JPS5941180A - Protecting device for power inverter - Google Patents

Abstract

PURPOSE:To protect a thyristor element by judging whether a commutation failure or not according to the value of an AC input current when the DC current of a power rectifier is interrupted at low output time or at the starting time, thereby stopping the rectifier by effectively detecting the commutation failure. CONSTITUTION:When a firing signal is applied to the thyristors 3a, 3d of a power inverter 3 from a gate signal generator to start the inverter 3, a current is supplied to a load 4. When a power rectifier 1 is interrupted at the low output time or at the starting time, this influence is presented even at the AC input side of the rectifier 1. The output signal of a current transformer 10 is converted by an AC/DC converter 11, and compared by the set value of a setter 13. When a commutation failure occurs, a gate signal for stopping the rectifier 1 is fed from a control circuit 15.

Description

[Detailed description of the invention] The present invention relates to a storage device for a current-type inverter.

As is well known, inversion devices have recently come to be widely used for controlling electric motors, induction heating F, and the like. This type of inverse converter is operated using the output of the forward converter as an input power source, but
Since the following failures and 1s occur in the inverse conversion device,
The high-I conversion device is also controlled as follows.

That is, if the inverse converter fails to commutate, the forward conversion current increases and a large current flows through the elements constituting the inverter, potentially destroying the elements.

For this reason, measures are taken to reduce or stop the output of the forward converter when the commutation failure occurs.

Conventionally, through this method, the current increases due to commutation failure,
When this current reaches the rated value of about 120 to 150, the output of the 11M converter is reduced or stopped.As a result, the control delay of the 1M converter is added to the current, and the element There is a ↑1 engineering stream with a rating of about 200 to 300.

For this reason, if the element is not equipped with something that can withstand a large current, the element may be destroyed. Further, in the case of an element that can withstand a large current, the element itself becomes large in size and expensive, resulting in a drawback that the device becomes large and the price rises.

In order to eliminate the above drawbacks, commutation, failure is set to 1*
A device equipped with a circuit for commutation was released, but this detection circuit normally determines commutation failure by detecting that the voltage between the positive and negative outputs of the forward converter has reached zero level. . In devices that make such judgments, the output of the forward converter is at zero level (when the current is intermittent) during startup or low output.
There will be one period. In such a case, if the inverse converter determines that commutation has failed, there is a risk that the output of the l1m converter may be reduced or stopped. Further, in a device equipped with the above-mentioned detection circuit, there is a risk that the operation will become unstable if the first flow of the tube is interrupted at the time of startup or at low output.

This invention was made in view of the above circumstances, and allows the device to always operate stably even if the output (DC current) of the forward converter is temporarily interrupted, and even when a commutation failure occurs. 11 What is the output of the conversion device? The purpose of the present invention is to provide a maintenance system for an inverter in which the closure of one element is actually achieved in order to reduce or stop the inverter.

Hereinafter, examples of the voting right of this invention will be explained with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a forward conversion device using thyristor elements, and the positive side of this device I is connected via a DC reactor 2 to the positive side of the human power of an inverse conversion device W3. In addition, 111 conversion device I0: negative (+411 is directly connected to the negative side of the human power of 3p conversion device 3. A load q is connected between the midpoints of the bridge circuit. 5 is a detecting section formed by a rectifier circuit consisting of a diode bridge, and this detecting section 5 detects the control output of the 111111 converter. , the human power is connected to the positive input terminal of the inverter 3 via the current limiting low loss 6.
The other end of the human power is connected to the negative input end of the inversion device 3.

The output end of the force detection section 5 is connected to the light emitting side of a photocoupler 7, which is an electrically insulated circuit, and the power end on the light receiving side is connected to one input end of an AND circuit 8. .

The light receiving side of the photocoupler 7 is connected to the source. The output terminal of a plus comparator 9 is connected to the other input terminal of the AND circuit 8. JO is a current transformer installed in the human power supply line of +111-i converter I, and the output of this current transformer IO is AC-DC! converter 1] to the matching circuit 12
is given to. A predetermined first setting is inputted to the matching circuit 12 via a setting device 13 . 14 is a diode for limiting the output polarity of the comparator 9. The output of the AND circuit 8 is input to the control circuit 15 of the 11-phase converter I. In the figure, 16 is the current diode,
17 is a current limiting resistor.

Next, the operation of the above embodiment will be described. Here, the thyristor 3a of the inverter 3,
3d to start the device 3 by giving an ignition signal. As a result, a current is supplied to the negative fR current, and the voltage vt across the load is as shown in Figure 2 (c). has a waveform as shown in Fig. 2 (A).From this point on, the inverse converter 3 is supplied with a direct current 'tK flow d (@ Figure 2), but at time T
Assume that the supply of the DC type IFva is cut off at the time of 1. Then, the DC single current 1 d gradually decreases as shown in Fig. 2 (b), and reaches zero at time T.

Then, at time T, the so-called Ill conversion device 4I is supplied again with the direct current m: IE vd to the inversion device 3.
During intermittent operation, (such Qil) operation occurs especially at start-up or at low power. ), the influence of the consort also appears on the AC input side of the forward conversion device 1. The direct current 'tYi,
When the pressure vd becomes zero, the output signal of the cooler 10 is A.
The signal is converted by the C-DC converter 11, resulting in a waveform as shown in FIG. 2 (e). The output signal of this AC-DC converter 11 is the setting value of the setting device 13 set at a level of about 120 to 150% of the rated evening current (plus V shown in Fig. 2).
When the signal is less than the set value, it becomes zero level,
When the setting is over 1 night, the output of the comparator 9 is 3.
Even when the output signal of the C-DC converter 11 becomes zero, it becomes zero level with some time lag.

When the above-mentioned Shinryu Tora and Ryukou become zero, 72 in the i4L 1 diagram
The pressure 111' (shown in FIG. 2) in between also becomes zero. Therefore, the output (+111) of the photocoupler 7 is as shown in Figure 2, and the level at the time T2 and T8 is "
1" it says.

As a result, the output of the AND circuit 8 becomes as shown in the second diagram, and the output level is zero, and the control circuit 15 sends out a gate signal to continue the operation of the 111 converter lock I without stopping.

Next, if a commutation failure occurs within the time period T2 and T3 shown in 21 ￥1 at low output, the plane: Fig. 3 (b)
An electric current (■) flows as shown in the figure. For this reason, %AC-
Since the signal d also appears at the output of the DC converter II, the signal (C) shown in FIG. As a result, the output of the AND circuit 8 becomes "1" due to the hand signal from the photocoupler 7 and the Mjl mark (No. 3), and the control circuit 15
A gate signal to stop the IIl++ converter I is sent from T of the 31st ca. The temporary cabinet 1 is stopped.

In addition, in the +A case where a commutation failure occurs at a so-called medium/high output when the force supplied to the load ψ is relatively large (1d), each circuit is The device 1 is operated and the device 1 is stopped in the same manner as shown in FIG. It is possible to reliably secure one vacancy for the Cyrisk element.

As described above, according to the present invention, when the output is low or at the beginning of 1Jij+, it is determined by the value of the AC input current whether the DC normal current of the converter is interrupted or commutation has failed. This makes it possible to reduce lE at low output or when starting.
The advantages include that operation can be continued without stopping the retraction and rotation of the i-conversion device, and in the event of a commutation failure, the continuous rotation of the device &] can be stopped by detecting (Nikosai'1). There is.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIGS. 2A to 2D are operations of the above embodiment, FIG. From Figure 4H show the operation λ 1.4 times when commutation fails. ! ...l1ll-i conversion device, 3...inverse conversion device 6''
, ψ Load, 5...Detection unit, 2...Photocoupler, 8...And[(Ji path, 9...Comparator, 10...
Variant #, device, ll...A (1!-DC converter, 12...
Matching circuit, 13... Setting device, 15... Control Fig. 4

Claims (1)

[Claims] (1) In the inverse conversion device operated by the control output of the forward conversion device, a detection section formed of a mochi flow circuit consisting of a dimate bridge that detects the control output of the forward conversion device; The output circuit detects the AC input signal of the forward converter, and when this detection signal is below a predetermined setting (iF+, no output signal is sent out, and when it is above the set point, no output signal is sent out. It is controlled by a comparator circuit that sends out a signal, a logic circuit that ANDs an output signal of this comparison circuit and an output signal of the previous H2 isolation circuit and sends an output signal, and an output signal of this logic circuit. 1. A protection device for a reverse conversion device, comprising: a control circuit for controlling operation of the forward conversion device.