JP2001286152A - Grounding structure for inverter system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a trouble in a neighboring equipment by enabling to limit the earth current to a floor and the like even when an equipment is installed on a conductive floor or structure. SOLUTION: A grounding structure for an inverter system has a constitution wherein, when an inverter-unit box 2 housing an inverter unit 1 and a box 4 of a motor 3 that is driven by an output of the inverter unit are installed on the conductive floor or structure 5, an insulating material 41 is laid between the inverter-unit box and the conductive floor or structure, each earth terminal 1E, 2E of the inverter-unit box and the box of the motor is connected to each other by a conductive member 43, and an inductance 42 is connected in series to the earth terminal 1E of the inverter-unit box.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grounding structure of an inverter system which is effective when an inverter system is installed on a conductive floor or a structure. The present invention relates to a grounding structure of an inverter system for suppressing a ground current flowing through a structure.

[0002]

2. Description of the Related Art The grounding of a conventional inverter system is performed by connecting a housing of an inverter having an inverter circuit and the like and a housing of a motor driven by the output of the inverter to a ground electrode via a ground wire. Is common.

FIG. 4 is a view for explaining a grounding structure of a conventional general inverter system. In this inverter system, an inverter device housing 2 containing an inverter device 1 and a motor housing 4 housing a motor 3 to be controlled are installed on a floor 5. 3 is connected to a cable 6 for supplying electric power. The inverter device 1 includes a rectifier 11, a filter circuit 12, an inverter circuit 13 including a switching element, and the like. The electric motor 3 is provided with an electric motor stator winding 31 which is a component of the electric motor.

Further, as a grounding system of the inverter system, a portion of each of the housings 2 and 4 is connected to ground terminals 1E and 2E.
Ground wires 14 and 32 are individually led out of the ground terminals 1E and 2E, and are connected to the ground poles 15 and 33 of the floor 5, respectively.

By the way, in an inverter device using a high-speed switching element represented by IGBT, GTO, etc.,
As the switching element constituting the inverter circuit 13 repeats the switching operation, the potential of the cable 6 on the output side of the inverter device and the electric motor stator winding 31 with respect to the ground changes. As a result, the motor stator winding 3
A stray capacitance Cs exists between the motor 1 and the motor casing 4. The ground current is flows into the floor surface through the motor casing 4 by charging and discharging the stray capacitance Cs. This earth current is is supplied with energy from inside the inverter device 1 by switching of the inverter circuit 13, and eventually becomes a current returning to the inverter circuit 13.

In the inverter device 1, a stray capacitance Ci similarly exists between the inverter device 1 and the inverter device housing 2, and when the power supply of the inverter device 1 is a non-grounded system, the stray capacitance Ci is grounded. The current is flows and returns to the inverter circuit 13. When the power supplied to the inverter device 1 is grounded, the ground current is may return to the inverter circuit 13 through this ground circuit.

[0007]

The inverter system is generally installed on a floor 5 made of concrete or the like. However, the inverter system may be a conductive floor 5 or a steel frame of a building due to restrictions on the installation place of the inverter system. It is often attached to a steel plate structure such as a ship or a vehicle, or to a structure such as a metal housing.

On the other hand, as described above, the ground current does not always flow through the ground wires 14 and 32 to the ground poles 15 and 33. Even more, when the inverter system is installed on a conductive floor or structure, Usually, the inverter housing 2, the motor housing 4, and the like, and the conductive floor 5 and the structure are in contact with each other, and are often in a so-called conductive state. As a result, for example, even if the ground terminal 2E of the motor housing 4 is connected to the ground electrode 33, not all ground current necessarily flows into the ground electrode 33. Flow through. The same applies to the inverter device 1. Even if the ground terminal 1 </ b> E of the inverter device housing 2 is connected to the ground electrode 15, the ground current does not necessarily flow into the ground electrode 15.

Therefore, as described above, the earth current often flows through the stray capacitance between the inverter device 1, the cable 6, the motor 3, and the housings 2, 4, etc., so that the current path is artificially controlled. It is difficult to do so, and if the ground potential fluctuates, it may cause a malfunction such as a malfunction in peripheral devices.

[0010] In particular, the more the switching element itself has high performance and high-speed switching operation, the more the earth current accompanying the high-speed switching by the inverter device 1 becomes.
It is clear that high frequencies and large currents will occur, and this is a very important problem given that the inverter system is moving toward higher voltages and higher capacities in the future.

Since structures such as buildings are not originally constructed for the purpose of flowing current, it is desirable to supply a large earth current to these structures from the viewpoint of human and structural safety. is not.

The present invention has been made in view of the above circumstances, and suppresses the flow of ground current to these floors and the like even when it is mounted on a conductive floor or a structure, thereby preventing peripheral equipment from being damaged. It is an object of the present invention to provide a grounding structure for an inverter system.

It is another object of the present invention to provide a grounding structure for an inverter system that ensures stable operation of an inverter device and safety of personnel and structures.

[0014]

(1) In order to solve the above problems, a grounding structure of an inverter system according to the present invention comprises an inverter device housing including an inverter device including a switching element and the inverter device. When the housing of the motor driven by the output of the inverter is installed on a conductive floor or structure, an insulating material is interposed between the inverter device housing and the conductive floor or structure, and This is a structure in which a high-frequency current limiting element is connected in series to a ground terminal of an inverter device housing and grounded.

With the above-described structure, the present invention prevents the earth current from flowing directly to the floor due to the insulating material, thereby ensuring safety for humans and structures, and at the high speed switching of the inverter device. Even if a high-frequency current flows, it is limited by the high-frequency current limiting element, and the DC potential of the inverter device housing can be set to the same level as the ground line.

(2) The grounding structure of the inverter system according to the present invention has a structure in which an insulating material is interposed between a conductive floor or a structure and an inverter device housing and a motor housing. Each ground terminal is connected to each other by a conductive member, and a high-frequency current limiting element is connected in series to the ground terminal of the inverter device housing to be grounded, thereby having the same operation as the above item (1).
By connecting the ground terminals of the inverter device housing and the motor housing to each other with a conductive member, ground current flows through the conductive member, so that no potential is applied to the high-frequency current limiting element, and as a result, stable operation of the inverter device Becomes possible.

(3) In the present invention, not only is a conductive member connected between the ground terminal of the inverter device housing and the ground terminal of the motor housing, but also a low-frequency current limiting element is connected to the conductive member. Are connected in series, it is possible to suppress or cut off harmful low-frequency currents such as an induced current having an operating frequency component of the inverter device.

(4) In the grounding structure of the inverter system according to the present invention, the inverter device housing including the inverter device including the switching element and the motor housing driven by the output of the inverter device are electrically conductive. When the neutral point of the transformer, which is installed on the floor or structure of the inverter and forms a power supply for supplying power to the inverter device, is grounded, the connection between the inverter device housing and the conductive floor or structure An insulating material is interposed therebetween, and a high-frequency current limiting element is connected in series to the ground terminal of the inverter device housing and grounded, and the neutral point of the secondary winding of the transformer is connected to the ground terminal of the inverter device. To be connected.

With the above configuration, the present invention has the same effect as the above item (1), and also allows a high-frequency earth current from a neutral point to flow to the earth terminal side of the inverter device. Becomes

(5) Further, according to the present invention, an insulating material is interposed between the inverter device housing and the conductive floor or structure, and the neutral point of the secondary winding of the transformer is set to the neutral point. A structure may be used in which the high-frequency current limiting element is connected to the ground terminal of the inverter device, and the high-frequency current limiting element is connected in series to the ground terminal of the inverter device housing.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing one embodiment of a grounding structure of an inverter system according to the present invention. Note that the same reference numerals in FIG. 4 denote the same parts as in FIG.

In this embodiment, similarly to the conventional example, an inverter device housing 2 containing an inverter device 1 and a motor housing 4 containing a motor 3 to be controlled are installed on a floor 5. And an electric motor 4 in the housing 4 are connected by a cable 6. The floor 5 may be made of concrete or other conventional general material, but is made of a conductive structure such as a steel frame of a building, a steel plate structure in a ship or a vehicle, or a metal housing as described above. In some cases. The inverter device 1 includes a rectifier 11, a filter circuit 12, an inverter circuit 13 including a switching element, and the like. The electric motor 3 includes a motor stator winding 3 which is a component of the electric motor.
1 is provided.

One grounding example of the inverter system is that, as in the prior art, a certain location of each of the housings 2 and 4 is used as ground terminals 1E and 2E, and the ground terminals 1E and 2E are individually connected to ground wires 14 and 32, respectively. And are connected to the ground poles 15 and 33 of the floor 5, respectively.

The grounding structure according to the present invention is particularly different from the conventional one in that the inverter housing 2 and the floor 5
Insulating material 41 is interposed between the first and second floors to insulate the inverter housing 2 from the floor 5 so that no ground current flows through the floor 5.

Further, for example, an inductance 42 as a high-frequency current limiting element is inserted in series with the ground wire 14 connecting the ground terminal 1E of the inverter device housing 2 and the ground pole 15, and high-speed switching by the switching element of the inverter circuit 13 is performed. The generated high-frequency earth current is suppressed.

In addition, in the grounding structure of the system of the present invention, the inverter device housing 2 and the motor housing 4 are connected by a low impedance ground wire 43, and the inverter circuit 13 and the motor stator winding 31 are connected. When the cable 6 to be connected is provided with a conductive shield 6a, the conductive shield 6a is connected to the ground terminals 1E, 2
E, so that no stray capacitance is generated between the output of the inverter device and the floor 5.

Next, the operation in the case where the above-described ground structure of the inverter system is employed will be described. now,
When switching control is performed on the switching element of the inverter circuit 13, a stray capacitance Cs exists between the motor stator winding 31 and the motor housing 4, and this stray capacitance charges and discharges, as described in the conventional example. Ground current is flows on the floor. This is the same in the inverter device 1, and the circuit including the rectifier 11, the filter circuit 12, and the inverter circuit 13 and the inverter device housing 2
As described above, the stray capacitance Ci exists between the two, and the ground current is flows through the stray capacitance Ci and returns to the inverter circuit 13.

Therefore, as described above, while the earth current is flows due to the existence of the stray capacitance, it is also difficult to artificially determine the path of the earth current. If the inverter device 1 is insulated from the floor 5 by interposing the insulating material 41 between the inverter 5 and the ground 5, it is possible to prevent the ground current is from flowing to the floor 5. However, it is not preferable from the viewpoint of safety to completely insulate the inverter device 1 from the floor. The reason is that, in the case of the inverter device housing 2 that can be easily touched by an operator or the like, it is obliged that the inverter device housing 2 be directly connected to a ground electrode via a ground wire from the viewpoint of human safety. .

Therefore, the grounding structure according to the system of the present invention further includes a grounding terminal 1E of the inverter housing 2.
If the inductance 42 is inserted in series with the ground wire 14 connecting the ground electrode 15 and the ground electrode 15, the high-frequency ground current is suppressed, and the DC potential of the inverter device housing 2 can be maintained at the same level as the ground electrode 15. It becomes possible.

However, since the path through which the ground current is flows does not exist except for the ground line 14, the inverter circuit 13
Since the common mode potential generated when the switching element is turned on and off is applied to both ends of the inductance 42, the potential of the inverter device housing 2 may fluctuate.

Therefore, in order to suppress the potential fluctuation of the inverter device housing 2, if the inverter device housing 2 and the motor housing 4 are directly connected by the low impedance ground wire 43, the potential fluctuation can be suppressed. . That is, since the ground current is flows through the ground wire 43 without flowing into the ground poles 15 and 33, no potential difference occurs between both ends of the inductance 42, and the potential of the inverter housing 2 is stabilized.

Therefore, according to the above-described embodiment, by inserting the inductance 42 in series with the ground wire 14 from the inverter device housing 2 to the ground electrode 15, it is generated by high-speed switching of the inverter circuit 13. The high-frequency earth current is suppressed, and the DC potentials of the inverter housing 2 and the ground electrode 15 can be maintained at the same level.

Further, an insulating material 41 is interposed between the inverter device housing 2 and the floor, and
Is connected to the motor housing 4 with a low impedance ground wire 43, a high-frequency ground current flows through the low impedance ground wire 43, so that the potential of the inverter device housing 2 can be stabilized. 1 can contribute to stable operation.

When the cable 6 for supplying the output of the inverter circuit 13 to the motor 3 is provided with a conductive shield 6a, the shield 6a is connected to the ground terminals 1E and 2E of the casings 2 and 4. Thereby, the stray capacitance between the cable 6 and the floor 5 is eliminated, which contributes to the stable operation of the entire system.

(Other Embodiments) (1) FIG. 2 is a configuration diagram illustrating another embodiment of the grounding structure of the inverter system according to the present invention. In this figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description is left to the description of FIG. 1. Here, particularly different parts will be described.

The grounding structure of this inverter system includes a low-frequency current limiting element such as a capacitor between the ground terminal 1E of the inverter housing 2 and the low-impedance ground wire 43 in addition to the components shown in FIG. 44 is inserted.

The reason for adopting the above structure is as follows. That is, the high-frequency earth current flows through the ground wire 43 connecting the inverter device housing 2 and the motor housing 4 as described above, but the ground wire 43 and the ground pole 15 are connected to the inverter device housing 2. Ground wire 14 leading to
Form a loop, so that it is likely to be induced from the surroundings. In particular, an induced current having an operating frequency component of the inverter circuit 13 may flow due to the influence from the output-side cable 6 of the inverter circuit 13.

Therefore, by inserting a capacitor 44 between the ground terminal 1E of the inverter device housing 2 and the low impedance ground line 43, this capacitor 44
As a result, harmful low-frequency current is suppressed or cut off, and high-frequency ground current is allowed to flow through the ground line 43 without restriction. Thereby, it is possible to make the configuration hard to receive guidance from the surroundings.

(2) FIG. 3 is a configuration diagram illustrating still another embodiment of the grounding structure of the inverter system according to the present invention. Also in this grounding structure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description is left to the description of FIG. 1. Here, particularly different parts will be described.

This embodiment is an application example in which the power supply of the inverter device 1 is applied to a non-grounded system in FIGS. 1 and 2, but an example for explaining improvement of grounding for a power supply grounding system. It is. In the figure, reference numeral 51 denotes a transformer for supplying power to the inverter device 1, and reference numeral 52 denotes a ground electrode of a secondary circuit of the transformer. An earth wire 53 is connected between the transformer 51 and the ground electrode 52. . A ground wire 55 is similarly connected between the shield of the transformer 51 and another ground electrode 54.

Further, a ground wire 56 is connected from the ground terminal 51E of the transformer 51 to the ground terminal 1E of the inverter device housing 2.

Next, the operation when the above-described grounding structure is used will be described.

In general, in the case of a power supply grounding system, a large ground current flows in the grounding system, and it is easy for a peripheral device to be damaged. Therefore, in such a power supply grounding system, it is general that the neutral point of the secondary winding of the transformer 51 is grounded. As a result, a high-frequency ground current flows through the ground wire 53 as a result. In addition, there is a problem that earth current flows through the floor 5 and the building structure.

To prevent ground current from flowing through the floor 5 and the building structure, a ground wire is connected between the ground terminal 51E, which is the neutral point of the transformer 51, and the ground terminal 1E of the inverter housing 2. 56 and the ground wire 5
By flowing a high-frequency earth current through 6, it is possible to prevent the high-frequency earth current from flowing through floor 5, building structure, and ground electrode 52.

(3) In the above embodiment, the insulating material 41 is interposed only between the inverter device housing 2 and the floor 5. A structure in which an insulating material is interposed may be used. Further, the low impedance ground wire 43 does not necessarily need to be a wire, but may be a conductive member.

In addition, the present invention is not limited to the above-described embodiment, and can be variously modified and implemented without departing from the gist thereof. Further, the embodiments can be implemented in combination as much as possible, and in that case, the effect of the combination can be obtained. Furthermore, each of the above embodiments includes various upper and lower stage inventions, and various inventions can be extracted by appropriately combining a plurality of disclosed components. For example, when an invention is extracted by being able to omit some of the constituent elements from all the constituent elements described in the embodiment, when implementing the extracted invention, the omitted part may be omitted by a well-known common technique. It is supplemented.

[0048]

As described above, according to the present invention, even when it is mounted on a conductive floor or structure, the flow of earth current to these floors or the like can be restricted, and the failure of peripheral equipment can be prevented. Can be.

Further, according to the present invention, the stable operation of the inverter device and the safety of personnel and structures can be ensured by cutting off the high-frequency earth current or limiting the low-frequency current.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of a grounding structure of an inverter system according to the present invention.

FIG. 2 is a diagram illustrating another embodiment of the grounding structure of the inverter system according to the present invention.

FIG. 3 is a diagram illustrating still another embodiment of the grounding structure of the inverter system according to the present invention.

FIG. 4 is a diagram illustrating a grounding structure of a conventional inverter system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inverter apparatus 1E, 2E ... Ground terminal 2 ... Inverter apparatus housing 3 ... Electric motor 4 ... Electric motor housing 5 ... Structure including a floor 6 ... Cable 11 ... Rectifier 12 ... Filter circuit 13 ... Inverter circuit 14, 32, 53 , 55 ... ground wire 15, 33, 52, 54 ... ground pole 31 ... motor stator winding 41 ... insulating material 42 ... inductance 43 ... low impedance ground wire 44 ... capacitor 51E ... ground terminal 56 ... ground wire

Claims (6)

[Claims] An inverter system in which an inverter device housing including an inverter device including a switching element and a motor housing driven by an output of the inverter device are installed on a conductive floor or a structure. , Wherein an insulating material is interposed between the inverter device housing and the conductive floor or structure, and a high-frequency current limiting element is connected in series to a ground terminal of the inverter device housing and grounded. The grounding structure of the inverter system. 2. An inverter system in which an inverter device housing including an inverter device including switching elements and a motor housing driven by an output of the inverter device are installed on a conductive floor or structure. In the above, an insulating material is interposed between the inverter device housing and the conductive floor or structure, and ground terminals of the inverter device housing and the motor housing are connected to each other by a conductive member, A grounding structure for an inverter system, wherein a high-frequency current limiting element is connected in series to a ground terminal of the inverter device housing and grounded. 3. An inverter system in which an inverter device housing including an inverter device including a switching element and a motor housing driven by an output of the inverter device are installed on a conductive floor or structure. An insulating material is interposed between the inverter device housing and the conductive floor or structure, and a conductive member is provided between a ground terminal of the inverter device housing and a ground terminal of the motor housing. And a low-frequency current limiting element connected in series, and a high-frequency element limiting element connected in series to the ground terminal of the inverter device housing and grounded. 4. The inverter device, wherein an inverter device housing including an inverter device including a switching element and a motor housing driven by an output of the inverter device are installed on a conductive floor or structure. An inverter system in which a neutral point of a transformer constituting a power supply for supplying power to the ground is grounded, wherein an insulating material is interposed between the inverter device housing and the conductive floor or structure, and An inverter system, wherein a high-frequency current limiting element is connected in series to a ground terminal of an inverter device housing and grounded, and a neutral point of a secondary winding of the transformer is connected to a ground terminal of the inverter device. Grounding structure. 5. The inverter device according to claim 1, wherein an inverter device housing including an inverter device including a switching element and a motor housing driven by an output of the inverter device are installed on a conductive floor or structure. An inverter system in which a neutral point of a transformer constituting a power supply for supplying power to the ground is grounded, wherein an insulating material is interposed between the inverter device housing and the conductive floor or structure, and An inverter, wherein a neutral point of a secondary winding of a transformer is connected to a ground terminal of the inverter device, and a high-frequency current limiting element is connected in series to a ground terminal of the housing of the inverter device and grounded. System grounding structure. 6. The grounding structure for an inverter system according to claim 1, wherein a conductive shield is applied to a cable connecting the inverter device and the electric motor. A grounding structure for an inverter system, wherein a conductive member is connected to a ground terminal of each of the housings.