JPH09294377A - Inverter circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the prevention of two types of ringing phenomena by connecting two sets of series circuits each comprising a resistor and a capacitor having different constants to diodes. SOLUTION: In two sets of a snubber diode 11 and voltage clamp circuit diodes 19, 21, and a snubber diode 14 and voltage clamp circuit diodes 20, 22 series-connected, ringing phenomena occur at almost the same time as GTO1-4 are turned on and off. Therefore, series circuits comprising resistors R4 and capacitors G4 are connected with both the ends of the diodes 11, 19, 21 and diodes 14, 20, 22. In addition, series circuits comprising resistors R5 and capacitors C5 are connected with the snubber diodes 11, 14. This prevents ringing phenomena in each set of the three diodes (11, 19, 21), (14, 20, 22), and malfunctions of a gate circuit comprising GTO1-4.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an inverter circuit.

[0002]

2. Description of the Related Art GT is used for driving an induction motor of a rolling mill.
An O inverter is used. FIG. 6 is a main circuit configuration of a three-level inverter as an example of the inverter.
FIG. 7 is a circuit example of one phase of this inverter. 1 in the figure
~ 4 is GTO, 5-8 is a free wheel diode, 9,
10 is an anode reactor, 11-14 is a snubber diode, 15-18 is a snubber capacitor, 19-22 is a diode of a voltage clamp circuit, 23 and 24 are clamp diodes for three levels, 25-28 are voltage clamp circuit capacitors, 29 , 30 are power capacitors, 31, 32
Is a DC power supply, 33 and 34 are energy regeneration circuits, 35 is a resistor, and 36 is an output terminal.

A snubber circuit consisting of a diode and a capacitor is connected to each GTO to limit the waveform of the applied voltage and prevent destruction. When the energy stored in the snubber capacitors 15 to 18 is regenerated to the power supply, the efficiency of the inverter can be increased. In this circuit, the energy stored in the snubber capacitors 16 and 17 is consumed by the resistor 35, but the energy stored in the snubber capacitors 15 and 18 is regenerated to the power supply. Here, the energy regeneration operation will be described. When the GTO1 is turned on, the energy stored in the snubber capacitor 15 is stored in the diodes 19, 2
1, clamp capacitors 25, 27, power supply capacitor 2
9, the anode reactor 9, the clamp capacitors 25 and 27 charged to the DC power supply voltage in the path of the GTO1
Then, the voltage of the clamp capacitors 25 and 27 is made equal to or higher than the DC power supply voltage. Then, the transferred energy is regenerated by the energy regeneration circuit 33 to the power source.

Next, when the GTO 1 is turned off, the snubber capacitor 15 is charged to the DC power supply voltage, and the energy stored in the anode reactor 9 is stored in the snubber capacitor 15,
Moving on to clamp capacitors 25 and 27, capacitor 1
The voltage of 5, 25, 27 is set to be equal to or higher than the DC power supply voltage. Then, this transferred energy is similarly used for the energy regeneration circuit 33.
Regenerated by the power supply. The same applies to the stored energy regeneration operation on the GTO 4 side.

Next, the ringing phenomenon when the diode recovers will be described. When GTO1 is turned off, the above-described operation is performed, and a voltage charged to the DC power supply voltage or higher is applied to the snubber diode 11, for example, and a ringing phenomenon occurs when the diode 11 recovers. FIG. 8 shows the voltage / current waveform of the snubber diode 11 and the voltage waveform of the GTO 1. The ringing phenomenon in the figure occurs due to the recovery characteristic of the snubber diode 11, and is a vibration due to the junction capacitance of the snubber diode 11 and the inductance of the circuit including the anode reactor 9.
This ringing phenomenon may cause malfunction of the gate circuit of the GTO, which leads to destruction of the GTO. Therefore, it is necessary to connect a circuit that suppresses ringing.

Although the ringing phenomenon when the GTO 1 is turned off has been described, the ringing phenomenon of the snubber diode 11 may occur when the GTO 1 is turned on. When the GTO 1 is turned on while the charging current of the snubber capacitor 15 is flowing through the snubber diode 11, the ringing phenomenon occurs when the voltage of the snubber capacitor 15 is applied to the snubber diode 11 and the snubber diode 11 recovers. FIG. 9 is a voltage / current waveform of the snubber diode 11. The ringing phenomenon in the figure occurs due to the recovery characteristic of the snubber diode 11, and is a vibration due to the junction capacitance of the snubber diode 11 and the inductance of the snubber circuit. Therefore, the vibration frequency is higher than that of the ringing phenomenon described above. Since this ringing phenomenon also adversely affects the inverter operation, it is necessary to connect a circuit that suppresses ringing.

So far, the ringing phenomenon of the snubber diodes 11 and 14 connected to the snubber capacitors 15 and 18 for regenerating the stored energy to the power source has been described. A similar ringing phenomenon occurs in the snubber diodes 12 and 13 of the snubber circuit in which the energy stored in the snubber capacitor is consumed by the resistor 35, but the ringing is suppressed by the resistor 35. Although other explanations are omitted, since a similar ringing phenomenon may occur in the voltage clamp circuit diodes 19 to 22, it is necessary to connect a circuit that suppresses ringing. That is, in the inverter circuit of FIG. 4, it is necessary to connect a circuit for suppressing the ringing phenomenon to the snubber diodes 11, 14 and the voltage clamp circuit diodes 19-22.

FIG. 10 shows a conventional example of an inverter circuit to which a circuit for suppressing such a ringing phenomenon of a diode is connected. Suppressor circuits R1 and C1 including resistors and capacitors are connected to the snubber diodes 11 and 14 and the voltage clamp circuit diodes 19 to 22, respectively. Thus, each diode is connected to a series circuit of a resistor and a capacitor for suppressing the two types of ringing phenomenon in common. However, in this conventional example, since the vibration frequencies of the two types of ringing phenomena are significantly different, it is not possible to commonly suppress the two types of ringing phenomena, and a circuit for suppressing the ringing phenomenon of the diodes is provided individually for each diode. Therefore, there are problems that the number of parts is increased, which hinders the miniaturization of the inverter circuit and increases the power consumption due to the resistance of the suppression circuit.

[0009]

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an inverter circuit equipped with a ringing suppression circuit having a small number of parts, which can suppress two types of ringing phenomena.

[0010]

According to the present invention, since the ringing phenomenon is two kinds of vibrations due to the junction capacitance of the diode and the inductance of the circuit, it is necessary to individually connect the suppression circuits and suppress the ringing. In the embodiment of FIG. 7, attention is paid to the fact that three diodes are connected in series, and a means for connecting the three ringing suppression circuit parts common to the diodes is provided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 5 shows an embodiment of the present invention.
Ringing suppression circuits R2, C2 and R3, C3, which are composed of two systems of resistors and capacitors having different constants for respectively suppressing two types of ringing phenomena in each of the snubber diodes 11 and 14 and the voltage clamp circuit diodes 19 to 22.
Are connected. According to this embodiment, the ringing phenomenon can be suppressed. FIG. 11 shows an example of the voltage waveform of the diode when the ringing phenomenon is suppressed, but this can prevent malfunction of the gate circuit of the GTO. It should be noted that the same effect can be obtained even with a suppressing circuit using only a capacitor for the ringing phenomenon with a high vibration frequency.

FIG. 1 shows another embodiment of the present invention. The ringing phenomenon with respect to the snubber diode 11, the voltage clamp circuit diodes 19 and 21 and the snubber diode 14 and the voltage clamp circuit diodes 20 and 22 which are configured to be connected in series occurs at the same time when the GTO is turned on and turned off. So diode 1
A series circuit of a resistor R4 and a capacitor C4 is connected to both ends of each of the diodes 1, 19, 21 and the diodes 14, 20, 22. Moreover, for the snubber diodes 11 and 14, a series circuit of a resistor R5 and a capacitor C5 is connected.
As described above, the ringing phenomenon between the diodes connected in series occurs at almost the same time, but it is considered that the respective ringing phenomena have different magnitudes. FIG. 1 shows an embodiment of the present invention in this case, and a diode having a large ringing phenomenon, for example, snubber diodes 11 and 1 is used.
An individual resistor and capacitor are additionally connected to 4. In this case, the capacitance of R5 and C5 connected in parallel to the three diodes connected in series can be made small,
Although the number of parts will increase, the total capacity does not increase so much. As described above, the ringing phenomenon of each of the three diodes can be suppressed by the configuration of FIG. According to the present invention, the ringing suppression circuit can be configured with a relatively small number of parts, and it is possible to solve the problems that the miniaturization of the inverter circuit is hindered and the power consumption due to the resistance increases.

FIG. 2 shows another embodiment of the present invention. In FIG. 1, a diode having a large ringing phenomenon, for example, snubber diodes 11 and 14 are additionally connected with individual resistors and capacitors, but in FIG. 2, only the capacitor C5 is connected. As the damping resistance of the capacitor C5, the resistor R4 which is connected in a lump is used. According to the present invention, it is possible to configure a ringing suppression circuit in which the number of parts is further reduced. Although the additional circuit is connected only to the snubber diodes 11 and 14 in the embodiments of FIGS. 1 and 2, it is sufficient to connect all the necessary diodes.

3 and 4 show another embodiment of the present invention.
In FIG. 3, a ringing suppressing circuit which is composed of one system resistor R6 and capacitor C6 is connected. The constants of the resistor and the capacitor are selected so that the two ringing phenomena having different frequencies described above have a suppressing effect on the one having the more severe ringing phenomenon. In FIG. 4, a collective ringing suppressing circuit including two systems of resistors and capacitors R7, C7 and R8, C8 is connected. The constants of the resistor and the capacitor are selected so that the two types of ringing phenomena having different frequencies described above can be individually suppressed. As described above, also in the embodiments of FIGS. 3 and 4, the number of parts of the ringing suppression circuit can be reduced as compared with FIG. 10, and the problem that the miniaturization of the inverter circuit is hindered and the power consumption due to the resistance is increased. Can be solved. In the above-described embodiments, the case where the voltage clamp circuit has two sets each of the diode and the capacitor is shown, but of course, when the voltage clamp circuit is composed of one set, that is, the voltage clamp circuit includes the diode 19, the capacitor 25, the diode 20 and the capacitor 26. When configured, a ringing suppression circuit may be connected to each of the two diodes 11, 19 and 14, 20 connected in series.

Further, in the above-mentioned embodiments, the example of application to the three-level inverter circuit is described, but it is of course applicable to the two-level inverter circuit and the converter circuit.

[0016]

According to the present invention, it is possible to suppress the ringing phenomenon of the diode of the inverter circuit with a small number of circuit parts.
Since the malfunction of the TO gate circuit can be prevented, a compact, highly efficient, highly reliable inverter circuit can be constructed.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of an inverter circuit of the present invention.

FIG. 2 is a circuit diagram of another embodiment of the inverter circuit of the present invention.

FIG. 3 is a circuit diagram of another embodiment of the inverter circuit of the present invention.

FIG. 4 is a circuit diagram of another embodiment of the inverter circuit of the present invention.

FIG. 5 is a circuit diagram of another embodiment of the inverter circuit of the present invention.

FIG. 6 is a main circuit diagram of a three-level inverter.

FIG. 7 is a circuit diagram of one phase of an inverter.

FIG. 8 is a voltage waveform diagram of a snubber diode and a voltage waveform diagram of a GTO.

FIG. 9 is a voltage-current waveform diagram of a snubber diode.

FIG. 10 is an inverter circuit diagram in which a conventional ringing suppression circuit is connected.

FIG. 11 is a voltage waveform diagram of a diode.

[Explanation of symbols]

1 to 4 ... GTO, 5 to 8 ... free wheel diode,
9, 10 ... Anode reactor, 11-14 ... Snubber diode, 15-18 ... Snubber capacitor, 19-22
... Voltage clamp circuit diode, 23, 24 ... Clamp diode, 25-28 ... Voltage clamp circuit capacitor, 29, 30 ... Power supply capacitor, 31, 32 ... DC power supply, 33, 34 ... Energy regeneration circuit, 35 ... Resistor, 36
... Output terminal.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Narita 7-2-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Electric Power & Electric Development Division (72) Inventor Kenichi Onda Omika-cho, Hitachi-shi, Ibaraki 7-2-1, Hitachi Ltd. Electric Power & Electric Development Division

Claims (5)

[Claims] 1. An inverter circuit comprising a plurality of snubbers and a voltage clamp circuit diode connected in series,
An inverter circuit characterized in that a series circuit of two sets of resistors and capacitors having different constants is connected to each diode. 2. The inverter circuit according to claim 1, wherein one of the two series circuits of the resistor and the capacitor is connected to only the capacitor. 3. An inverter circuit for collectively connecting a series circuit of a resistor and a capacitor to the plurality of snubbers and voltage clamp circuit diodes connected in series. 4. The inverter circuit according to claim 1, wherein a series circuit of two sets of resistors and capacitors having different constants is collectively connected to the plurality of diodes connected in series. 5. The inverter circuit according to claim 3, wherein a snubber diode or a voltage clamp circuit diode is individually connected in series with a resistor and a capacitor, or a capacitor is connected as necessary.