JPS62181680A - Inverter apparatus - Google Patents

Abstract

PURPOSE:To inhibit the rate-of-rise of accidental currents by inserting an inductor magnetically coupled with sections among arms, in which switching operation is paired, in series with switching elements for each arm. CONSTITUTION:Two pairs of inductors 5U, 5Y and 5V, 5X magnetically coupled with sections between transistors 4U and 4Y and with sections between 4V and 4X, in which switching operation is paired, differentially are each inserted in series with the transistors 4U, 4Y, 4V, 4X as the inhibiting means of the rate-of-rise of DC short-circuit currents. A current detector 7, an overcurrent detecting circuit 8 and a drive-signal blocking circuit 9 are mounted as overcurrent protective means.

Description

Detailed Description of the Invention (Objective of the Invention) (Industrial Field of Application) The present invention relates to overcurrent protection for voltage source type inverter devices, and in particular to an inverter that suppresses DC short-circuit current using magnetically coupled inductors. Regarding equipment.

(Prior Art) FIG. 5 shows an example of the circuit configuration of a voltage source type inverter device according to the prior art. In the figure, 1 is a DC power supply, 2 (J,
Load, 3 is wiring inductance, 4u, 4v, 4x,
4v are transistors for the U arm, V arm, X arm, and Y arm, respectively; 7 is a current detector that detects the current in the DC section; 8 is an overcurrent detection circuit; 9 is the transistor 4u.
A base blocking signal that gives a blocking command for the base drive signal of ~4Y, 10 is a switching control circuit, IIUY,
IIVX is a base drive circuit that drives the transistors of the U-Y arm and the V-X arm, respectively.

Various switching methods have been proposed for the above-mentioned inverter circuit example, but since they are not the subject of the present invention, the following example will be used for detailed explanation. First, when the transistors 4u and 4Y are conducting, the current flows from the DC power supply 1 to the inductance 3 of the wiring shown together, to the transistor 4u,
The current flows through a path passing through the load 2, the l-transistor 4Y, and the current detector 7.

Next, block the conductive transistors 1 to 4U and 4Y to 1F.
Switching of transistors A) Transistors 4v and 4x@ become conductive after a certain period of time to ensure time. At this time, the current flows from the DC power supply 1 to the wiring inductance 3, to the transistor 4ν, to the load 2, to the transistor 4.
x, flows along a path passing through the current detector 7. Above operation 81
AC power is supplied from the DC power supply 1 to the load 2 by repeating the cycle as a recycle. The important thing here is that
Any switching method, dust arm and X arm 1 to transistor 4u, 'lx or ■ arm and Y
There must be no period during which the arm transistors 4V and 4Y are conductive to +15.

If the above-mentioned conduction period were to occur, an excessive current would flow through the wiring inductance 3 and the collector-emitter impedance of two transistors, making it impossible to supply power to the load 2. In the inverter device described above, the inductance of the wiring is generally designed to be as small as possible in order to reduce the surge voltage during switching off, and the saturation impedance between the collector emitter of 1 and the transistor is also very small. The excessive current (hereinafter referred to as DC 710 circuit current) has a very large rate of increase and becomes a large current, which usually destroys the transistor.

Now, as a method of protecting 1 to 1 to 2 Lancistors from the above-mentioned DC short circuit current according to the prior art, there is shown in FIG.
, a current detector 7 is inserted in the direct current short path, and the overcurrent detection circuit 8 is further protected, so that when a current exceeding a predetermined value flows (J), a base blocking signal 9 is immediately output and the ~
It is common and rare to block the base of a transistor.

(Problem to be Solved by the Invention) However, the switching elements used in the inverter HVI are not limited to the transistors mentioned above, but various composite elements are being developed, and their switching speeds have been significantly increased. . In order to suppress the surge voltage associated with the current change rate 571, the inductance 3 of the circuit wiring has been made even smaller, and the overcurrent detection circuit 8 is actually used to prevent electrical malfunction of electronic circuits. It has a detection delay of 11) with a minimum filter. In other words, although the DC short-circuit current rate increases more and more, there is a limit to reducing the detection delay gate 4 (j), so the protection of the switching elements against DC short-circuit current is simply to step up the overcurrent detection circuit 8. In some cases, it is difficult to simply block the base of the switching element by using a method of blocking the base of the switching element, and this becomes a very important problem when using high-speed switching elements.

An object of the present invention is to provide an inverter device that easily and reliably protects against DC short circuit current.

(Structure of the Invention) (Means for Solving the Problems) As shown in FIG. 1-2 silk inductors 5U, 5Y and 5v differentially magnetically coupled between transistors 4U and 4Y and between J3 and /lv and 4x.

A current detector 7, an overcurrent detection circuit 8, and a drive signal blocking circuit 9 are provided as overcurrent protection means, and the above I・It improves the protection method for switching elements such as transistors.

(for production) In the above (j), there are two silk inductors 5u.

5Y, 5v, and 5x are differentially connected in series with respect to the current generated during normal switching operation, so they function as a much smaller vessel than their respective self-inductances, and the above-mentioned It has almost no effect on the load current.

On the other hand, if a period occurs in which transistors 1 to 4U and 4x or 4V and 4Y are both conductive, the fault current will pass through the two inductors 5U and 5x, or 5ν and 5Y, which are not magnetically coupled, in series. Because of this, the fault current is limited by the inductance 3 of the two inductors and the wiring. .

(Embodiments of the present invention) The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, a DC power supply 1 includes transistors 4u, IAv, /'lX, 4Y, inductors 5u, 5v, 5X, 5Y whose switching operations are magnetically coupled to each other in pairs, and a free-wheeling diode 6u. 6v
, 6X, and 6Y are converted into AC power via a single-phase bridge inverter, which constitutes a main circuit, and supplied to the load 2. Here, 3 collectively indicates the inductance of the circuit wiring. The transistor drive circuit transfers the signal from the switching control circuit 10 to the base drive circuit ti.
UV and 11VX are amplified and connected to each of the above transistors. The overcurrent protection circuit compares and judges the current signal detected by the current detector 7 with a predetermined setting value in the overcurrent detection circuit 8, and in the case of overcurrent, the base blocking signal 9 is sent to the switching control circuit 10. Give a command to stop.

Next, the operation will be explained using FIGS. 2 and 3.

FIG. 2 is an explanatory diagram showing an example of the main circuit operation of the present invention, and for the sake of simplicity, parts having the same functions as those in FIG. 1 are given the same reference numerals and referred to above. In the same figure,
1uy-p is U, Y arm transistor 4LJ, 4N
iUY-g is the current that flows through the load to the load, and iUY-g is the current that flows from the freewheeling diode from load 2 only in the case of an inductive load, at the moment when the transistors 'lu and 4Y of the U and Y arms become non-conductive. This is a regenerative current that flows to the DC power supply 1 through 6x and 6shi. J: 181 is transistor 4
The direct current that flows when U and 4x conduct at the same time) is the 0-circuit current. FIG. 3 is a current waveform diagram illustrating the difference in overcurrent protection between the prior art and the present invention. In the same figure, 181 is a DC short circuit current waveform when using the present invention;
1B2 is a DC short circuit current waveform when using the conventional technique. loc is a set value for overcurrent detection, and after a delay time to from the overcurrent detection time until the transistor starts switching off, the DC short-circuit current reaches maximum values l8P2 and Iarl, respectively.

The power current 1uv-p and the regenerative current 1uv-p shown in Fig. 2
As is clear from the path of u, the same current flows through the inductors (5υ and 5Y in the explanation of the same figure) whose switching operation is differentially magnetically coupled between the paired arms, and one The inductance of the circuit when viewed as an open circuit becomes very small. Now, the inductor 5
If the self-inductances of υ and 5V are made equal, the mutual inductance is M, and the wiring inductance @L is considered, the composite inductance Lo when considering the above closed circuit is given by Lo=21 2M + Lz, and the ideal If the degree of coupling (coupling coefficient is 1) is obtained, Lo=Lz. However, when a small DC yri circuit current ia1 flows, a closed circuit passes through the inductors 5U and 5x, which are not magnetically coupled to each other.
If the inductance of the closed circuit in this case is L6, then L6=21+l 1 . In other words, when the inverter device is operated with normal switching operation, the magnetically coupled inductor according to the present invention behaves as if it were not present, and acts to suppress the fault current increase rate only in the event of a DC short circuit. .

Now, as shown in FIG. 3, the same operation is performed between 04 and 1. )
Comparing the conventional overcurrent protection circuit with the present invention and the conventional overcurrent protection circuit, the fault current peak value in the present invention is much lower. This means that (υ current square time product of DC short circuit current (passing 12t)
becomes smaller, making it possible to protect the switching element from thermal energy damage in a short time range.

■ By suppressing the rate of increase in DC short-circuit current, it is possible to insert an appropriate filter into the overcurrent detection circuit so that the malfunction of the overcurrent detection circuit and the protection of the switching elements can be coordinated. Can be performed reliably and accurately.

As a result, things that could not be protected by conventional methods can now be protected by the present invention, and things where the protection circuit malfunctioned or was uncertain can now be done accurately and reliably.

FIG. 4 does not show other embodiments of the invention]1? This is a J composition diagram. In this embodiment, d3 is a free wheel diode 6u.

The connections of 6v, 6X, and 6Y are the same as in FIG. 1 and 51c, and the rest are the same configuration. The free wheel diode 6u.

6 * 6 x and 6 Y are connected at one end to the magnetically coupled inductor 5 u and J V T J x * J Y, but the other ends are connected through the wiring inductance 3 and current detector 7 respectively The configuration is such that it is directly connected to the DC power supply 1 without any need for a power source. Even with this configuration d3, it is possible to obtain exactly the same effects as in the first embodiment, and furthermore, it is possible to obtain an inverter device in which the surge voltage at the time of switching off is reduced.

In the above two embodiments, the switching elements have been described using transistors 1 to 1, but it goes without saying that the present invention is not limited to transistors 1 to 1 and is applicable to any self-extinguishing switching element.

〔Effect of the invention〕

According to the present invention, as explained above, when the inverter device is operated with normal switching operation,
Magnetically coupled inductors cancel each other out and behave as if they were not in the circuit, and when a DC short circuit occurs, the rate of increase in fault current is suppressed, making it easy and reliable to protect switching elements. It can be carried out.

As the speed of switching elements increases, it becomes more and more difficult to protect them, and the present invention is a simple method and is suitable for non-I;S.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an inverter device showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of the inverter circuit, and Fig. 3 is a diagram illustrating the operation of the present invention. A DC short circuit current waveform diagram for comparing and explaining the effects of the invention, FIG. 4 is a configuration diagram showing another embodiment of the invention, and FIG. 5 is a configuration diagram of an inverter device group according to the prior art.1 ...DC power supply, 2...Load, 3...Wiring inductance, 4u, 4v, 4x, 4y = transistor, 5u, 5y
...Magnetic coupling inductor, 5νt 5x...Magnetic coupling inductor, 6U, 6 Sea 6 x + 6 Y...
・Freewheeling diode, 7...Current detector, 8...
Overcurrent detection circuit, 9...Base blocking signal, 10...Switching control circuit, 11UY, 11νX...Base drive circuit, 1u
y-p...Current flowing through U-Y arm, 1uv-
R...Regenerative current flowing through the U-Y arm, is-+...
・DC short-circuit current according to the present invention, l5r1... Maximum value of DC short-circuit current according to the present invention, 182... DC short-circuit current when according to the prior art, l3F2... When according to the prior art Maximum value of DC short circuit current, Ioc: Overcurrent detection setting value, tD: Delay time from overcurrent detection time until the transistor starts switching off. Agent Patent Attorney Noriyuki Chika Yudo Hirofumi MitsumataFigure 1Figure 3vlJ Figure 4

Claims (1)

[Claims] An inverter device characterized in that an inductor magnetically coupled between arms of which switching operation is a pair is inserted in series with a switching element of each arm to suppress a rate of increase in fault current.