shown in Figure 2B, during the negative half-cycle of AC voltage 2, if AC voltage 2 is applied while the high-voltage side (+) of the DC voltage is grounded, current flows through the route AC voltage 2 - fuse 72 - current-limiting resistor 51 - capacitor 22 - diode 12 - fuse 71. The illustrated current is the initial charging operation of capacitor 22 and is normal operation because it flows regardless of whether a ground fault exists. The voltage of current-limiting resistor 51 is applied to capacitor 21 in the direction opposite to the polarity of capacitor 21. While this is not a problem if a non-polar capacitor such as a film capacitor is used for capacitor 21, if a polar capacitor such as an electrolytic capacitor is used, a voltage in the reverse direction will be momentarily applied. However, the period during which this voltage is applied is short, consisting of only the time constant determined by the resistance value of current-limiting resistor 51 and the capacitance of capacitor 22 during initial charging. Furthermore, as capacitor 22 charges, the current transiently decreases, and the voltage also decays. Therefore, even when a polarized capacitor is used for the capacitor 21, the specifications can be set so that the capacitor has characteristics that can withstand the negative half-cycle period of the AC voltage 2. Therefore, the specifications can be set so as to prevent damage to the components inside the power conversion device 1 during the negative half-cycle period of the AC voltage 2.

[0028] After the period shown in Fig. 2B, AC voltage 2 operates in the positive half cycle shown in Fig. 2A. Therefore, even if the high voltage side (+) of the DC voltage has a ground fault, power conversion device 1 shown in Fig. 1 can realize an operation in which the components inside power conversion device 1 are not damaged and the external fuse is blown.

[0029] In other words, arranging the current-limiting resistor 51 in series on the neutral line side of the AC voltage is one example of a feature of the present invention. Meanwhile, Patent Document 1 only discloses an example in which the inrush current suppression circuit 70 is arranged on the voltage line side of the AC voltage as shown in FIG. 14 . Because the installation sides of the current-limiting resistors are opposite in Patent Document 1 and the present invention, this fundamental difference allows the present invention to achieve unique effects that cannot be achieved in Patent Document 1. That is, in a power conversion device that outputs DC voltage by voltage doubler rectification, damage to internal circuit components due to fuse blowout can be prevented in the event of an abnormal state such as a DC voltage ground fault.

[0030] In the above description of this embodiment, the example of a current-limiting resistor has been used, but similarly, all examples in which an inrush current suppression circuit or an element that can contribute to suppressing inrush current is arranged in series on the neutral line side of the AC voltage are included in the scope of disclosure of this specification.

[0031] Next, with reference to FIG. 3, the operation of the power conversion device 1 when a ground fault occurs on the low voltage side (-) of the DC voltage due to a wiring error by an operator or the adhesion of dust, etc. will be described.

[0032] Figures 3A and 3B show the operation when the power is turned on in a state where the low voltage side (-) of the DC voltage has a ground fault and is at the same potential as the neutral wire of the AC voltage 2, as compared to the circuit configuration diagram of Figure 1. As with Figure 2, the main components related to circuit protection have been extracted from the circuit configuration diagram of Figure 1. Also, as with Figure 2A, Figure 3A shows the positive half cycle of the AC voltage 2, and as with Figure 2B, Figure 3B shows the negative half cycle of the AC voltage 2. The dashed line indicates the current path, and the dashed-dotted line connecting the low voltage side (-) of the DC voltage and the neutral wire (N) indicates the ground fault path.

[0033] As shown in Figure 3A, if AC voltage 2 is applied during a positive half cycle of AC voltage 2 while the low-voltage side (-) of the DC voltage has a ground fault, current flows through the route AC voltage 2, fuse 71, diode 11, capacitor 21, current-limiting resistor 51, and fuse 72. The current shown is the initial charging operation of capacitor 21, and is normal operation because it flows regardless of whether a ground fault exists. Also, unlike Figure 2B, the voltage of current-limiting resistor 51 is applied to capacitor 22 in the same direction as the polarity of capacitor 21, so no damage occurs to components inside power conversion device 1 during the positive half cycle of AC voltage 2.

[0034] 3B, if AC voltage 2 is applied during the negative half cycle of AC voltage 2 while the low-voltage side (-) of the DC voltage is grounded, a ground-fault current flows through the route of AC voltage 2, diode 12, and fuse 71. This current is a current in which the voltage of AC voltage 2 is short-circuited via system impedance or the like, and therefore a large current sufficient to blow fuse 71 flows. By making diode 12 on the short-circuit path an element that can withstand the current that would blow fuse 71, the operation of blowing the external fuse without damaging the components inside power conversion device 1, which is the object of the present invention, can be achieved.

[0035] After the period shown in Fig. 3A, AC voltage 2 operates in a negative half cycle as shown in Fig. 3B. Therefore, even if the low-voltage side (-) of the DC voltage in power conversion device 1 shown in Fig. 1 is faulted to ground, the components inside power conversion device 1 are not damaged and the external fuse blows.

[0036] As described above with reference to FIGS. 2 and 3, the present invention can prevent damage to components in the internal circuit due to the blowing of a fuse when a ground fault occurs on either the high-voltage side or the low-voltage side of the DC voltage.

[0037] Next, a comparative example of the present invention will be described with reference to Figures 4A and 4B. Figures 4A and 4B are diagrams illustrating the concept of circuit protection extracted from Figure 14 of Patent Document 1, similar to Figures 2A and 3A of the present invention.

[0038] Note that Figure 4A shows a positive half cycle of AC voltage 2, and Figure 4B shows a negative half cycle of AC voltage 2, with the dashed lines indicating the current path and the dashed-dotted line connecting the high voltage side (+) of the DC voltage and the neutral wire (N) indicating the path of the ground fault.

[0039] As shown in Fig. 4A, if AC voltage 2 is applied during a positive half cycle of AC voltage 2 while the high-voltage side (+) of the DC voltage has a ground fault, a ground-fault current flows through the route of AC voltage 2-fuse 71-current-limiting resistor 51-diode 11. This current is a current in which the voltage of AC voltage 2 is short-circuited via the system impedance and the resistance value of current-limiting resistor 51. Unlike Fig. 2A, because current-limiting resistor 51 is present in the path of the ground-fault current, the ground-fault current is limited by the resistance value of current-limiting resistor 51.

[0040] 4B, during the negative half cycle of AC voltage 2, if AC voltage 2 is applied while the high-voltage side (+) of the DC voltage is faulted to ground, current flows through the route AC voltage 2-fuse 72-current-limiting resistor 51-capacitor 22-diode 12-fuse 71. The current shown is the initial charging operation of capacitor 22, and is normal operation because it flows regardless of whether a ground fault exists.

[0041] 4B, consider a state in which capacitor 22 is not charged at all, the voltage of capacitor 22 is approximately 0 volts, and the AC voltage of AC voltage 2 momentarily reaches a peak. In this case, because the voltage of capacitor 22 is approximately 0 volts, a current flows as an inrush current when AC voltage 2 is momentarily short-circuited via the system impedance and the resistance value of current-limiting resistor 51. In other words, a current of the same magnitude as the current shown in FIG. 4A may momentarily flow. Therefore, if fuse 71 were designed to blow in the event of an abnormality as shown in FIG. 4A, there is a possibility that fuse 71 will blow even during the initial charging operation, which is normally a normal operation.

[0042] Furthermore, although not shown, in the input circuit described in Patent Document 1, when a ground fault occurs on the low voltage side (-) of the DC voltage and the power is turned on in a state where the low voltage side (-) is at the same potential as the neutral line of the AC voltage 2, the operation is in a state where the polarity is reversed from the operation shown in FIG. 4, and the same problem occurs.

[0043] For this reason, to reiterate, the installation side of the current-limiting resistor is the exact opposite between Patent Document 1 and the present invention, and with this fundamental difference as a background, the present invention can achieve unique effects that cannot be achieved in Patent Document 1.

[0044] As described above, the novelty and inventive step of the present invention are already clear compared to the disclosure of Fig. 14 of Patent Document 1. Here, we will provide a supplementary explanation below that the present invention is effective even when the timing of the ground fault differs from the explanation of Figs. 2 and 3.

[0045] 5A and 5B are diagrams for explaining the operation when a ground fault occurs on the high voltage side (+) of the DC voltage or the low voltage side (-) of the DC voltage after the power supply is turned on with normal wiring that is not in a ground fault state, the relay 52 transitions to the on state, and the power conversion device 1 starts up.

[0046] If a ground fault occurs during the positive half cycle of AC voltage 2 shown in Fig. 5A, the ground fault current does not flow through relay 52, and therefore the operation is the same as in Fig. 2A described above, causing fuse 71 to blow, regardless of whether relay 52 is present. Also, if a ground fault occurs during the negative half cycle of AC voltage 2 shown in Fig. 5B, in addition to the normal voltage doubler rectification operation shown by the dashed line in Fig. 5B, a short-circuit current in capacitor 21 flows through the route passing through capacitor 21, fuse 72, and relay 52 in Fig. 5B (the route shown by the two-dot dashed line in Fig. 5B).

[0047] Here, if the fuse 72 is designed to blow due to a short-circuit current of the capacitor 21, the relay 52 can be designed to withstand the short-circuit current of the capacitor 21, thereby realizing an operation in which the external fuse blows without damaging the components inside the power conversion device 1. Furthermore, if the fuse 72 is designed not to blow due to the short-circuit current of the capacitor 21, the short circuit of the capacitor 21 will roughly halve the potential difference between the high-voltage side (+) of the DC voltage and the low-voltage side (-) of the DC voltage compared to normal voltage-doubler rectification operation. Therefore, the relay 52 transitions to the OFF state, and after the operation shown in FIG. 2B described above, the operation transitions to the operation shown in FIG. 2A described above. As a result, as described above, an operation in which the external fuse blows without damaging the components inside the power conversion device 1 is realized.

[0048] As described above, in the present invention, in a power conversion device 1 that inputs a single-phase AC voltage generated between the voltage line side (L1) and the neutral line side (N), performs voltage doubler rectification via a fuse unit 107 and an inrush current suppression unit 105, and outputs a DC voltage, one side of the inrush current suppression unit 105 is connected to the neutral line side (N), and the other side is connected to the connection point of the capacitors 21 and 22. This makes it possible to achieve a unique effect that cannot be achieved in FIG. 14 of Patent Document 1. That is, in a power conversion device that outputs a DC voltage by voltage doubler rectification, damage to components in the internal circuit due to fuse melting can be prevented in the event of an abnormal state such as a DC voltage ground fault.

[0049] The present invention, described above in detail, can be summarized as a power conversion device that inputs AC voltage and outputs DC voltage through voltage doubler rectification, characterized in that an inrush current suppression unit is arranged on the neutral line side of the AC current. Furthermore, a power plant characterized by having a motor using this power conversion device can reduce the possibility of failure and achieve a more stable operating rate. Furthermore, by using the above-mentioned power plant as at least a part of a production facility, the possibility of failure can be reduced, and a highly reliable production facility capable of more stable production can be constructed.

[0050] Next, this embodiment will be described with reference to Fig. 6. In the power conversion device 1 described in this embodiment, diodes 13 and 14 are added in parallel to the diodes 11 and 12 that are components of the rectifier 101 in Fig. 1 to form the rectifier 101.

[0051] Similar to FIG. 2A , FIG. 6 illustrates the operation when power is applied in a state where the high-voltage side (+) of the DC voltage has a ground fault and is at the same potential as the neutral line of the AC voltage 2. Similarly to FIG. 2 , major components related to circuit protection are extracted. Similar to FIG. 2A of Example 1, when AC voltage 2 is applied in a state where the high-voltage side (+) of the DC voltage has a ground fault, a ground-fault current flows through the AC voltage 2, fuse 71, and rectifier unit 101. Here, since the ground-fault current flows through the diodes of the rectifier unit 101 during the period from when power is applied until the fuse 71 melts, it is desirable that the diodes of the rectifier unit 101 have a configuration that allows them to withstand instantaneous currents, such as surge forward currents, to melt the fuse 71. Therefore, as shown in FIG. 6 , by increasing the number of diodes connected in parallel in the rectifier unit 101, the instantaneous current can be shared by the number of diodes connected in parallel, and damage to the rectifier unit 101 can be more effectively prevented than when diodes are not connected in parallel.

[0052] Of course, a parallel arrangement of three or more is also within the scope of the disclosure of this specification.

[0053] Next, this embodiment will be described with reference to Fig. 7. Fig. 7 is an explanatory diagram of a terminal block nameplate 109 that clearly indicates the terminal arrangement that can be used in the power conversion device 1.

[0054] As mentioned above, the power conversion device 1 is connected to peripheral equipment such as the fuse unit 107, braking resistor 33, regenerative braking unit 106, and motor 3, for example. As shown in FIG. 7 , a terminal block nameplate 109 is added that clearly indicates the names of signals connected to the main circuit terminal block, such as the voltage line (L1) and ground line (N), to prevent incorrect wiring, which is one cause of ground faults. This reduces the risk of abnormal conditions, such as DC voltage ground faults caused by human error, and prevents damage to internal circuit components due to fuse blowouts. Of course, the risk of ground faults is not limited to human error; it can also be caused by a variety of external high voltages, such as dust and lightning, so the necessity and effectiveness of the present invention are important regardless of whether a nameplate is provided.

[0055] 1: Power conversion device 2: AC voltage 3: Motor 11, 12, 13, 14, 31: Diode 21, 22, 102: Capacitor 32, 41, 42, 43, 44, 45, 46: Switching element 33: Braking resistor 51: Current-limiting resistor 52: Relay 71, 72: Fuse 101: Rectifier section 103: Regenerative braking section 104: Inverter section 105: Inrush current suppression section 106: Regenerative braking unit 107: Fuse unit 108: Main circuit terminal block 109: Terminal block nameplate

Claims

1. A power conversion device that inputs AC voltage and outputs DC voltage through voltage doubler rectification, in which an inrush current suppression unit is placed on the neutral line side of the AC current.

2. A power plant having a motor driven by the power conversion device according to claim 1.

3. A production facility having the power unit according to claim 2.

4. A power conversion device that inputs an AC voltage and outputs a DC voltage, comprising: a first input terminal to which the voltage line side of the AC voltage is connected; a second input terminal to which the neutral line side is connected; a rectifier unit connected to the first input terminal for voltage-doubled rectification of the AC voltage and outputting a DC voltage; a first capacitor arranged on the high-voltage side of the DC voltage; a second capacitor arranged on the low-voltage side of the DC voltage; and an inrush current suppression unit for suppressing inrush current to the capacitors, the inrush current suppression unit being connected to the second input terminal.

5. A power conversion device as claimed in claim 4, wherein the first capacitor and the second capacitor are connected in series between the high voltage side of the DC voltage and the low voltage side of the DC voltage, and the inrush current suppression unit is connected at one end to the second input terminal and at the other end to the connection point between the first capacitor and the second capacitor.

6. A power conversion device as claimed in claim 4, wherein the rectification section is composed of a first diode having a cathode connected to the high voltage side of the DC voltage and an anode connected to the first input terminal, and a second diode having a cathode connected to the first input terminal and an anode connected to the low voltage side of the DC voltage.

7. A power conversion device according to claim 4, wherein the first capacitor is charged during a half cycle in which the voltage on the voltage line side of the AC voltage is higher than the neutral line side, and the second capacitor is charged during a half cycle in which the voltage on the voltage line side of the AC voltage is lower than the neutral line side.

8. The power conversion device according to claim 4, wherein an overcurrent protection device is connected in series between the first input terminal and a commercial power source.

9. The power conversion device according to claim 6, wherein a third diode and a fourth diode are connected in parallel to the first diode and the second diode, respectively.

10. A power conversion device according to claim 4, comprising: a main circuit terminal block connectable to the first input terminal, the second input terminal, the high voltage side of the DC voltage, or the low voltage side of the DC voltage; and a nameplate indicating the signal names of the main circuit terminal block.

11. A power conversion device according to claim 4, comprising: an inverter section for converting the DC voltage into an AC voltage; and a terminal for outputting the AC voltage.

12. The power conversion device according to claim 11, further comprising: a regenerative braking section connected in parallel to said capacitor; and a terminal of said regenerative braking section.

13. A power conversion device according to claim 4, wherein the inrush current suppression section includes a parallel body of a current limiting resistor and a relay.

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