JP2567495B2 - Inverter device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device, and more particularly, to a seed layer between conductors between a smoothing capacitor of a DC power source and a switching element of each phase bridge-connected. The present invention relates to a voltage source inverter device connected by parallel conductors having a structure.

[Conventional technology]

FIG. 11 shows the connection structure of the voltage type inverter shown in, for example, Japanese Patent Laid-Open No. 620069/1987. As shown in this figure, the smoothing capacitor (1) and each switching element (4) connected in a bridge, which is the main body of the inverter circuit, are connected.
(7) is connected by the parallel conductor (2) to form a so-called parallel conductor circuit of an inverter. In the figure, (3) is a current detector for detecting a DC bus current, (8) to (11) are connected in parallel to the switching elements (4) to (7), respectively, and commutation energy when the inductive load of the inverter is cut off. Is a free-wheeling diode for returning the current to the DC power source, and (12) is an output terminal for outputting the AC output which is the conversion output from each of the switching elements (4) to (7) to the outside.

The parallel conductor (2) described here refers to a wiring conductor in which a pair of conductors having a plate-like shape and a rectangular cross section are laminated via an insulator. The parallel conductors have the characteristic that the effective inductance is extremely small and the capacitance therebetween is large. Generally the capacitance is (S is the area of the plate conductor, ε is the dielectric constant of the insulator, and 1 is the distance between the conductors). Therefore, in a structure such as this parallel conductor, S is large and l is small, so C is very small. In addition, the current detector (3) has switching elements (4) to
In order to directly detect the current of (7), it is inserted and connected between the parallel conductor (2) and the switching elements (4) to (7). Further, as the detection accuracy of the current detector (3), since the current at the time of short circuit is very large, coarse accuracy is sufficient.

FIG. 12 shows that when the output terminal (12) is short-circuited while the switching elements (4) and (7) are on, the current detector (3) detects an overcurrent, and the switching elements (4),
Turn off (7). It is a figure for demonstrating what kind of voltage is applied to the output of a switching element (4) at this time.

Since the parallel conductor (2) has a small inductance component and a large capacitive component, the capacitance between the conductors is equivalently the capacitance (C _s ).
In addition, the current detector (3) has some inductance for detecting the current value by using the magnetic field generated by the current. Therefore, it is represented by the inductance L ₁ (14).

Now, when the output terminals (12) are mistakenly short-circuited while the switching elements (4) and (7) are turned on, an excessive current flows, which is detected by the current detector (3) and the switching elements ( 4) and (7) are also turned off.

Now, when the switching elements (4) and (7) are turned off, the output line is somewhat inductive, so that the current I _O is kept flowing. Therefore, the free wheeling diodes (10) and (9) are turned on. On the other hand, the DC bus current is cut off, An induced voltage represented by is generated.

Therefore, the voltage V _CE related to the output of the switching element (4) which has just been turned off is represented by V _CE = V _DC + V _L. (Now, the ON voltage of the free wheeling diode (10) is smaller than others, so it is set to 0.) L _L is proportional to the product of L ₁ and di _D / d _t , so when a large current is cut off instantaneously, etc. A particularly large voltage V _L is generated.

In the above example, the current detector (3) is used to detect the DC bus current flowing between the smoothing capacitor (1) and each switching element (4) to (7), but as shown in FIG. Is separated from the P-side conductor 1 (21a) and the P-side conductor 2 (21b) by making a predetermined gap, and a resistor (24) for current detection is arranged in the gap, and the voltage between the resistors (24) is The DC bus current may be detected based on the above. In the figure, (1) is a smoothing capacitor that is a main circuit capacitor, (21a) and (21b) are P-side conductors 1 and 2, (22) is an N-side conductor, and (23) is a P-side and N-side conductor. An insulating plate for insulation, (24) is a resistor for current detection, and is a connection wire (26) to the resistance connection terminals (25) and (25) of the P-side conductor 1 (21a) and P-side conductor 2 (21b). Connected by. (27) is a current detection circuit, and (28) is a main circuit element composed of each switching element.

The operation of this circuit, the voltage at both ends represented by V = I _D · R (R value sense resistor) of the resistors (24) occurs, the current detected by measuring the V Circuits (27)
The value of I _D can be measured with.

Next, FIG. 13 is a diagram equivalently showing each wiring inductance in the inverter parallel conductor circuit. In the figure, the same reference numerals as those in FIG. 12 indicate the same or corresponding portions. In the figure, L ₁ (17) to L ₆ (22) are wiring inductances,
L _7a (12a) to L _7c (12c) indicate the wiring inductance of the output line (12).

Fig. 14 shows the current path during output short circuit and the induced voltage V ₁ (20) to V ₆ (25) induced in the wiring inductance from L ₁ (17) to L ₆ (22) when the current is cut off. FIG.

For example, when the output line (12) of the inverter is erroneously short-circuited, the switching element (13) W ⁺ , the switching element (6) U ⁻ , and the switching element (7) V ⁻ ON signal (others are OFF signals) are input. Then, the current flows from the switching element (13) W ⁺ through the switching element (6) U ⁻ and the switching element (11) V ⁻ as shown in the figure. At this time, if this current is cut off, L ₁ (17) to L ₆ (2
Inductive voltage V ₁ (20) to V ₆ due to the inductance up to 2)
(25) occurs. The magnitude can be expressed by the product of the ratio of the breaking current per unit time and the inductance.

When the output is short-circuited, a very large current flows, and unless it is cut off suddenly, the output element will be destroyed and di / dt will become a very large value. Therefore, even if there is a slight wiring inductance, the induced voltage has a large value and is applied to the interrupted element, which may exceed the withstand voltage of the element. In FIG. 14, the voltage applied to V _CE of the switching element (13) W ⁺ is V _CEW ⁺ = V _DC + V ₁ + V ₂ + V
It becomes ₃ + V ₅ + V ₆ .

In order to eliminate such adverse effects of wiring inductance, conventionally, as shown in Fig. 18, a plate-shaped conductor having a rectangular cross section is laminated between wirings with an insulator interposed between them, and a structure is adopted in which the generated magnetic flux is canceled by each other. Was there.

 Hereinafter, this principle will be described with reference to FIG.

In FIG. 17, for example, a parallel conductor circuit is indicated by a broken line AA ′.
If the current flowing through each line is taken into consideration including its direction, the sum of the currents becomes 0. Therefore, the magnetic fields H = nI (I is the magnitude of the current, n is the number of turns in this case, 1) generated in the AA 'portion cancel each other out.

H becomes 0 means that magnetic flux φ = BS = μHS (B is magnetic flux density, S is cross-sectional area, μ is magnetic permeability)
Is 0. The surge voltage generated when the current is cut off is If they are arranged so that the magnetic fluxes cancel each other out, the surge voltage will be eliminated.

In FIG. 17, the portions where the sum of the currents becomes 0 are the circles, triangles, and squares.

Therefore, the circuit may be wired so as to cancel the magnetic flux generated in this portion.

FIG. 18 shows that, based on the above-mentioned principle, plate-shaped conductors having a rectangular cross section are laminated by interposing an insulator between the circles, triangles, and squares, and the generated magnetic fluxes are arranged so as to cancel each other.

By configuring the parallel conductor circuit as described above, it is possible to reduce the surge voltage that occurs when a large current is suddenly cut off as when protecting an output short circuit.
The switching element can be protected.

[Problems to be Solved by the Invention]

Since the conventional inverter device is configured as described above, the inductance of the current detector (1
Since the induced voltage due to 4) is directly applied to the switching element, there was a problem that the element was destroyed. Especially when an excessive current is flowing, such as during a short-circuit accident, it is necessary to shut off the switching element in a short time so as not to destroy it. Therefore, the induced voltage due to the inductance (14) of the current detector Became very large and there was a particular problem.

Also, in a case where a resistor (24) is connected between the P-side conductors 1 and 2 and a DC bus current is detected based on the voltage between the resistors, a parallel conductor circuit is used for the DC bus to connect this portion. Although the wiring inductance is lowered, the + side (P side) of the parallel conductor is divided in the middle to insert the detection resistance and is connected by the connecting line. Therefore, as shown in Fig. 16, the inductance of the detection resistor itself (24 _L1 ) and connecting line inductance (24 _L2 ) occur.

Therefore, when the overcurrent is cut off, There is a risk that the induced voltage represented by will be applied to the main circuit element and destroy the element. Further, since the detection resistor generates heat of I _D ² · R, the size of the detection resistor is increased and the inductance of the detection resistor itself is further increased.

In addition, regardless of the influence of the induced voltage due to the inductance component of the current detector or the resistor, a laminate bar is provided between the wirings to eliminate the adverse effect of the wiring inductance, and the magnetic fields generated in the wirings cancel each other. However, as can be seen from Fig. 18, since there are four layers between the V phase and W phase of the three-phase output, the leakage flux increases due to the distance between the two outer layers, and the effect of canceling the magnetic flux decreases. , The wiring inductance increases and the effect of the laminate bar decreases. In addition, the use of four layers increases the number of conductor plates and insulating plates as compared with the number of layers of three, so that there is a problem that the material cost, the work cost for mounting, and the like increase.

The first aspect of the present invention has been made to solve the above problems, and an object thereof is to obtain an inverter device capable of preventing a voltage generated by an inductance of a current detector from being applied to a switching element. Second
And the third invention aims to obtain an inverter device capable of reducing the inductance of the resistor even if a resistor for current detection is inserted in the DC bus.
An object of the fourth invention is to obtain an inverter device using an inverter parallel conductor circuit capable of forming a laminate bar in a three-layer structure.

[Means for solving the problem]

In the inverter device according to the first aspect of the present invention, a pair of DC input conductors from the smoothing capacitor of the DC power source to the switching elements of each phase connected in the three-phase bridge and an AC output conductor of each switching element are provided with an insulator interposed therebetween. As a laminated structure, a capacitance component is provided to the pair of DC input conductors, and an electric component for detecting a current flowing in the switching element is inserted between the DC input conductor having the capacitive component and the smoothing capacitor. .

The second invention is a laminated structure in which a pair of DC input conductors from a smoothing capacitor of a DC power source to a switching element of each phase connected in a three-phase bridge and an AC output conductor of each switching element are laminated with an insulator interposed therebetween. A part of the current path of at least one conductor among the plurality of conductors having the laminated structure is constituted by a resistor, and the current value is detected from the voltage across the resistor.

The third aspect of the present invention is obtained by bending the resistor according to the second aspect of the invention by folding back the low antibody in the direction perpendicular to the conductor.

Further, the fourth invention is such that a switching element is connected in series between a positive side DC input conductor and a negative side DC input conductor which are respectively connected to the positive side terminal and the negative side terminal of the smoothing capacitor of the DC power supply. Three configured arms are connected in parallel in the order of U-phase, V-phase, and W-phase to form a three-phase bridge, and the positive side and the negative side between the U-phase and V-phase switching elements that form this three-phase bridge. The side DC input conductor and the AC output conductor of the U-phase switching element are wired using means for canceling the magnetic field generated by the current flowing through each conductor, and the positive and negative sides between the V-phase and W-phase switching elements are arranged. The DC input conductor and the AC output conductor of the W-phase switching element are wired using a means for canceling the magnetic field generated by the current flowing through each conductor, and the U-phase and W-phase AC output conductors are connected to the V-phase. Min. To the AC output conductor for each The body together is obtained by a configuration to bring out to the outside.

[Action]

According to the first aspect of the present invention, by laminating an insulating material between a pair of DC input conductors, the DC input conductor is provided with a capacitive component, and the DC input conductor having the capacitive component and the above-mentioned smoothing are provided. Since an electrical detector that detects the current flowing through the switching element is connected between the capacitors, even if an induced voltage is generated by the reactance component of the current detector when the switching element is turned on, this induced voltage is generated between parallel conductors. Since it is absorbed by the existing capacitance, it is possible to prevent a surge voltage from being generated in the switching element.

Further, according to the second aspect of the present invention, since a part of the parallel conductor is formed of a plate-shaped resistor having a predetermined resistance value, the current detection resistor can be inserted in the DC bus without breaking the parallel conductor structure. Therefore, a low-inductance DC bus circuit can be constructed.

Further, according to the third aspect of the invention, the resistor according to the second aspect of the invention has a structure in which the magnetic fields generated by the current flowing through the resistor cancel each other out, so that a low-inductance DC bus circuit can be constructed.

According to the fourth aspect of the invention, the currents flowing through the respective conductors of the positive and negative side DC input conductors between the U-phase and V-phase switching elements and the AC output conductors of the U-phase switching elements which form the three-phase bridge. Are wired by using a means for canceling the magnetic field generated by, and the positive and negative side DC input conductors between the V-phase and W-phase switching elements and the AC output conductors of the W-phase switching elements are changed by the currents flowing through the conductors. Wiring is performed using a means for canceling the generated magnetic field, and each of the U-phase and W-phase AC output conductors is brought close to the V-phase AC output conductor to bring out the respective conductors to the outside. In addition to canceling out the magnetic flux, the parallel conductors can have a three-layer structure and the wiring inductance can be reduced.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an inverter parallel conductor circuit which constitutes the inverter device according to the present embodiment. The difference from the conventional FIG. 5 is that the current detector (3) is inserted between the smoothing capacitor (1) and the parallel conductor (2).

FIG. 2 is a diagram for explaining the current interruption at the time of output short-circuit, particularly the voltage shared by the switching elements in the inverter parallel conductor circuit in the present embodiment.

As in the conventional example, when the output terminals (12) are short-circuited while the switching elements (4) and (7) are on, the current detector (3) detects an overcurrent, and the switching elements (4), Turn off (7). At this time, when the free wheeling diodes (10) and (9) are turned on, the inductance L ₁ (14) of the current detector (3) causes The induced voltage V _L is generated, but this time the induced voltage is absorbed by the capacity (C _S ) because of the parallel conductor capacity (C _S ). Therefore, the voltage applied to the switching element is V _CE
≈V _DC , so that a large voltage is not applied to the switching element unlike the conventional device.

In the above embodiment, the case of two arms (two pairs of switching elements) has been described, but the same effect can be obtained with a three-arm or multiple-arm inverter.

In the embodiment of the first invention, an example in which the DC bus current flowing in the parallel conductors is detected by the current detector has been shown.
As in the second aspect of the invention, even if a part of the P-side parallel conductor in the parallel conductor is formed by a resistor and the DC bus current is detected based on the detection voltage between the resistors, the same effect can be obtained. Play. FIG. 3 is a block diagram of a parallel conductor used in an embodiment of the second invention. In the figure, the same parts as those in FIG. 15 indicate the same or corresponding parts, and detailed description thereof will be omitted.

In the figure, (24a) is a detection resistor portion (plate) having a predetermined resistance value, and (25a) is a voltage detection terminal for measuring a voltage drop value generated in the detection resistor portion (24a).

As is clear from FIG. 3, since the parallel conductor structure is not broken in order to put the detection resistance, a low inductance is realized. In addition, since it has a plate shape and can have a relatively large surface area, there is an advantage that the Joule heat generated by I _D ² · R can be efficiently dissipated.

In the present embodiment, the detection resistor portion is composed of a metal plate,
The same effect can be obtained by applying a resistance paste or the like.

FIG. 4 is a side view of the parallel conductor of this embodiment, FIG. 5 is an inverter device using the parallel conductor of this embodiment, and FIG. 6 is an equivalent circuit thereof, as shown in this equivalent circuit. Since the DC bus has a very small inductance, even if a large current is suddenly cut off, Since the surge voltage due to is small, the main circuit element (28) is not destroyed unlike the conventional case.

FIG. 7 is a diagram showing an embodiment of the third invention, and FIG. 4 is an explanatory diagram thereof. As can be seen from FIG. 7, since the detection resistor portion has a structure in which it is folded back in the middle, the generated magnetic fields cancel each other out, so that low inductance is realized.

FIG. 9 is a diagram showing the principle of an embodiment of the fourth invention,
FIG. 10 is a diagram showing an example of wiring of the device of this embodiment.

FIG. 9 differs from the conventional FIG. 18 in how to take out the output lines of the U, V and W phases. It suffices that the sum of the currents, including the direction, becomes 0. Therefore, as shown in FIG. 9, the U and W phase output lines are taken out from the V phase position.

 In this case, the sum of the currents in the circles, triangles, and circles is zero.

FIG. 10 shows that the circles, triangles, and circles are made of parallel conductors such as laminate bars based on the principle of FIG.

As can be seen from comparison with FIG. 18, there are no four layers, and there are at most three layers, and there is a magnetic flux canceling effect (because of the three-layer structure, leakage flux is reduced, There is a magnetic flux offset effect above).

In addition, in the above-mentioned embodiment, in order to cancel the magnetic flux, the laminate bar in which the conductor plates having the rectangular cross section are laminated via the insulating plate is used. You may use.

(Effect of the Invention) As described above, according to the first invention, the electric component having the inductance component is provided between the parallel conductor of the DC bus and the smoothing capacitor. There is no longer a burden on the switching element side. Therefore, even when a high surge voltage such as an overcurrent cutoff is generated, the switching element can be protected without being destroyed, so that a highly reliable device can be obtained.

Further, according to the second aspect of the invention, since the resistor for detecting the current is provided in the parallel conductor without breaking the parallel conductor structure,
A circuit with a small inductance of the DC bus was obtained.

Therefore, even if the large current is suddenly cut off, the generated surge voltage becomes small. Further, since the surface area of the detection resistor portion is increased, the heat radiation effect is also increased.

According to the third aspect of the invention, since the resistors according to the second aspect of the invention are folded back and bent in the vertical direction with respect to the parallel conductors, the generated magnetic fields cancel each other, so that a low inductance of the parallel conductors is realized. There is an effect that can be done.

Further, according to the fourth aspect of the invention, the main circuit portion of the inverter is connected so that the portions where the sum of the currents becomes 0 are connected by a low inductance conductor such as a laminate bar so as to have a three-layer structure at the maximum. Since the phase distance is shortened and the leakage magnetic flux is reduced, the effect of canceling the magnetic flux is enhanced, and the wiring inductance is reduced, so that a high-performance inverter device with high coupling can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an inverter parallel conductor circuit which constitutes an inverter device according to an embodiment of the first invention, and FIG. 2 is a diagram for explaining voltage sharing during current interruption of the parallel conductor circuit according to this embodiment. FIG. 3 and FIG. 3 are configuration diagrams of parallel conductors in an inverter device according to an embodiment of the second invention,
FIG. 4 is a side view of the parallel conductor in this embodiment, FIG. 5 is a configuration diagram of an inverter device using the parallel conductor in this embodiment, FIG. 6 is an equivalent circuit diagram of the inverter device in this embodiment, and FIG. FIG. 8 is a configuration diagram of parallel conductors in an inverter device according to one embodiment of the third invention, FIG. 8 is a diagram for explaining the operation of the parallel conductors in this embodiment, and FIG. 9 is one embodiment of the fourth invention. FIG. 10 is a diagram showing the principle of an inverter device according to an example, FIG. 10 is a wiring diagram of the device of this embodiment, FIG. 11 and FIG.
FIG. 12 is a circuit diagram of an inverter parallel conductor circuit in a conventional device, FIG. 12 is a diagram for explaining voltage sharing at the time of current interruption of a parallel conductor circuit in a conventional device, and FIG. 13 is an equivalent view of each wiring reactance. Inverter main circuit diagram, 14th
The figure shows the situation when the output is short-circuited in the conventional device.
FIG. 17 is an equivalent circuit diagram of a conventional inverter device, FIG. 17 is a diagram showing the principle of a conventional inverter parallel conductor circuit, and FIG. 18 is a wiring diagram of the conventional inverter parallel conductor circuit. In the figure, (1) is a smoothing capacitor, (2) is a parallel conductor, (3) is a current detector, (4) to (7), (13),
(14) is a switching element, (12) is an output terminal, (21)
Is a P-side conductor, (22) is an N-side conductor, and (24a) and (24b) are detection resistor parts. The same reference numerals in the drawings indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-144578 (JP, A) JP-A-62-221878 (JP, A) JP-A-1-185172 (JP, A)

Claims (3)

(57) [Claims] 1. A pair of DC input conductors from a smoothing capacitor of a DC power source to a switching element of each phase connected in a three-phase bridge and an AC output conductor of each switching element as a laminated structure with an insulator interposed therebetween. 2. An inverter device characterized in that the DC input conductor is provided with a capacitive component, and an electrical component for detecting a current flowing through the switching element is inserted between the DC input conductor having the capacitive component and the smoothing capacitor. 2. A laminated structure between a pair of DC input conductors from a smoothing capacitor of a DC power supply to a switching element of each phase connected in a three-phase bridge and an AC output conductor of each switching element with an insulator interposed therebetween, An inverter device characterized in that a part of a current path of at least one conductor among a plurality of conductors having a laminated structure is constituted by a resistor, and a current value is detected from a voltage across the resistor. 3. The inverter device according to claim 2, wherein the resistor is bent and bent in a direction perpendicular to the conductor.