JP4973125B2 - Inverter snubber capacitor and cooling structure of snubber circuit - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a pulse power source that uses a capacitor or the like as a DC power source to generate a high-voltage, large-current pulse, and in particular, a snubber capacitor for an inverter used in a capacitor charging device that charges a capacitor periodically to a set voltage And a snubber circuit cooling structure.

  FIG. 8 shows a circuit configuration of a conventional capacitor charging device, where 1 is a capacitor, and an inverter 3 is connected to the capacitor 1 via a stray inductance 2. The inverter circuit 3 is configured by bridge-connecting semiconductor switches S1 and S2 made of IGBT or the like, and converts DC power into AC power. The output of the inverter circuit 3 is composed of a diode bridge circuit via a step-up transformer 4 and connected to a rectifier circuit 5 for converting an AC voltage into a DC voltage. The output of the rectifier circuit 5 is connected to a capacitor 7 via a reactor 6. . This circuit operation will be described. First, a DC voltage is stored in the capacitor 1 using a three-phase power supply, a rectifier circuit, etc., and the stray inductance 2 from the capacitor 1 to the primary side of the step-up transformer 4 when the pair of semiconductor switches S1 are turned on. The current i1 flows through the path of the semiconductor switch S1, the step-up transformer 4 and the semiconductor switch S1, and the current i2 flows through the path of the rectifier circuit 5, the reactor 6, and the capacitor 7 to the secondary side of the step-up transformer 4. The capacitor 7 is charged while accumulating energy in 6. Next, when the semiconductor switch S1 is turned off, the current i3 flows through the path of the reactor 6, the capacitor 7, and the rectifier circuit 5, the energy stored in the reactor 6 is transferred to the capacitor 7, and the capacitor 7 is further charged. However, at the moment when the semiconductor switch S1 of the inverter circuit 3 is turned off, an overvoltage is generated in the semiconductor switch S1 due to the influence of the current i1 and the stray inductance 2. Therefore, a snubber capacitor 8 is connected in parallel with the inverter circuit 3 in order to prevent the semiconductor switch S1 from being damaged by this overvoltage. FIGS. 9A and 9B show the charging current and charging voltage of the capacitor 7.

  FIG. 10 shows a circuit configuration of another conventional capacitor charging apparatus. The difference from FIG. 8 is that a snubber circuit is replaced with a semiconductor circuit S1 in place of a snubber capacitor 8 and a snubber capacitor 9 and a snubber diode 10 in series. The snubber module 11 is connected in parallel, and a snubber resistor 12 is connected between the connection point of the snubber capacitor 9 and the snubber diode 10 and the DC terminal on the opposite side of the inverter 3 to form a chargeable RCD snubber circuit for the inverter. It is the point which constitutes. The operation other than the snubber circuit and the charging current and charging voltage of the capacitor 7 are the same as those in the circuit of FIG. 8. In the snubber circuit, the snubber capacitor 9 is always connected to the DC voltage of the capacitor 1 via the snubber resistor 12. Since the same voltage is charged and the surge voltage generated when the semiconductor switch S1 is turned off becomes higher than the DC voltage of the capacitor 1, the snubber capacitor 9 is charged via the snubber diode 10, and this charge Is discharged to the original charging voltage of the capacitor 1 through the snubber resistor 12.

The prior art document information related to the present invention includes the following.
JP-A-8-140338 JP-A-6-14562 Japanese Patent Laid-Open No. 7-7924 Japanese Patent Laid-Open No. 6-169038 JP-A-10-285907

  In the conventional capacitor charging device described above, the snubber capacitor 8 is usually housed in a module filled with a molding material in order to prevent insulation deterioration due to moisture absorption and to keep insulation from other components. In order to reduce the inductance between the modularized snubber capacitor 8 and the semiconductor switches S1 and S2 as much as possible, as shown in FIG. 11, the electrode 8a of the snubber capacitor 8 is connected to the connection terminals 13 of the semiconductor switches S1 and S2. And so-called direct mounting structure. Reference numeral 14 denotes a cooling fin to which the semiconductor switches S1 and S2 are attached. However, there are mainly two factors for the temperature rise of the modularized snubber capacitor 8, one of which is that the heat generated in the semiconductor switches S1 and S2 and the conductor is modularized as indicated by the arrow 15 in FIG. This is transmitted to the snubber capacitor 8 and the temperature rises, and another factor is self-heating due to the influence of tan δ (dielectric loss tangent) inherent to the capacitor.

  The modularized snubber capacitor 8 dissipates heat generated by the above factors into the air through the molding material, but the molding material has low thermal conductivity, so that the cooling efficiency is poor. Therefore, in order to suppress the temperature rise, it is necessary to increase the number of parallel capacitors 8 or increase the surface area of the module in order to increase the cooling efficiency. As a result, the size of the modularized snubber capacitor 8 is increased. This led to a change in price and became expensive.

  In the snubber module 11 shown in FIG. 10, the snubber capacitor 9 and the snubber diode 10 are also housed in a module filled with a molding material, and the snubber module 11 has as much inductance as possible with the semiconductor switch S1. In order to reduce the number, the electrode 11a of the snubber module 11 is connected to the connection terminal 13 of the semiconductor switch S1 as shown in FIG. However, also in the snubber module 11, heat generated by the semiconductor switch S <b> 1 and the conductor is transferred to the snubber module 11 through a path as indicated by an arrow 16, and self-heating of the snubber capacitor 9 or self-heating due to loss of the snubber diode 10. The temperature rises and heat is dissipated through the molding material, but the heat dissipating effect is still bad, and it is necessary to increase the parallel number of the snubber capacitor 9 and the snubber diode 10 or increase the surface area of the snubber module 11. The snubber module 11 is large and expensive.

  The present invention has been made to solve the above problems, and can reduce the size and cost of a capacitor module containing a snubber capacitor, a metal case and a snubber capacitor, and a snubber module containing a snubber diode. It aims at obtaining the cooling structure of the snubber capacitor for inverters, and a snubber circuit.

  According to a first aspect of the present invention, there is provided a cooling structure for an inverter snubber capacitor, comprising: a plurality of semiconductor switches; and an inverter snubber capacitor connected in parallel to an inverter circuit for converting DC power to AC power. The capacitor is housed in a capacitor module filled with a molding material, and the electrode of the snubber capacitor and the conductor connected to the cooling fin for cooling the semiconductor switch are connected via a highly insulating and highly heat conductive sheet. Is.

The cooling structure of the inverter snubber circuit according to claim 2 is connected between the DC terminals and is composed of a plurality of semiconductor switches, and includes a snubber capacitor and a snubber in the semiconductor switch of the inverter circuit that converts DC power into AC power. For inverters consisting of a series circuit of diodes, connecting snubber modules filled with mold material in parallel, and connecting a snubber resistor between the connection point of the snubber capacitor and snubber diode and the DC terminal on the opposite side of the inverter circuit In a snubber circuit, a snubber diode and a conductor connected to a cooling fin for cooling a semiconductor switch are connected via a highly insulating and highly heat conductive sheet in a snubber module.

The cooling structure of the snubber circuit for an inverter according to claim 3 is such that the conductor is attached to the cooling fin with a screw, and this screw is attached to the upper surface or the side surface where the upper side of the cooling fin is opened.

According to a fourth aspect of the present invention, there is provided a cooling structure for an inverter snubber circuit including a plurality of semiconductor switches connected between DC terminals, and a semiconductor switch of an inverter circuit for converting DC power into AC power. For inverters consisting of a series circuit of diodes, connecting snubber modules filled with mold material in parallel, and connecting a snubber resistor between the connection point of the snubber capacitor and snubber diode and the DC terminal on the opposite side of the inverter circuit In the snubber circuit, the snubber diode in the snubber module, the electrode of the snubber module, and the conductor connected to the water pipe are connected via a highly insulating and highly heat conductive sheet.

  As described above, according to the first aspect of the present invention, the electrode of the snubber capacitor is connected to the cooling fin through the sheet and the conductor having high thermal conductivity, and the heat of the snubber capacitor is easily transmitted to the cooling fin. For this reason, the cooling effect of the snubber capacitor is improved, the temperature rise of the snubber capacitor is less likely to occur, there is no need to increase the number of snubber capacitors installed in parallel, and there is no need to increase the surface area of the capacitor module containing the snubber capacitor. Therefore, the capacitor module can be made small and inexpensive. Further, since the snubber capacitor is housed in the capacitor module filled with the molding material, there is no occurrence of insulation deterioration due to moisture absorption or the like.

According to claim 2 , in the snubber module filled with the molding material, the snubber diode and the conductor connected to the cooling fin are connected via the high thermal conductivity sheet, and the heat of the snubber diode is high thermal conductivity. It is transmitted to the cooling fin through the sheet and the conductor. For this reason, the thermal resistance between the snubber diode and the cooling fin is reduced, the snubber diode cooling effect is improved, the temperature rise of the snubber diode is less likely to occur, and there is no need to increase the number of snubber diodes installed in parallel, Since it is not necessary to increase the surface area of the snubber module containing the snubber diode, the snubber module can be reduced in size and cost. Further, since the snubber capacitor and the snubber module are housed in the snubber module filled with the mold material, insulation deterioration due to moisture absorption or the like does not occur.

In claim 3 lever, attached by screws to the conductor to the cooling fins, and attach the screw to the top surface or side upper is opened the cooling fins, when attached to the upper surface of the upper is opened, the mounting Workability is improved, and when it is attached to the side surface, attachment is facilitated when it cannot be attached to the upper surface.

According to the fourth aspect , the snubber diode in the snubber module is connected to the water pipe via the highly heat conductive sheet and conductor, and the snubber module electrode in the snubber module is connected to the highly heat conductive sheet and conductor. The heat of the snubber capacitor and snubber diode is transmitted to the water pipe through the sheet and the conductor. For this reason, the thermal resistance between the snubber capacitor / snubber diode and the water pipe is reduced, the cooling effect is improved, the temperature rise of the snubber capacitor / snubber diode is less likely to occur, and it is less susceptible to the ambient (air) temperature. Become. Therefore, it is not necessary to increase the number of parallel snubber capacitors and snubber diodes, and it is not necessary to increase the surface area of the snubber module containing the snubber capacitors and snubber diodes, and the snubber module can be reduced in size and cost. Further, since the snubber capacitor and the snubber diode are housed in the snubber module filled with the molding material, insulation deterioration does not occur due to moisture absorption or the like.

Best Embodiment 1
The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a cooling structure for a snubber capacitor for an inverter according to Embodiment 1 of the present invention. An electrode 8a of a snubber capacitor 8 is directly attached to a connection terminal 13 of semiconductor switches S1 and S2. The semiconductor switches S1 and S2 are attached to the cooling fins 14. Snubber capacitor 8 connected in parallel to the inverter circuits may molding material is accommodated in the capacitor module 17 which is filled. Further, the other end of the conductor 19 made of copper or the like attached to the cooling fin 14 with one end of the screw 18 is sandwiched between the electrode 8a of the snubber capacitor 8 and the highly heat conductive sheet 20 in the capacitor module 17. It is tightened by a plastic screw 21.

  In the first embodiment described above, the electrode 8a of the snubber capacitor 8 is connected to the cooling fin 14 via the sheet 20 and the conductor 19 having high thermal conductivity, and the heat of the snubber capacitor 8 flows along the path indicated by the arrow 22 in the cooling fin. 14 is transmitted. For this reason, the thermal resistance between the snubber capacitor 8 and the cooling fin 14 is reduced, the cooling effect is improved, the temperature of the snubber capacitor 8 is hardly increased, and the influence of the ambient (air) temperature is less likely to occur. Therefore, it is not necessary to increase the number of snubber capacitors 8 in parallel, and it is not necessary to increase the surface area of the capacitor module 17, so that the capacitor module 17 can be reduced in size and cost. Further, since the snubber capacitor 8 is housed in the capacitor module 17 filled with the molding material, insulation deterioration does not occur due to moisture absorption or the like.

Embodiment 2
FIG. 2 shows a configuration diagram of a cooling structure for a snubber capacitor for an inverter according to the second embodiment. Further, the other end of the conductor 19 made of copper or the like, one end of which is attached to the cooling fin 14 by a screw 18, is attached to the metal case 24 by screwing or brazing. The electrode 8a of the snubber capacitor 8 is inserted through the metal case 24 and connected to the connection terminals 13 of the semiconductor switches S1 and S2. An insulating material such as glass epoxy is used between the electrode 8a and the metal case 24. Insulate. Other configurations are the same as those of the prior art.

  In the second embodiment, the snubber capacitor 8 is housed in a metal case 24 in which an insulating oil 23 is enclosed, and the heat of the snubber capacitor 8 passes through the insulating oil 23 that has both insulating properties and high thermal conductivity. Conduction is conducted to the metal case 24, and further conducted to the cooling fin 14 as indicated by an arrow 22 through a conductor 19 connected to the metal case 24. For this reason, the thermal resistance between the snubber capacitor 8 and the cooling fin 14 is reduced, the cooling effect is improved, the temperature of the snubber capacitor 8 is hardly increased, and the influence of the ambient (air) temperature is less likely to occur. Therefore, it is not necessary to increase the number of snubber capacitors 8 in parallel, and it is not necessary to increase the surface area of the metal case 24, so that the metal case 24 can be reduced in size and cost. Further, since the snubber capacitor 8 is housed in the metal case 24 in which the insulating oil 23 is sealed, the insulation deterioration does not occur due to moisture absorption or the like.

Embodiment 3
FIG. 3 is a configuration diagram of a cooling structure of a snubber circuit for an inverter according to the third embodiment. A series circuit of a snubber capacitor 9 and a snubber diode 10 is housed in a snubber module 11 filled with a molding material. Are connected in parallel with the semiconductor switch S1. That is, the electrode 11a of the snubber module 11 is directly attached to the connection terminal 13 of the semiconductor switch S1. In addition, a snubber resistor 12 is connected between the connection point of the snubber capacitor 9 and the snubber module 10 and the DC terminal on the opposite side of the inverter circuit 3 to constitute a rechargeable RCD snubber circuit. One end of a conductor 19 made of copper or the like attached to the cooling fin 14 with a screw 18 at one end is a plastic screw 21 with a highly insulating and high thermal conductive sheet 20 sandwiched between the snubber diode 10 and the snubber module 11. It is tightened by.

  In the above-described third embodiment, the snubber diode 10 in the snubber module 11 is connected to the cooling fin 14 via the sheet 20 and the conductor 19 having high thermal conductivity, and the heat of the snubber diode 10 is in the path indicated by the arrow 22. It is transmitted to the cooling fin 14. For this reason, the thermal resistance between the snubber diode 10 and the cooling fin 14 is reduced, the cooling effect is improved, the temperature rise of the snubber diode 10 hardly occurs, and it is difficult to be affected by the ambient (air) temperature. Therefore, it is not necessary to increase the number of snubber diodes 10 in parallel, and it is not necessary to increase the surface area of the snubber module 11 in which the snubber capacitor 9 and the snubber diode 10 are housed, and the snubber module 11 can be reduced in size and cost. Further, since the snubber capacitor 9 and the snubber diode 10 are housed in the snubber module 11 filled with the molding material, insulation deterioration does not occur due to moisture absorption or the like.

Embodiment 4
FIG. 4 shows a configuration diagram of the cooling structure of the inverter snubber circuit according to the fourth embodiment. The difference from the third embodiment is that the position of the screw 18 for attaching one end of the conductor 19 to the cooling fin 14 is located above the cooling fin 14. As shown by an arrow 25, the upper surface is opened at a position accessible from above, and other configurations are the same as those in the third embodiment.

  In the fourth embodiment, since one end of the conductor 19 is attached to the upper surface of the cooling fin 14 with the screw 18 open, the attachment workability at the time of attachment can be improved.

Embodiment 5
FIG. 5 shows a configuration diagram of the cooling structure of the inverter snubber circuit according to the fifth embodiment. The difference from the third embodiment is that the position of the screw 18 for attaching one end of the conductor 19 to the cooling fin 14 is changed to the side surface of the cooling fin 14. The other configurations are the same as those of the third embodiment.

  In the fifth embodiment, since one end of the conductor 19 is attached to the side surface of the cooling fin 14 by the screw 18, when the one end of the conductor 19 cannot be attached to the upper surface of the cooling fin 14, the side surface of the cooling fin 14 is used. Can be easily installed.

Embodiment 6
FIG. 6 shows a configuration diagram of a cooling structure of a snubber circuit for an inverter according to the sixth embodiment. A series circuit of a snubber capacitor 9 and a snubber diode 10 is housed in a snubber module 11 filled with a molding material. Are connected in parallel with the semiconductor switch S1. That is, the electrode 11a of the snubber module 11 is directly attached to the connection terminal 13 of the semiconductor switch S1. In addition, a snubber resistor 12 is connected between the connection point of the snubber capacitor 9 and the snubber module 10 and the DC terminal on the opposite side of the inverter circuit 3 to constitute a rechargeable RCD snubber circuit. In the snubber module 11 filled with the molding material, the snubber diode 10 and one end of the conductor 19 are fastened by a plastic screw 21 via a highly insulating and highly heat-conductive sheet 20, and the electrodes of the snubber module 11. 11a and one end of the conductor 19 are fastened by a plastic screw 26 via a sheet 20 having high insulation and high thermal conductivity, and the other end of the conductor 19 is attached by a water pipe 27 and a screw 18 having a rectangular cross section.

  In the sixth embodiment, the snubber diode 10 in the snubber module 11 is connected to the water pipe 27 via the highly heat conductive sheet 20 and the conductor 19, and the electrode 11 a of the snubber module 11 in the snubber module 11 is heated to a high temperature. It is connected to the water pipe 27 through the conductive sheet 20 and the conductor 19, and the heat of the snubber capacitor 9 and the snubber diode 10 is transmitted to the water pipe 27 through the sheet 20 and the conductor 19 as indicated by an arrow 28. For this reason, the thermal resistance between the snubber capacitor 9 and the snubber diode 10 and the water pipe 27 is reduced, the cooling effect is improved, the temperature rise of the snubber capacitor 9 and the snubber diode 10 is less likely to occur, and the ambient (air) temperature. It becomes difficult to be affected. Therefore, it is not necessary to increase the parallel number of the snubber capacitor 9 and the snubber diode 10, and it is not necessary to increase the surface area of the snubber module 11 that houses the snubber capacitor 9 and the snubber diode 10. Can do. Further, since the snubber capacitor 9 and the snubber diode 10 are housed in the snubber module 11 filled with the molding material, insulation deterioration does not occur due to moisture absorption or the like. The sixth embodiment is highly effective when the temperature of the water pipe 27 is lower than the temperature of the cooling fin 14.

Embodiment 7
FIG. 7 shows a configuration diagram of the cooling structure of the inverter snubber circuit according to the seventh embodiment, and the difference from the sixth embodiment is that the other end of the conductor 19 is brazed to a water pipe 29 having a circular cross section. . Other configurations are the same as those of the sixth embodiment. The effect is that the other end of the conductor 19 and the water pipe 29 are brazed, so that the contact thermal resistance can be reduced. The other effect is the same as in the sixth embodiment. In the case of Embodiment 7 as well, the effect is great when the temperature of the water pipe 29 is lower than the temperature of the cooling fin 14.

It is a block diagram of the cooling structure of the snubber capacitor for inverters by Embodiment 1 of this invention. It is a block diagram of the cooling structure of the snubber capacitor for inverters by Embodiment 2. It is a block diagram of the cooling structure of the snubber circuit for inverters by Embodiment 3. It is a block diagram of the cooling structure of the snubber circuit for inverters by Embodiment 4. It is a block diagram of the cooling structure of the snubber circuit for inverters by Embodiment 5. It is a block diagram of the cooling structure of the snubber circuit for inverters by Embodiment 6. It is a block diagram of the cooling structure of the snubber circuit for inverters by Embodiment 7. It is a circuit block diagram of the conventional capacitor | condenser charging device. It is a voltage-current characteristic figure of the conventional capacitor | condenser charging device. It is a circuit block diagram of the other conventional capacitor | condenser charging device. It is a principal part structure figure of the capacitor | condenser charging device shown in FIG. It is a principal part structure figure of the capacitor | condenser charging device shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Inverter circuit 8,9 ... Snubber capacitor 8a, 11a ... Electrode 10 ... Snubber diode 11 ... Snubber module 12 ... Snubber resistance 13 ... Semiconductor switch connection terminal 14 ... Cooling fin 17 ... Capacitor module 18 ... Screw 19 ... Conductor 20 ... Sheet 21, 26 ... Plastic screw 23 ... Insulating oil 24 ... Metal case 27, 29 ... Water piping S1, S2 ... Semiconductor switch

Claims (4)

  In a snubber capacitor for an inverter that is composed of a plurality of semiconductor switches and is connected in parallel to an inverter circuit that converts DC power to AC power, the snubber capacitor is housed in a capacitor module filled with a mold material, A cooling structure for a snubber capacitor for an inverter, wherein a capacitor electrode and a conductor connected to a cooling fin for cooling a semiconductor switch are connected via a highly insulating and highly heat conductive sheet. A snubber connected between DC terminals and composed of a plurality of semiconductor switches, which is a series circuit of a snubber capacitor and a snubber diode in a semiconductor switch of an inverter circuit that converts DC power into AC power, and is filled with a molding material. In a snubber circuit for an inverter in which a module is connected in parallel and a snubber resistor is connected between the connection point between the snubber capacitor and the snubber diode and the DC terminal on the opposite side of the inverter circuit, the snubber diode and the semiconductor switch are connected in the snubber module. A cooling structure of a snubber circuit for an inverter, wherein a conductor connected to a cooling fin to be cooled is connected via a highly insulating and highly heat conductive sheet . 3. The inverter snubber circuit cooling structure according to claim 2, wherein the conductor is attached to the cooling fin with a screw, and the screw is attached to an upper surface or a side surface of the cooling fin that is open on the upper side . A snubber connected between DC terminals and composed of a plurality of semiconductor switches, which is a series circuit of a snubber capacitor and a snubber diode in a semiconductor switch of an inverter circuit that converts DC power into AC power, and is filled with a molding material. In a snubber circuit for an inverter in which the modules are connected in parallel and a snubber resistor is connected between the connection point between the snubber capacitor and the snubber diode and the DC terminal on the opposite side of the inverter circuit, the snubber diode and snubber module in the snubber module are connected. A cooling structure of a snubber circuit for an inverter, wherein an electrode and a conductor connected to a water pipe are connected via a highly insulating and highly heat conductive sheet .

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