JP2015198483A - Bi-directional dc/dc converter for industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bi-directional DC/DC converter for an industrial vehicle which inhibits temperature rise of a current sensor CT.SOLUTION: In a bi-directional DC/DC converter 110 for an industrial vehicle, an upper arm and a lower arm are incorporated into a power module IPM. A current sensor CT is electrically provided between an inductor L1 and the power module IPM. The power module IPM and the inductor L1 are mounted on a bottom surface of a housing 200. A plate 220 is mounted with the current sensor CT adhering to a first surface of the plate 220. The plate 220 is detachably attached to the housing 200 with a second surface of the plate 220 adhering to a side wall of the housing 200.

Description

  The present invention relates to a bidirectional DC / DC converter mounted on an industrial vehicle.

  In recent construction machines such as power shovels and cranes, a hybrid type of a hydraulic motor and an AC motor is used as a power source for the upper swing body. The hybrid-type turning power source assists the hydraulic motor with an AC motor during acceleration of the upper turning body, performs a regenerative operation with the AC motor during deceleration, and charges a storage battery such as a battery with generated energy.

  In order to mutually transfer energy between the AC motor and the battery, a power supply device using a bidirectional DC / DC converter (also referred to as a step-up / down converter) is provided. FIG. 1 is a circuit diagram showing a basic configuration of the power supply apparatus 100r. The power supply device 100r includes a capacitor 102, a DC bus 104, a bidirectional DC / DC converter 110, and a controller 120.

The battery 102 is connected to the primary side of the bidirectional DC / DC converter 42, and the DC bus 104 is connected to the secondary side thereof. An inverter 18 is connected to the DC bus 104. Inverter 18 converts the voltage of the DC bus 104 (DC link _{voltage) V DC} to an AC voltage to drive the motor 12.

  The bidirectional DC / DC converter 110 includes an inductor (reactor) L1, a smoothing capacitor C1, an upper arm (transistor) M1, a lower arm M2, and a current sensor CT. Since the topology of the bidirectional DC / DC converter 110 is known, the description thereof is omitted. The transistors M1 and M2 are built in one power module (IPM: Intelligent Power Module).

  In order to increase the current capacity, a plurality of power modules IPM1 and IPM2 are provided in parallel, and inductors (reactors) L1_1 and L1_2 are provided for each of the power modules IPM1 and IPM2. Current sensors CT1 and CT2 are provided for each of the inductors L1_1 and L1_2, and each detects a current flowing through the corresponding inductor L1.

The controller 120 receives a voltage command Vr indicating a target value of the voltage (DC link voltage) _VDC of the DC bus 104 from an upstream controller. Current detection values indicating currents flowing through the inductors L1_1 and L1_2 are received from the current sensors CT1 and CT2. The controller 120 controls the switching duty ratio of the transistors M1 and M2 so that the DC link voltage V _DC matches the voltage command Vr, and adjusts the converter current that is the sum of the currents flowing through the inductors L1_1 and L1_2.

  FIG. 2 is a cross-sectional view showing a layout of the bidirectional DC / DC converter 110r examined by the present inventors. The components of the bidirectional DC / DC converter 110 are built in the housing 200. FIG. 2 shows only the bottom surface of the housing 200.

  The power module IPM and the inductor L1 are mounted on the bottom surface of the housing 200. Inductors L1_1 and L1_2 are covered with a cover 201 in order to prevent the heat generated by the inductor L1 from adversely affecting the surroundings. The inductor L1 and the power module IPM are connected via the bus bar 206.

  The current sensor CT is mounted on the cover 201 just above the corresponding inductor L1. The current sensor CT and the inductor L1 are connected by a bus bar 204 extending in the vertical direction. The current sensor CT is connected to the battery 102 (not shown) via the bus bar 202.

JP 2012-253594 A JP 2011-135725 A

As a result of studying the layout of FIG. 2, the present inventor has recognized the following problems.
In the bidirectional DC / DC converter 110r, when a large current flows through the inductor L1, the amount of generated heat increases. In the layout of FIG. 2, since the current sensor CT is provided immediately above the inductor L1, the influence of the heat of the inductor L1 reaches the current sensor CT. When the current sensor CT is exposed to high heat, there is a problem that the detection accuracy is deteriorated and the performance of the bidirectional DC / DC converter 110 is deteriorated. In particular, an excavator is required to operate normally at an ambient temperature of 70 degrees. In the layout of FIG. 2, when the current sensor CT is heated by the inductor L1 in an environment at an ambient temperature of 70 degrees, the operation of the current sensor CT is performed. The guaranteed temperature may be exceeded. Such a problem should not be regarded as a general recognition of those skilled in the art.

  An aspect of the present invention has been made in view of such problems, and one of exemplary purposes of the aspect is to provide a bidirectional DC / DC converter for an industrial vehicle capable of suppressing a temperature increase of the current sensor CT. On offer.

  An aspect of the present invention relates to a bidirectional DC / DC converter for an industrial vehicle. The bidirectional DC / DC converter includes a power module in which an upper arm and a lower arm are built-in, an inductor, a current sensor that detects a current flowing through the inductor, a casing on which the power module and the inductor are mounted, And a plate that is mounted in a manner in which the current sensor is in close contact with the first surface, and is detachably attached to the housing in a manner in which the second surface is in close contact with the side wall of the housing.

  According to this aspect, the current sensor can be brought into close contact with the side wall of the casing through the plate, whereby the heat of the current sensor can be released to the casing, and the temperature increase of the current sensor can be suppressed.

The current sensor may be electrically provided between the inductor and the power module.
Thereby, the current sensor can be kept away from the inductor during layout.

The current sensor may be disposed immediately above the power module, and the current sensor and the power module may be electrically connected via a bus bar extending in the vertical direction.
Thereby, at the time of layout, the current sensor can be moved away from the inductor in the planar direction and in the high direction.

  The plate may have two opposing surfaces, and the cross section may have a substantially U-shape. The current sensor may be mounted on the first surface, and the second surface may be in close contact with the housing. .

  Thermal grease may be applied between the plate and the current sensor and between the plate and the housing. The thermal resistance of the contact surface can be reduced by the thermal grease.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  According to the present invention, the temperature rise of the current sensor CT can be suppressed.

It is a circuit diagram which shows the basic composition of a power supply device. It is sectional drawing which shows the layout of the bidirectional | two-way DC / DC converter which this inventor examined. It is a perspective view which shows the external appearance of the shovel which is an example of the construction machine which concerns on embodiment. It is a block diagram, such as an electric system and a hydraulic system, of the excavator according to the embodiment. It is a circuit diagram of the power supply device concerning an embodiment. It is sectional drawing which shows the layout of the bidirectional | two-way DC / DC converter of FIG.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  FIG. 3 is a perspective view showing an appearance of an excavator 1 that is an example of the construction machine according to the embodiment. The excavator 1 mainly includes a traveling mechanism 2 and an upper revolving body (hereinafter also simply referred to as a revolving body) 4 that is rotatably mounted on the upper portion of the traveling mechanism 2 via a revolving mechanism 3.

  The revolving body 4 is attached with a boom 5, an arm 6 linked to the tip of the boom 5, and a bucket 10 linked to the tip of the arm 6. The bucket 10 is a facility for capturing suspended loads such as earth and sand and steel materials. The boom 5, the arm 6, and the bucket 10 are hydraulically driven by a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9, respectively. Further, the revolving body 4 is provided with a power source such as a driver's cab 4a for accommodating an operator who operates the position of the bucket 10, excitation operation and release operation, and an engine 11 for generating hydraulic pressure. The engine 11 is composed of, for example, a diesel engine.

  FIG. 4 is a block diagram of an electric system and a hydraulic system of the excavator 1 according to the present embodiment. In FIG. 4, a system for mechanically transmitting power is indicated by a double line, a hydraulic system is indicated by a thick solid line, a control system is indicated by a broken line, and an electric system is indicated by a thin solid line.

  The excavator 1 includes a motor generator 12 and a speed reducer 13, and the rotation shafts of the engine 11 and the motor generator 12 are connected to each other by being connected to the input shaft of the speed reducer 13. When the load of the engine 11 is large, the motor generator 12 assists (assists) the driving force of the engine 11 with its own driving force, and the driving force of the motor generator 12 passes through the output shaft of the speed reducer 13 to the main pump 14. Communicated. On the other hand, when the load on the engine 11 is small, the driving force of the engine 11 is transmitted to the motor generator 12 via the speed reducer 13, so that the motor generator 12 generates power. The motor generator 12 is configured by, for example, an IPM (Interior Permanent Magnetic) motor in which a magnet is embedded in the rotor. Switching between driving of the motor generator 12 and power generation is performed by the controller 30 that controls driving of the electric system in the excavator 1 according to the load of the engine 11 and the like.

  A main pump 14 and a pilot pump 15 are connected to the output shaft of the speed reducer 13, and a control valve 17 is connected to the main pump 14 via a high pressure hydraulic line 16. The control valve 17 is a device that controls the hydraulic system in the excavator 1. In addition to hydraulic motors 2A and 2B for driving the traveling mechanism 2 shown in FIG. 3, a boom cylinder 7, an arm cylinder 8 and a bucket cylinder 9 are connected to the control valve 17 via a high pressure hydraulic line. The control valve 17 controls the hydraulic pressure supplied to them according to the operation input of the driver.

  An operation device 26 (operation means) is connected to the pilot pump 15 via a pilot line 25. The operating device 26 is an operating device for operating the turning electric motor 21, the traveling mechanism 2, the boom 5, the arm 6, and the bucket 10, and is operated by an operator. A control valve 17 is connected to the operating device 26 via a hydraulic line 27, and a pressure sensor 29 is connected via a hydraulic line 28. The operating device 26 converts the hydraulic pressure (primary hydraulic pressure) supplied through the pilot line 25 into a hydraulic pressure (secondary hydraulic pressure) corresponding to the operation amount of the operator and outputs the hydraulic pressure. The secondary hydraulic pressure output from the operating device 26 is supplied to the control valve 17 through the hydraulic line 27 and detected by the pressure sensor 29.

  When an operation for turning the turning mechanism 3 is input to the operating device 26, the pressure sensor 29 detects this operation amount as a change in the oil pressure in the hydraulic line 28. The pressure sensor 29 outputs an electrical signal indicating the hydraulic pressure in the hydraulic line 28. This electric signal is input to the controller 30 and used for driving control of the turning electric motor 21.

  The controller 30 is configured by an arithmetic processing unit including a CPU (Central Processing Unit) and an internal memory, and is realized by the CPU executing a drive control program stored in the internal memory. The controller 30 receives operation inputs from various sensors and the operation device 26, and performs drive control of the inverters 18A, 18B, 18C, the power storage means 101, and the like.

  The hydraulic motor 310 is configured to be rotated by oil discharged from the boom cylinder 7 when the boom 5 is lowered, and is provided to convert energy when the boom 5 is lowered according to gravity into rotational force. It has been. The hydraulic motor 310 is provided in the hydraulic pipe 7 </ b> A between the control valve 17 and the boom cylinder 7. The electric power generated by the boom regenerative generator 300 is supplied as regenerative energy to the power storage means 101 via the inverter 18B.

  The turning electric motor 21 is provided in the turning mechanism 3 of FIG. 3 and rotates the upper turning body 4. The turning electric motor 21 is an AC electric motor and is a power source of the turning mechanism 3 for turning the turning body 4. A resolver 22, a mechanical brake 23, and a turning speed reducer 24 are connected to the rotating shaft 21 </ b> A of the turning electric motor 21. The turning inverter 18 </ b> C receives electric power from the power storage means 101 and drives the turning electric motor 21. Further, during the regenerative operation of the turning electric motor 21, the electric power from the turning electric motor 21 is collected in the power storage means 101.

  When the turning electric motor 21 performs a power running operation, the rotational force of the rotational driving force of the turning electric motor 21 is amplified by the turning speed reducer 24, and the turning body 4 is subjected to acceleration / deceleration control to perform rotational motion. Further, due to the inertial rotation of the swing body 4, the rotation speed is increased by the swing speed reducer 24 and transmitted to the swing electric motor 21 to generate regenerative power.

  The resolver 22 is a sensor that detects the rotation position and rotation angle of the rotation shaft 21A of the turning electric motor 21, and mechanically connects to the turning electric motor 21 to detect the rotation angle and rotation direction of the rotation shaft 21A. When the resolver 22 detects the rotation angle of the rotation shaft 21A, the rotation angle and the rotation direction of the turning mechanism 3 are derived. The mechanical brake 23 is a braking device that generates a mechanical braking force, and mechanically stops the rotating shaft 21 </ b> A of the turning electric motor 21 according to a command from the controller 30. The turning speed reducer 24 is a speed reducer that reduces the rotational speed of the rotating shaft 21 </ b> A of the turning electric motor 21 and mechanically transmits it to the turning mechanism 3.

  Next, the electric system will be described in detail. The electric system mainly includes a controller 30, a power supply device 100, and inverters 18A to 18C.

(assist)
The motor generator 12 is connected to the secondary side (output) end of the assist inverter 18A. The inverter 18A controls the operation of the motor generator 12 based on a command from the assist inverter controller 30A that is a part of the controller 30.

(Boom regeneration)
A boom regeneration generator 300 is connected to the secondary side (output) end of the inverter 18B. As described above, the boom regeneration generator 300 is an electric working element that converts potential energy into electrical energy when the boom 5 is lowered by the action of gravity. The inverter 18 </ b> B is controlled by the boom regeneration inverter controller 30 </ b> B of the controller 30, converts the electric energy generated by the boom regeneration generator 300 into DC power, and recovers it to the power supply device 100.

(Turning)
The turning electric motor 21, the resolver 22, the mechanical brake 23, the turning speed reducer 24, the turning inverter 18 </ b> C and the turning inverter controller 30 </ b> C that is a part of the controller 30 constitute an electric turning device 500.
The turning electric motor 21 is AC driven by the turning inverter 18C in accordance with a PWM (Pulse Width Modulation) control command. As the turning electric motor 21, for example, a magnet-embedded IPM motor is suitable.

  The turning inverter controller 30C receives a rotation speed command corresponding to the operation input, and controls the turning inverter 18C so that the turning speed of the turning electric motor 21 detected by the resolver 22 matches the rotation speed command.

(Power supply)
The power storage device 101 and the converter controller 30 </ b> D that is a part of the controller 30 constitute the power supply device 100. The power storage means 101 includes, for example, a battery as a storage battery, a step-up / down converter (bidirectional DC / DC converter) that controls charging / discharging of the battery, and a DC bus including positive and negative DC wirings (not shown). ) As the electric storage device, a rechargeable secondary battery such as a lithium ion battery, a capacitor, or any other form of power source capable of transferring power may be used. The primary side (DC input) of each of the inverters 18A to 18C is connected to the DC bus. The controller 30D controls the bidirectional DC / DC converter so that the DC link voltage generated on the DC bus becomes a predetermined voltage level. The power supply apparatus 100 boosts the bidirectional DC / DC converter when the motor generator 12 or the like performs a power running operation, and steps down the bidirectional DC / DC converter when the motor generator 12 or the like performs a regenerative operation. The electric power generated by the motor generator 12 is collected in the battery.

  That is, when the inverter 18A causes the motor generator 12 to perform a power running operation, necessary power is supplied from the battery and the step-up / down converter to the motor generator via the DC bus. When the motor generator 12 is regeneratively operated, the battery is charged with the electric power generated by the motor generator 12 via the DC bus and the step-up / down converter. The switching control between the step-up / step-down converter and the step-down operation is performed by the converter controller 30D based on the DC bus voltage value, the battery voltage value, and the battery current value. As a result, the DC bus can be maintained in a state of being stored at a predetermined constant voltage value.

  The above is the overall configuration of the excavator 1. Next, the power supply device 100 will be described in detail.

FIG. 5 is a circuit diagram of the power supply device 100 according to the embodiment.
The power supply apparatus 100 includes a battery 102, a DC bus 104, a bidirectional DC / DC converter 110, and a converter controller (hereinafter simply referred to as a controller) 120.
The battery 102 is a battery or a large capacity capacitor. Although the inverters 18A to 18C can be connected to the DC bus 104, only the inverter 18A is shown in FIG. 5 for easy understanding and simplification of description.

  The battery 102 is connected to the primary side of the bidirectional DC / DC converter 110, and the DC bus 104 is connected to the secondary side. The bidirectional DC / DC converter 110 is configured to be able to exchange energy bidirectionally between the primary side and the secondary side. When the motor generator 12 performs a power running operation, the bidirectional DC / DC converter 110 performs a step-up operation, and a charging current is supplied from the capacitor 102 via the inductor L1 and the transistor M1 to charge the smoothing capacitor C1. When the motor generator 12 performs a regenerative operation, the bidirectional DC / DC converter 110 performs a step-down operation, and the regenerative current generated by the motor generator 12 is recovered in the battery 102 via the transistor M1 and the inductor L1.

The controller 120 controls the bidirectional DC / DC converter 110 so that the DC link voltage V _DC generated in the DC bus 104 approaches a predetermined target voltage Vr. Specifically, the switching duty ratio of the transistors M1 and M2 is controlled so that the DC link voltage V _DC matches the voltage command Vr, and the converter current that is the sum of the currents flowing through the inductors L1_1 and L1_2 is adjusted.

For example, the controller 120 may include the following configuration.
Voltage controller: Generates a current command that is adjusted so that the DC link voltage V _DC matches the voltage command Vr.
Current controller: Generates a duty command in which the converter current Ic indicated by the outputs of the plurality of current sensors CT is adjusted to match the current command.
Pulse width modulator: Generates a pulse signal having a duty ratio corresponding to a duty command.
Gate driver: Drives the transistors M1 and M2 of the power module according to the pulse signal.

  It should be noted that in the present embodiment, the position of the current sensor CT is different from that of FIG. Specifically, in the present embodiment, the current sensor CT is provided between the inductor L1 and the power module IPM.

6 is a cross-sectional view showing a layout of the bidirectional DC / DC converter 110 of FIG. FIG. 6 shows only a portion corresponding to one power module.
The bidirectional DC / DC converter 110 includes a housing 200, a power module IPM, an inductor L1, a current sensor CT, an insulation support 222, thermal grease 224, and bus bars 210 and 212.

  The housing 200 accommodates the components of the bidirectional DC / DC converter 110. In addition to the bidirectional DC / DC converter 110, the casing 200 may house the components of the inverter 18 and the controller 120.

A power module IPM and an inductor L1 are mounted on the bottom surface _{SBTM of the} housing 200. The casing 200 is provided with a cooling mechanism (not shown), for example, a water cooling mechanism, and its temperature rise is suppressed. Thereby, the power module IPM and the inductor L1 can be cooled via the housing 200.

  The plate 220 is made of a metal having high thermal conductivity, such as copper or aluminum. For example, the plate 220 has a substantially U-shaped cross section, and thus has two opposing surfaces S1 and S2. The plate 220 may be produced by bending a single metal plate, or may be produced by welding or screwing a plurality of metal plates. The plate 220 may be a block-shaped member.

On the first surface S1 of the plate 220, the current sensor CT1 is mounted in a closely contacted state, in other words, in a state where it is thermally and strongly coupled. The plate 220 is attached to the housing 200 in close contact so that the second surface S2 is thermally strongly coupled to the side wall S _SIDE of the housing 200. Thermal grease 226 is preferably applied between the current sensor CT and the plate 220, and similarly, it is desirable to apply thermal grease 224 between the plate 220 and the side wall S _SIDE of the housing 200.

The bottom of the insulating support 222 is fixed to the bottom surface _SBTM of the housing 200. The insulating support 222 supports and fixes the plate 220. The plate 220 and the insulating support 222 are detachably screwed.

  The power module IPM, the inductor L1, and the current sensor CT are electrically connected by bus bars 210 and 212.

The above is the configuration of the bidirectional DC / DC converter 110.
In this bidirectional DC / DC converter 110, the current sensor CT is arranged on the gate side of the power module IPM on the equivalent circuit as shown in FIG. As a result, the position of the current sensor CT can be physically moved away from the inductor L1 during layout. Specifically, as shown in FIG. 6, on the projection surface onto the bottom surface _{SBTM of the} housing 200. The heater L1 is disposed at a position away from the inductor L1, which is a heating element. Thereby, it can suppress that the influence of the heat | fever of the inductor L1 reaches current sensor CT, and can suppress the temperature rise of current sensor CT.

Further, by bringing the current sensor CT into close contact with the sidewall S _SIDE of the housing 200 via the plate 220, the heat of the current sensor CT can be released to the housing 200, and the temperature rise of the current sensor CT can be suppressed.

Here, it is conceivable that the current sensor CT is directly mounted on the side wall S _{SIDE of the} housing 200 without using the plate 220. However, in an industrial vehicle such as the excavator 1, maintenance is required. Specifically, each component is required to be easily accessed and replaced. Mounting the current sensor CT directly on the side wall S _SIDE is not preferable from the viewpoint of maintainability.

  In contrast, when the current sensor CT is mounted on the plate 220 as shown in FIG. 6 and the plate 220 is attached to the housing 200, the current sensor CT is inspected or replaced. Since it can be attached and detached, it is advantageous from the viewpoint of maintainability.

  Further, by applying the thermal grease 224 and the thermal grease 226, the thermal resistance at the contact surface can be lowered.

  In the above, this invention was demonstrated based on the Example. It is understood by those skilled in the art that the present invention is not limited to the above-described embodiment, and various design changes are possible, and various modifications are possible, and such modifications are within the scope of the present invention. It is a place. Hereinafter, such modifications will be described.

  In the embodiment, the excavator 1 is shown as an example of the hybrid-type construction machine according to the present invention. However, as another example of the hybrid-type construction machine of the present invention, a lifting magnet vehicle, a crane, or the like having a turning mechanism is given. It is done.

DESCRIPTION OF SYMBOLS 1 ... Excavator, 2 ... Traveling mechanism, 2A ... Hydraulic motor, 3 ... Turning mechanism, 4 ... Turning body, 4a ... Driver's cab, 5 ... Boom, 6 ... Arm, 7 ... Boom cylinder, 7A ... Hydraulic pipe, 8 ... Arm Cylinder, 9 ... Bucket cylinder, 10 ... Bucket, 11 ... Engine, 12 ... Motor generator, 13 ... Reduction gear, 14 ... Main pump, 15 ... Pilot pump, 16 ... High pressure hydraulic line, 17 ... Control valve, 18, 18A , 18B ... inverter, 18C ... turning inverter, 21 ... turning electric motor, 21A ... rotating shaft, 22 ... resolver, 23 ... mechanical brake, 24 ... turning speed reducer, 25 ... pilot line, 26 ... operating device, 27, 28 ... Hydraulic line, 29 ... Pressure sensor, 30 ... Controller, 30A, 30B, 30C ... Inverter controller, 30D ... Converter 100, power supply device, 101 ... power storage means, 102 ... capacitor, 104 ... DC bus, 110 ... bi-directional DC / DC converter, C1 ... smoothing capacitor, L1 ... inductor, 120 ... controller, 200 ... casing, 210, DESCRIPTION OF SYMBOLS 212 ... Bus bar, 220 ... Plate, 222 ... Insulation support, 224, 226 ... Thermal grease, CT ... Current sensor, IPM ... Power module, 300 ... Boom regeneration generator, 310 ... Hydraulic motor, 500 ... Electric turning device

Claims (5)

A bidirectional DC / DC converter for industrial vehicles,
A power module with built-in upper and lower arms;
An inductor;
A current sensor for detecting a current flowing through the inductor;
A casing on which the power module and the inductor are mounted on the bottom surface;
A plate that is mounted in a manner in which the current sensor is in close contact with the first surface, and that is detachably attached to the housing in a manner in which the second surface is in close contact with the side wall of the housing;
A bidirectional DC / DC converter for industrial vehicles, comprising:   The bidirectional DC / DC converter for industrial vehicles according to claim 1, wherein the current sensor is electrically provided between the inductor and the power module.   The industrial vehicle according to claim 2, wherein the current sensor is disposed immediately above the power module, and the current sensor and the power module are electrically connected via a bus bar extending in a vertical direction. Bidirectional DC / DC converter. The plate has two opposing surfaces, and has a substantially U-shaped cross section.
The bidirectional DC / DC converter for industrial vehicles according to any one of claims 1 to 3, wherein the current sensor is mounted on a first surface, and the second surface is in close contact with the housing.   5. The industrial vehicle bidirectional DC / according to claim 1, wherein thermal grease is applied between the plate and the current sensor, and between the plate and the housing. DC converter.

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