JP2601860B2 - Power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) This invention has two control rectifier elements connected in series with the same polarity, and a capacitor connected in series with a parallel connection circuit of a diode and a resistor. The connected snubber circuits are connected in parallel to the control rectifiers, respectively, and apply a voltage to both ends of a series connection circuit of the control rectifiers to switch these control rectifiers at the same timing, for example, a chopper or the like. The present invention relates to a power converter.

(Prior Art) FIG. 4 is a circuit diagram showing a configuration of a conventional chopper of this type. In the figure, GTO thyristors 11 and 12 as control rectifiers are connected in series with the same polarity. These GTO thyristors 11 and 12 have snubber circuits 21 and 2 respectively.
2 is connected. In this case, the snubber circuit 21 is formed by connecting a capacitor 31 and a parallel circuit of a diode 41 and a resistor 51 in series, and the snubber circuit 22 is formed by connecting a capacitor 32 and a parallel circuit of a diode 42 and a resistor 52 in series. It has become.

Here, at both ends of the series circuit of the GTO thyristors 11 and 12,
A power supply voltage E is applied via a load, and
Since the GTO thyristors 11 and 12 are switched by signals having the same timing, basically the same current flows through the capacitors 31 and 32. However, actually, slightly different currents flow through the capacitors 31 and 32 due to variations in the elements and the like.

For reference, FIG. 2 (a) shows the discharge current flowing through the capacitors 31, 32 when the GTO thyristors 11, 12 are turned on. I ₁ is the capacitor 31
→ Resistor 51 → GTO thyristor 11 → Discharge current flowing in the loop of capacitor 31; i ₂ is capacitor 32 → Resistance 52 → GTO thyristor 12 → Discharge current flowing in the loop of capacitor 32, both of which are shaded due to variations in the elements. They differ by the amount shown.

Here, when the GTO thyristors 11 and 12 are both healthy, they share the voltage E almost equally, so that the discharge current
i ₁ and i ₂ are also substantially equal.

When the above-described discharge currents i ₁ and i ₂ flow through the resistors 51 and 52, they consume power W (w) represented by the following equations, respectively.

Where C: capacitance of capacitor (μF) E / 2: charging voltage of capacitor (v) f: switching frequency (Hz)

However, if any one of the GTO thyristors 11 and 12 is broken for some reason and becomes conductive,
Capacitor 31 or 3 connected to a healthy GTO thyristor
2 is charged at twice the voltage E of the normal, whereby as shown in FIG. 2 (b), flowing the maximum value is substantially twice the current i _4.

In general, if one of the two GTO thyristors connected in series is destroyed, the remaining one is applied with a doubled voltage, which is likely to be subsequently destroyed. , Continue to work.

In this case, the so-called loss power W (w) consumed by the resistance of the snubber circuit of the healthy GTO thyristor is given by the following equation. Which is four times the normal loss shown in the above equation (1).

If the operation continues for a long time, the resistance of the snubber circuit on the healthy GTO thyristor side will be heated, resulting in a very dangerous state such as burnout.

In order to solve such a problem, a means for detecting that one GTO thyristor has been destroyed and stopping the operation of the other GTO thyristor is required. Therefore, in Fig. 4, GT
O Thyristors 11 and 12 are connected to DC instrument transformers (hereinafter
DCTOs 61 and 62 were connected, and the anode-cathode voltage of each GTO thyristor 11 and 12 was detected to determine the failure of each GTO thyristor.

(Problems to be Solved by the Invention) However, in the method of measuring the voltage of the GTO thyristor by DCPT, a DCPT having a high withstand voltage is required, so that both the weight and the outer shape become large. Also, GTO
Since one DCPT is required for one thyristor,
In a chopper having a large number of sets of two series GTO thyristors, there is a problem that the weight and the outer shape are increased, and the number of signal lines drawn from the DCPT is increased, so that the structure is significantly complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is possible to detect an abnormality such as a short circuit of a control rectifying element with a minimum number of components, thereby reducing the weight, external shape, and simplifying the configuration. It is an object of the present invention to obtain a power conversion device that can be used for power conversion.

[Configuration of the invention]

(Means for Solving the Problems) According to the present invention, a snubber circuit in which two control rectifying elements are connected in series with the same polarity and a capacitor is connected in series to a parallel connection circuit of a diode and a resistor is provided as the control rectifier. In a power converter that is connected in parallel to each element and applies a voltage to both ends of a series connection circuit of the control rectifier, and performs a switching operation of these control rectifiers at the same timing, the power converter has a pair of primary windings. One of the primary windings is connected in series to the resistor of one of the snubber circuits, and the other one of the primary windings is connected to the other so that currents in opposite directions flow for each of the pair of primary windings. A current transformer connected in series to the resistor of the snubber circuit, and a detection circuit for detecting a secondary winding current of the current transformer. It is characterized by detecting an abnormality such as a short circuit.

(Operation) In the present invention, when both of the control rectifiers connected in series are sound, substantially the same current flows through the resistance of the snubber circuit connected in parallel to the control rectifier,
If one of the control rectifiers is in an abnormal state, such as a short circuit, the current balance is skillfully utilized, so that the current in the opposite direction flows through the primary winding of the pair of current transformers. Either primary winding is connected in series with the resistance of one snubber circuit, and the other primary winding is connected in series with the resistance of the other snubber circuit, and a signal generated in the secondary winding of this current transformer is detected. With such a configuration, it is possible to detect an abnormality such as a short circuit of the control rectifier with a minimum number of components, thereby achieving reduction in weight and outer shape and simplification of the configuration.

(Embodiment) FIG. 1 is a circuit diagram showing a configuration of an embodiment of the present invention. In the drawing, components denoted by the same reference numerals as those in FIG. 4 indicate the same elements. An instrument current transformer (hereinafter referred to as CT) 7 having two primary windings is used in place of the DCPTs 61 and 62 in FIG. 4 so that currents in opposite directions flow through these primary windings. One of them is connected to the resistor 51 in series, and the other is connected to the resistor 52 in series. A load is connected to the secondary winding of the CT 7, and a voltage generated at the load resistor 8 is detected by a detection circuit 9.

The operation of the present embodiment configured as described above will be described below.

First, when both the GTO thyristors 11 and 12 are normal, substantially the same voltage is applied to the capacitors 31 and 32 forming the snubber circuits 21 and 22, so that substantially the same current flows through the resistors 51 and 52. Assuming that the current flowing through the resistor 51 is i ₁ and the current flowing through the resistor 52 is i ₂ , one of the primary windings of the CT 7 has the second
Current i ₁ flows as shown in FIG. (A), the other of the primary winding of the CT7 current flows i ₂ shown in FIG. 2 (a). Therefore, as shown in FIG. 2 (b), only the current i ₃ (= i ₁ −i ₂ ) caused by the characteristic variation flows through the entire primary winding. This means that the secondary winding current of the CT 7 is also small in proportion to the current i ₃ , and the voltage generated at the load resistor 8 is negligibly small.

Next, when the GTO thyristor 11 is normal and the GTO thyristor 12 is broken and becomes conductive, when the power supply voltage is normal, only half of the power supply voltage E / 2 is applied. Since E is applied, a current having a peak value almost doubled flows through the resistor 51 of the snubber circuit 21. Therefore, as a whole of the primary winding, FIG.
As shown in greater current i ₄ to flow amplitude, the voltage corresponding to this current waveform is generated in the load resistor 8. Here, assuming that the detection circuit 9 detects a voltage corresponding to a current equal to or higher than the detection level L shown in FIG.
By current i ₄ flows can either one of the CTO thyristor 11, 12 detects that the fracture.

Thus, when the detection circuit 9 detects the destruction of the GTO thyristor on one side, if the switching of the GTO thyristor on the healthy side is stopped, the heating and burning out of the resistance of the snubber circuit connected in parallel to the GTO thyristor on the healthy side will be reduced. It can be prevented and the possible destruction of the GTO thyristor can be prevented.

FIG. 2 is a circuit diagram showing a configuration of another embodiment of the present invention, and shows a case where the present invention is applied to a type in which two-arm choppers A and B can be put in the same tank. In the figure, snubber circuits 21 and 22 are connected in parallel to GTO thyristors 11 and 12 connected in series, and
Snubber circuits 23 and 24 are connected in parallel to the thyristors 13 and 14, respectively. Here, the snubber circuit 23 is a capacitor 33
And a parallel circuit of a diode 43 and a resistor 53 are connected in series. The snubber circuit 24 is formed by connecting a capacitor 34 and a parallel circuit of a diode 44 and a resistor 54 in series. In FIG. 1, a CT7 having two primary windings is used.
T10 is used. And of these primary windings
The first primary winding and the second primary winding are connected in series with the resistors 51 and 52 so that the current directions are opposite to each other, and the third primary winding and the fourth primary winding are connected. The windings are connected in series with the resistor 53 and the resistor 54 so that the directions of the currents are reversed.

According to this configuration, there are four GTO thyristors 1 in total.
If any one of 1,12,13,14 is destroyed, a large current imbalance will occur, and the magnetic velocities will not cancel each other,
A large current flows through the secondary winding of the CT 10 and is detected by the detection circuit 9.

Thus, according to this embodiment, one of the four GTO thyristors can detect that one of the four GTO thyristors has been destroyed, so that the size and weight can be further reduced as compared with the above-described embodiment. Is achieved.

Further, even if the chopper has three or more pairs of arms in which two GTO thyristors are connected in series, if only one of the GTO thyristors is detected to be destroyed, the number of arms may be changed. One of the primary windings is connected in series to the resistor of one of the snubber circuits so that currents in opposite directions flow through each of the pair of primary windings. Is connected in series with the resistor of the other snubber circuit, and if the current generated in the secondary winding of this CT is detected, only one CT and one detection circuit are required, which makes the device even more compact. Weight and weight reduction.

In the above embodiment, the case where the present invention is applied to a chopper made of a GTO thyristor has been described.However, the present invention is not limited to this, and even when another control rectifying element such as a transistor or a thyristor is used, The present invention can be applied to all the control rectifiers having the same snubber circuit as described above.

〔The invention's effect〕

As apparent from the above description, according to the present invention, one of the primary windings is connected to the resistance of one of the snubber circuits so that a current in the opposite direction flows through the primary windings of the pair of current transformers. , The other primary winding is connected in series to the resistance of the other snubber circuit, respectively, to detect the signal generated in the secondary winding of this current transformer. The detection can be performed with a minimum number of parts, whereby the weight, the outer shape can be reduced, and the configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing the configuration of one embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing the relationship between time and current for explaining the operation of the embodiment, FIG. 3 is a circuit diagram showing the configuration of another embodiment of the present invention, and FIG. As a conversion device,
FIG. 3 is a circuit diagram illustrating a configuration of a chopper using a GTO thyristor. 11-14: GTO thyristor, 21-24: Snubber circuit, 3
1-34… Capacitor, 41-44… Diode, 51-54…
... Resistance, 7 ... Current transformer for instrument, 8 ... Resistance, 9 ... Detection circuit.

Claims (1)

(57) [Claims] 1. A snubber circuit in which two control rectifiers are connected in series with the same polarity and a capacitor is connected in series with a parallel connection circuit of a diode and a resistor are connected in parallel to the control rectifier, respectively. In a power converter that applies a voltage to both ends of a series connection circuit of control rectifiers and performs a switching operation of these control rectifiers at the same timing, the power converter has a pair of primary windings, and the pair of primary windings One of the primary windings is connected in series to the resistance of one of the snubber circuits, and the other one of the primary windings is connected in series to the resistance of the other snubber circuit so that currents in mutually opposite directions flow each time. A connected current transformer, and a detection circuit for detecting a secondary winding current of the current transformer, and detecting an abnormality such as a short circuit of the control rectifier element by an output of the detection circuit. Electric power converter according to symptoms.