JPH08111930A - Over-current protection and over-current protection apparatus for gto invertor - Google Patents

Abstract

PURPOSE: To permit blow of only one fuse, when over-current is detected, for a 3-phase circuit by increasing a load current while a gate output pattern of the PWM control signal of an inverter is fixed. CONSTITUTION: An apparatus is provided with a sine wave generating circuit 7 which holds oscillation with an output of a comparator 6 when an over-current is generated and a saw-tooth wave generating circuit 20 and a current detected by a current detecting circuit 5 is compared with a threshold value with a comparator 6. When an over-current is detected, an output signal of the comparator 6 is supplied to the sine wave generating circuit 17 and saw-tooth wave generating circuit 20 to hold oscillation of saw-tooth wave and sine wave. When an output current increases, a fuse blows. In this case, a pattern flowing through GTO of an inverse converter is any one of the patterns of P side element →load → N side element 2, two P side elements → load → N side element or P side element → load → N side element. As a result, the fuse to be blown can be limited only one fuse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent protection method and an overcurrent protection device for a GTO inverter using a gate turn-off thyristor (hereinafter referred to as GTO) as a main circuit element.

[0002]

2. Description of the Related Art Conventionally, an inverse conversion unit of an inverter using a GTO as a main circuit element is constructed as shown in FIG. 3, for example, and as a method of protecting each GTO from damage due to overcurrent, as shown in FIG. A fuse was connected in series with the GTO to emphasize protection. The device of FIG. 3 is configured to generate a PWM signal by comparing a triangular wave and a sine wave,
A DC smoothing capacitor C is connected between the DC buses P and N. GU, GV, GW, GX, GY, and GZ are GTOs that switch the main circuit current, and each of these GTs.
O is a flywheel diode DU, DV, DW,
DX, DY, DZ, snubber diodes DSU, DSV,
DSW, DSX, DSY, DSZ, snubber capacitor C
SU, CSV, CSW, CSX, CSY, CZZ, snubber discharge resistors RSU, RSV, RSW, RSX, RSY,
RSZ is connected. Also, each GTO has di / dt
Suppression reactor LU, LV, LW, LX, LY, LZ
And GTO protection fuses EFU, EFV, EFW,
EFX, EFY, and EFZ are each connected in series.

ZU, ZV and ZW represent load impedances, and 1, 2, 3 and 4 are current transformers for current detection. 5
Is a current detection circuit (output current may be detected in two-phase or three-phase, or direct current may be detected). 6 is a comparator for comparing the detected current value of the current detection circuit 5 with the overcurrent threshold value, 7 is a frequency command setting device 8 and a voltage command setting device 9
The sine wave generating circuit 10 generates a sine wave signal based on the set value of 1. 11 is a PWM generation circuit, 12 is an all-phase firing circuit, 13 is a gate cutoff circuit, 14
Is a gate amplifier circuit.

In the device constructed as described above, the protection operation of each GTO is as follows. First, when an overcurrent occurs, the current is detected by the current detection circuit 5 and compared with the overcurrent threshold value by the comparator 6. If the detected current value is equal to or greater than the threshold value, a signal is output from the comparator 6 to activate the all-phase firing circuit 12, and the gates of the GTOs are all-phase fired. This causes the inverter to short-circuit vertically, the fuse is blown, and the GT
O is protected.

[0005]

Generally, in an inverter using a transistor, when an overcurrent is detected, the base signal is cut off and the transistor is turned off to protect the element. However, due to the characteristics of the element, GTO
If the gate is cut off when the current exceeds a certain level (controllable current), it will be damaged. Therefore, when the current flows above a certain level, it is necessary to fuse the fuse and protect the GTO without interrupting the gate of the GTO.

Of course, in the controllable range, protection by shutting off overcurrent is also possible like the transistor. However, since the controllable current range largely depends on the peripheral characteristics (snubber circuit, etc.) in addition to the element characteristics, it is lower than the overcurrent withstand value of the element in a normal device. In other words, from the performance of the device, it is much better to use the device within the controllable range and protect it with a fuse by using the overcurrent withstanding capability of the device than by detecting the overcurrent and protecting it by gate interruption.

However, in the system in which the GTO is protected by detecting an overcurrent and causing a vertical short circuit to blow the fuse, at least three fuses are blown when all phases are ignited. In addition, even if an overcurrent generation classification circuit is provided to limit the phases of overcurrent generation, a short circuit of two phases is required and at least 2
The fuse of the book is blown, and the cost increases due to the provision of the sorting circuit.

The present invention has been made in view of the above points, and an object thereof is to fuse at least one fuse per three-phase circuit without short-circuiting all phases as in the conventional case or providing a classification circuit. An object of the present invention is to provide an overcurrent protection method and an overcurrent protection device for a GTO inverter.

[0009]

According to the present invention, (1) a GTO having an inverse conversion section formed by bridge-connecting gate turn-off thyristors and performing overcurrent protection by a fuse connected in series to each of the gate turn-off thyristors. In an inverter overcurrent protection method, when an overcurrent is detected, the gate output pattern of the PWM control signal of the inverter is fixed to increase the load current, and the fuse is blown to perform overcurrent protection. 2) Detecting the current of the inverter in an overcurrent protection device of a GTO inverter, which has an inverse conversion unit formed by bridge-connecting gate turn-off thyristors, and performs overcurrent protection by a fuse connected in series to each of the gate turn-off thyristors However, if the detected current is larger than a predetermined threshold, A current detection circuit, a circuit for generating a PWM control signal, and a triangular wave generation circuit and a sine wave generation circuit that fix the output level when a signal is emitted from the overcurrent detection circuit. Characteristic,
(3) In an overcurrent protection device of a GTO inverter, which has an inverse conversion unit formed by bridge-connecting gate turn-off thyristors, and which performs overcurrent protection by a fuse connected in series to each of the gate turn-off thyristors, An overcurrent detection circuit which detects and outputs a signal when the detected current is larger than a predetermined threshold;
A gate hold circuit is provided which is inserted in an electric path connecting the M control signal generating circuit and the gate circuit to allow a signal to pass therethrough at all times and which holds a gate pattern when a signal is issued from the overcurrent detection circuit. Is characterized by.

[0010]

When the overcurrent is detected, the gate output pattern of the PWM control signal is fixed. Therefore, the gate currently output is fixed as it is, and new switching is not performed. This increases the output current and blows the fuse. Here, the pattern in which the current flows to the GTO of the inverse conversion unit is (1) a pattern passing through one P-side element → load → two N-side elements, and (2) a P-side element two → load → one N-side element. It is either a passing pattern, or (3) a pattern passing through one P-side element → load → one N-side element. Therefore, when the gate pattern is fixed as described above, the fuses connected to each GTO are Fusing is required for one phase, that is, one. Therefore, it is much more economical than the conventional one.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the present invention, when an overcurrent occurs, the gate output pattern at that time is held as it is, and the GTO is protected until the fuse is blown. 1, the same parts as those in FIG. 3 are indicated by the same reference numerals. 1 is different from FIG. 3 in that all-phase firing circuit 12 is removed and a sine wave generating circuit 17 and a triangular wave generating circuit 20 whose oscillation is held by the output of comparator 6 when an overcurrent occurs are provided. The other parts are configured the same as in FIG.

In the device constructed as described above, the protection operation when an overcurrent occurs is as follows. (1) The current detected by the current detection circuit 5 is compared with a threshold value by the comparator 6 to determine an overcurrent.

(2) When an overcurrent occurs (when the detected current value is larger than the threshold value), the output signal of the comparator 6 is supplied to the sine wave generating circuit 17 and the triangular wave generating circuit 20 to generate a triangular wave or a sine wave. Hold oscillation (fix current output level).

(3) As a result, the gate currently output is fixed, and new switching is not performed.

(4) The output current increases and the fuse blows. Here, the pattern in which the current flows through the GTO of the inverse conversion unit is a pattern passing through one P-side element → load → two N-side elements, or a pattern passing through two P-side elements → load → one N-side element, It is one of the patterns passing through one P-side element → load → one N-side element. Therefore, when the gate pattern is fixed as described above, the fuse connected to each GTO needs to be blown for one phase, that is, one fuse.

Next, another embodiment of the present invention will be described. Figure 2
3 are designated by the same reference numerals. 2 is different from FIG. 3 in that all-phase firing circuit 12
The gate hold circuit 30 is provided instead of the above, and the other parts are configured the same as in FIG. The gate hold circuit 30 is a gate pattern latch circuit, which normally passes a gate signal, but latches the pattern when a signal is input from the comparator 6.

In the device constructed as described above, the protection operation when an overcurrent occurs is as follows. (1) The current detected by the current detection circuit 5 is compared with a threshold value by the comparator 6 to determine an overcurrent.

(2) When an overcurrent occurs (when the detected current value is larger than the threshold value), the output signal of the comparator 6 is supplied to the gate hold circuit 30, and the gate hold circuit 30 holds the gate pattern. (Fix current output level).

(3) As a result, the gate currently output is fixed, and new switching is not performed.

(4) The output current increases and the fuse blows. Here, the pattern in which the current flows through the GTO of the inverse conversion unit is a pattern passing through one P-side element → load → two N-side elements, or a pattern passing through two P-side elements → load → one N-side element, It is one of the patterns passing through one P-side element → load → one N-side element. Therefore, when the gate pattern is fixed as described above, the fuse connected to each GTO needs to be blown for one phase, that is, one fuse.

[0021]

As described above, according to the present invention, in the case where overcurrent protection is performed by the fuse connected in series to the GTO, when the overcurrent is detected, the gate output pattern of the PWM control signal of the inverter is fixed and the load is applied. Since the current is increased and the fuse is blown for overcurrent protection, at least one fuse needs to be blown, which is very economical compared to the conventional method.

[Brief description of drawings]

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

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

FIG. 3 is a circuit diagram showing an example of a conventional GTO inverter overcurrent protection method.

[Explanation of symbols]

GU, GV, GW, GX, GY, GZ ... Gate turn-off thyristor EFU, EFV, EFW, EFX, EFY, EFZ ... G
Fuse for TO protection 1, 2, 3, 4 ... Current transformer 5 ... Current detection circuit 6 ... Comparator 7, 17 ... Sine wave generation circuit 10, 20 ... Triangle wave generation circuit 30 ... Gate hold circuit

Claims (3)

[Claims] 1. An overcurrent detection method for a GTO inverter, comprising an inverse conversion unit formed by bridge-connecting gate turn-off thyristors, and performing overcurrent protection by a fuse connected in series to each of the gate turn-off thyristors. In some cases, the gate output pattern of the PWM control signal of the inverter is fixed, the load current is increased, and the fuse is blown to perform overcurrent protection. 2. An overcurrent protection device for a GTO inverter, which has an inverse conversion part formed by bridge-connecting gate turn-off thyristors, and performs overcurrent protection by a fuse connected in series to each of the gate turn-off thyristors. An overcurrent detection circuit which detects a current and outputs a signal when the detected current is larger than a predetermined threshold, and a circuit for generating a PWM control signal, wherein the overcurrent detection circuit generates a signal. An overcurrent protection device for a GTO inverter, which is provided with a triangular wave generation circuit and a sine wave generation circuit that fix an output level when the GTO inverter is turned on. 3. An overcurrent protection device for a GTO inverter, which has an inverse conversion part formed by connecting gate turn-off thyristors in a bridge connection and performs overcurrent protection by a fuse connected in series to each of the gate turn-off thyristors. An overcurrent detection circuit that detects a current and outputs a signal when the detected current is larger than a predetermined threshold value, and is inserted in a circuit that connects the PWM control signal generation circuit and the gate circuit, and always passes the signal. An overcurrent protection device for a GTO inverter, further comprising: a gate hold circuit that holds a gate pattern when a signal is issued from the overcurrent detection circuit.