JPS6146196A - High speed overcurrent suppressing device - Google Patents

Abstract

PURPOSE:To eliminate the stop of the operation of an inverter itself by an overcurrent by interposing an analog switch in a pulse width controller, and controlling to conduct an inversion unit by turning ON and OFF the overcurrent. CONSTITUTION:An analog switch 10 is interposed in a pulse width controller for controlling to conduct a control element in an inversion unit of an inverter 4, a current detected by a current detector 5 is input to a hysteresis comparator 9, and the switch 10 is controlled to be opened or closed by the output signal. Thus, the conduction control of the inversion unit is rapidly stopped for an overcurrent generated by a very rapid variation, and when the overcurrent decreases to the prescribed level of lower, the conduction control of the inversion unit is immediately reopened, and the inverter itself is stopped in operation during the period.

Description

Detailed Description of the Invention (Technical Detail) The invention of this application detects an overcurrent flowing through an inverter, stops conduction control of only the forward conversion section or the inverse conversion section of the inverter, and prevents the overcurrent from falling below a predetermined level. This invention relates to a high-speed overcurrent suppressing device that restarts conduction control when the current level decreases, and does not stop the operation of the inverter itself during that time.

(Prior art) When an inverter controls the speed of a load, such as an electric motor, an overcurrent may flow to the inverter due to a ground fault or overload. A method based on peak current detection and a method based on peak current detection are known.

The analog loop system has a one-iner analog loop for overcurrent suppression installed in parallel with the inverter speed control loop, detects overcurrent flowing through the inverter, and controls conduction of the thyristor to suppress the overcurrent. However, the current detection signal extracted contains a large amount of ripple.
A filter is used to remove this ripple.

Filters have second-order delay characteristics, which inevitably causes a delay in response, but since it is technically impossible to reduce this delay to zero, it is necessary to spend as much time as possible to reduce the overcurrent. need to be suppressed. Therefore, although the response time of the analog loop for overcurrent suppression is set to about 10 milliseconds, it is difficult to respond to overcurrents that occur faster than this response time. Such overcurrents that occur quickly have been dealt with by stopping the operation of the inverter itself.

In addition, the method based on peak current detection detects the peak value of overcurrent, and if the peak value exceeds a predetermined value,
Each time, the problem was dealt with by stopping the operation of the inverter itself.

Either method stops the operation of the inverter itself, so if it is used on a production line, it inevitably reduces productivity, and in some cases, product uniformity cannot be guaranteed. was there.

(Purpose) The invention in this question is to eliminate the drawbacks of the prior art described above, and the first invention is to configure the inverse conversion section with a gate turn-off thyristor or a nower transistor. Quickly detects overcurrent flowing through the inverter, stops conduction control of the inverter, and resumes conduction control of the inverse converter when the overcurrent level drops to a predetermined value, thereby stopping the operation of the inverter itself. The purpose of the second invention is to provide a high-speed overcurrent suppressing device that does not cause problems, and the second invention achieves the same object as the first invention. It quickly detects overcurrent flowing through the inverter, which is made up of transistors, stops the conduction control of the forward conversion section, and restarts the conduction control of the forward conversion section when the overcurrent level drops to a predetermined value. The purpose of the present invention is to provide a high-speed overcurrent suppression device that does not stop operation.

(Summary of the Invention) The invention in Part 1 of this application rectifies the input current using a forward conversion section, controls conduction and conduction of an inverse conversion section including a gate turn-off thyristor or a four-power transistor, and converts the input current into a load. In an inverter that supplies a control current, an overcurrent is detected by a current detection element installed in the inverter, and this is converted to an absolute value and input to a hysteresis comparator.The hysteresis comparator compares the detected current with the reference A comparison is made with the current, and when the value of the detected current exceeds the reference current value, a high level signal is output, and the analog switch inserted in the pulse width control circuit that controls the conduction of the inverse conversion section is Add a high level signal to open the
This prevents the transmission of the pulse width signal to the inverse converter,
Stops conduction control of the inverse converter. When the detected current value drops to a value lower than the reference current value, a low level signal is output, which is input to the analog switch to close it, and a pulse width signal is transmitted to the inverse conversion section to perform inverse conversion. The inverter itself will not be stopped during this period.

According to the second invention of this publication, conduction control is performed so that the load voltage is constant by a forward conversion section including a gate turn-off thyristor or a power transistor, and conduction control of an inverse conversion section is performed to control the load. In an inverter that supplies current, an overcurrent is detected by a current detection element installed in the inverter, converted to an absolute value and input to a hysteresis comparator, and the hysteresis comparator compares the detected current with a reference current. When the detected current value exceeds the reference current value, an output level signal is output to control the conduction of the forward conversion section described above.The analog switch inserted in the I pulse width control circuit is connected to the A low level signal is applied to open the switch, and when the value drops to a value lower than the Δ value to the forward conversion section, a low level signal is output, which is input to the analog switch to close it, and the pulse width to the forward conversion section is set. The signal is transmitted and the conduction control of the forward conversion section is restarted, but the operation of the inverter itself is not stopped during this period.

(Example) Examples of the high-speed overcurrent suppression device of the first invention and the second invention of this application will be described below.

FIG. 1 shows an embodiment of the first invention of this application, which stops the conduction control of the inverter's inverter when an overcurrent occurs, and resumes the conduction control when the overcurrent level falls below a predetermined value. It is a 2-dimensional diagram.

In the figure, the inverter includes a forward converter 1, a DC reactor 2, a smoothing capacitor 3, and an inverse converter 4, and controls the speed of an electric motor, which is a load. The forward converter 1 is composed of a diode rectifier, and converts alternating current input from a commercial power source (not shown) into direct current, the direct current reactor 2 absorbs ripples of the direct current, and the smoothing capacitor 3 smooths it. It is input to the inverse transformer 4.

Next, the overcurrent detection and analog switch control circuit will be explained.

Reference numeral 5 denotes a current detector such as a shunt resistor, which is connected in series with the inverter 4 and detects current when the inverter is running and regenerating. A DC/DC converter 6 converts the high voltage direct current detected by the shunt resistor 5 into a low voltage direct current. Reference numeral 7 denotes an absolute value circuit which takes the absolute value of the current value detected by the shunt resistor 5 and having different polarities during power running and regeneration of the inverter. 8 is a current setter that outputs a reference value, and 9 is a hysteresis comparator, which compares the level of the reference signal output from the current setter and the detected current output from the absolute value circuit 7, and calculates the detected current. When the detected current value exceeds the reference current value, that is, when an overcurrent occurs, a -・irrepel signal is output, and when the detected current value decreases to a value that is much lower than the reference current value, that is, the overcurrent level is It has a hysteresis characteristic that outputs a low level signal when the voltage drops below a predetermined value or under normal conditions. The output signal of the hysteresis comparator 9 is input to an analog switch 20 such as a FET, and when the Helepel signal is applied, the analog switch 10 is open, and when a low level signal is input, the analog switch 10 is closed.

In this way, the analog switch 1o is controlled to open and close by the comparator 9 having hysteresis characteristics, and transmits and blocks the Nockles width signal, which will be described later, so that the control system can be controlled stably without causing hunting. - Next, the pulse width control circuit that controls conduction of the inverse conversion section will be explained.

Reference numeral 11 denotes a voltage frequency converter which, when a command voltage from a voltage setting device (not shown) is input, generates a digital signal having a frequency corresponding to this analog voltage, and inputs this to the counter 2. 13 is a sine wave mech with ROM,
The count output of the counter 12 is inputted as an address, and the digital sine wave signals stored in the ROM are read out one after another and are read out at 94. The signal is input to the converter 1511C, converted to an analog sine wave signal, and input to the comparator 17.

Note that the sine wave memory 13, the converter 15, and the comparator 1
7, f-) circuit 18, which will be described later, and analog switch 1.
0 and an amplifier 19 are provided, and are configured to generate cell width signals with a phase difference of 120 degrees; Since they differ only in the points that occur, they are illustrated as a single entity to avoid complicating the explanation.

14 is a carrier wave having a ROM, for example, a triangular wave memory; the counting output of the counter 12 is similarly inputted to the address, and the digital triangular wave signals stored in the ROM are read out one after another and sent to the transfer unit 16. The signal is inputted, converted into an analog triangular wave signal, and inputted to the comparator 12. The triangular wave memo IJ 14 is configured to output a digital triangular wave signal having a frequency corresponding to the count output of the counter 12.

The comparator 17 compares the levels of the sine wave signal and the triangular wave signal, and outputs a pulse when the imaging width of the sine wave signal is larger than that of the triangular wave signal, and outputs a pulse between -. Outputs a signal with unequal width.

18 is a dirt circuit, onff-) signal generation circuit 18□
and an off-gate signal generation circuit 182, which adds an on-gate signal and an off-gate signal to the element group of the inverse converter 4 to perform on/off control. In this way, the gate turn-off thyristor of each phase of the inverse converter is controlled to conduct by the on-gate signal and the off-gate signal, and an alternating current pulse current of unequal width is supplied from the inverter 4 to the motor M. do.

The analog switch 10 closes when the low level signal from the hysteresis comparator 9 is input, and ? -) Circuit 1
8 and the amplifier 19 are electrically connected to transmit the elbow width signal to the inverse converter 4, and when the -.repel signal is input, it is opened, and the electrical connection between the r-t circuit J8 and the amplifier 19 is The transmission of the Nockles width signal to the inverse converter 4 is blocked.

To explain the operation of the device having such a configuration, in normal times, the DC current output from the forward converter 1 is smoothed by the DC reactor 2 and the smoothing capacitor 3,
It is added to the inverse converter 4, and an alternating current of unequal width is applied to the electric motor M.
? A pulse current is supplied.

The current flowing through the inverter is detected by a shunt resistor 5, converted to a low voltage DC signal by a D%C converter 6, and inputted to a hysteresis comparator 9 via an absolute value circuit 7. The hysteresis comparator 9 performs a level comparison between the detected current value from the absolute value circuit 7 and the reference signal of the current setter 80, but under normal conditions, the detected current value does not exceed the reference current value, so a low level signal is generated. is output, and the analog switch 10 is closed. 9, e-) The circuit 18 and the amplifier 19 are electrically connected, allowing transmission of a pulse width signal.

On the other hand, the digital signal from the voltage frequency converter 11 is input to a counter 12, and the count output of the counter 12 is input to a sine wave memory 13 and a triangular wave memory 14. The digital sine wave signal read out from the sine wave memory 13 is
The signal is input to the A converter 15, converted to an analog sine wave signal, and input to the comparator 17. Also, triangular wave memory 1
The digital triangular wave signal read from 4 is input to the D/A converter 16, converted to an analog signal, and sent to the comparator 17.
is input. The comparator 17 compares the levels of the sine wave signal and the triangular wave signal and outputs a 4 pulse width signal, which is then sent to the on-gate signal generation circuit 181 of the dart circuit 8.
1 Off gate signal generation circuit 182, analog switch 1
0 is input to the inverse transformer 4 via the amplifier 19. The gate turn-off thyristor of each phase in the inverse converter 4 is controlled to be conductive, and a nollus current of unequal width is inputted from the inverter 4 to the motor M to control its speed.

In such a steady state, if a ground fault or overload occurs, an overcurrent will flow through the inverter, but this overcurrent is detected by the shunt resistor 5 and transmitted via the D%C converter 6 and the absolute value circuit 7. The detected current is input to the hysteresis comparator 9. The hysteresis comparator 9 compares the detected current value with the reference value of the current setter 8, but since an overcurrent has occurred, the detected current value exceeds the reference value and outputs a -.level signal. - The analog switch 10 to which the illegal signal is input is opened and prevents the transmission of the pulse width signal from the r-to circuit 18 to the amplifier 19.

As a result, the conduction control operation of the inverter 4 is stopped, but the regenerated power from the motor M is regenerated to the smoothing capacitor 3 through the feedback diode of the inverter 4, and the operation of the inverter itself is not stopped. .

When the overcurrent decreases, the shunt resistor 5 detects this,
The signal is input to a hysteresis comparator 9 via a DC/DC converter 6 and an absolute value circuit 7. The hysteresis comparator 9 compares the level of the detected current value with the reference signal of the current setter 8, and outputs a low level signal when the detected current value decreases to a value lower than the reference signal value. In addition to the analog switch 10, it is closed.

As a result, the pulse width signal output from the comparator 12 is input to the inverse converter 4 via the dart circuit 18 and the amplifier 19, and the conduction control of the gate turn-off thyristor of the inverse converter 4 is immediately performed. The operation is restarted, and the electric motor M is again supplied with an alternating current of unequal width.

FIG. 2 shows an embodiment of the second invention in which the conduction control of the forward conversion section of the inverter is stopped when an overcurrent occurs, and the conduction control is restarted when the overcurrent falls below a predetermined level. FIG.

In the same figure, the parts denoted by the same reference numerals as those shown in FIG. 1 have already been described in the explanation regarding FIG. 1, so their speed increase will be omitted.

Reference numeral 21 denotes a forward conversion unit consisting of a gate turn-off thyristor, whose conduction is controlled by a Nockles width signal output from a pulse width control circuit to be described later, and which controls the voltage applied to the inverter from a commercial power source (not shown). Let's do it.

Next, a knowledge width control circuit that controls conduction of the forward conversion section 21 will be described.

PT is a transformer, and 22 is a voltage detection circuit including a rectifier, which detects the load voltage of the bus connecting the inverter 4 and the motor M, and converts it into a DC voltage. A comparator 23 obtains a deviation between the DC voltage eL of the voltage detection circuit 22 and a voltage setting signal output from a voltage generator (not shown), and compares this deviation signal with a carrier wave, for example, a triangular wave signal e8. A pulse width signal is output when the deviation signal exceeds that of the triangular wave signal e8. And the DC voltage eL
When the DC voltage eL is increasing or decreasing, a Nockles width signal of unequal width is output, and when the DC voltage eL is constant, a pulse width signal of equal width is output. The conduction of the gate turn-off thyristor of the forward conversion section 21 is controlled so that the load voltage applied to M is constant.

Note that although only one set of dirt circuits 25 is shown, in reality it is composed of six sets), and is shown as a single circuit to avoid complication in the explanation.

In this way, the on-gate signal and the off-gate signal from the dart circuit 25 are used to determine the ? −)・Turn off・
The conduction of the thyristor is controlled, and the voltage of the forward conversion unit 21 is controlled so that the load voltage is constant as described above.

Note that the inverse converter 4 is controlled to be conductive by a separately provided control circuit (not shown), and controls the frequency supplied to the electric motor M.

To explain the operation of the device having such a configuration, under normal conditions, the DC voltage whose conduction is controlled by the forward converter 2 is smoothed by the DC reactor 2 and the smoothing capacitor 8, and is input to the inverse converter 4. be done. As described above, the inverse converter 4 is controlled to be conductive by a separately provided control circuit (not shown), and appropriately varies the primary frequency applied to the electric motor M to control its speed.

During normal times, the detected current detected by the shunt resistor 5 connected in series with the forward converter 21 is passed through the DC/bc converter 6 and the absolute value circuit 7 to the hysteresis comparator 9.
is input. The hysteresis comparator 9 performs a level comparison between the detected current value and the reference signal value output from the current setter 8, but since it is normal, the detected current value does not exceed the reference current value, and therefore a low level signal is output. is applied to the analog switch 10 to close it and open the dirt circuit 25.
and dart amplifier 26 are electrically connected to each other, thereby making it possible to transmit a nollus width signal.

On the other hand, the load voltage detected by the transformer PT is input to the voltage detector 22, the DC voltage e converted to DC is input to the comparator 23, and this voltage eL is output from a voltage generator (not shown). A difference of 1 from the voltage setting signal is obtained, and the level is compared with the triangular wave signal es to output a /4 pulse width signal. The i4 pulse width signal is input to the f-) circuit 25 via the voltage control amplifier 24, and the on-gate signal generating circuit 251 and off-gate signal generating circuit 252 generate desired off-gate signals and off-gate signals, and each of these r −
The output signal is passed through the analog switch 1θ and the date amplifier 26 to the forward converter 21? -) - Supply to the turn-off thyristor to control conduction and perform voltage control so that the load voltage is constant.

In such a state, an overcurrent flows through the inverter when a ground fault or overload occurs, but this is detected by the shunt resistor 5, and this detected current is subjected to hysteresis comparison via the D%C converter and the absolute value circuit 7. input into device 9. The hysteresis comparator 9 compares the level of the detected current value with the basic signal of the current setter 8, but since an overcurrent is occurring, the detected current value exceeds the reference current value and outputs a high level signal.

The analog switch 10 to which the high level signal is input is opened to cut off the electrical connection between the 9,/f-) circuit 25 and the dart amplifier 26, thereby blocking the transmission of the pulse width signal to the forward converter 21. As a result, the conduction control of the forward converter 21 is stopped, but circuit devices such as the reverse converter of the inverter are operating, and the operation of the inverter itself is not stopped.

During this time, when the overcurrent falls to a predetermined level, the shunt resistor 5 detects this and inputs this detected current to the hysteresis comparator 9 via the DC/bc converter 6 and the absolute value circuit 7. The hysteresis comparator 9 detects that the value of the detected current is -
- When the reference current value reaches a value much lower than the reference current value when the high level signal is output, a low level signal is output and the analog switch 10 is closed. As a result, the electrical connection between the dart circuit 25 and the dart amplifier 26 is reestablished, and the pulse width signal is input to the r-) turn-off thyristor of the forward converter 21 to immediately resume conduction control. .

In the embodiment described above, a case has been described in which a shunt resistor is used as the current detection means of the inverter, but a Hall element may be used instead of the shunt resistor.

Furthermore, in the explanation of the above embodiments, it has been stated that overcurrent occurs due to ground faults or overloads, but the occurrence of overcurrent is not limited to this. This is caused by a locking phenomenon and further by noise inside the inverter control device.

Furthermore, as an element where current conduction is controlled? lt
? -) - Not limited to turn-off thyristors, similar effects can be achieved by using a four-power transistor that becomes conductive when a positive signal is applied and becomes non-conductive when a negative signal is applied.

(Effects) As explained above, according to the first invention of this application, the gate turn-off in the inverse conversion section of the inverter
An analog switch is interposed in the pulse 6 control circuit that controls conduction of the thyristor or power transistor, and the current detected by the current detection element is input to the hysteresis comparator, and the output signal controls the opening and closing of the analog switch. Therefore, the conduction control of the inverse converter is quickly stopped in response to an overcurrent that occurs with a very rapid change, and when the overcurrent falls below a predetermined level, the conduction control of the inverse converter is immediately resumed. There is no need to stop the operation of the inverter itself.

Further, according to the second invention of this application, an analog switch is interposed in the ankle width control circuit that controls the conduction of the gate turn-off thyristor or the power transistor in the forward conversion section of the inverter, and the current detection element The current detected by υ is input to a hysteresis comparator, and the output signal is used to control the opening and closing of an analog switch, so it is possible to quickly control the conduction of the forward conversion section in response to overcurrents that occur with very rapid changes. The inverter itself is stopped, and when the overcurrent falls below a predetermined level, the conduction control of the forward conversion section is immediately restarted, and during this period, the operation of the inverter itself is not stopped.

Thus, according to the first invention and the second invention of the application,
Not only is it possible to realize an inverter with extremely high reliability and stability, but it is also possible to realize An inverter with high performance can be realized at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a high-speed overcurrent suppressor according to the first invention of this application, and FIG. 2 is a block diagram of an embodiment of the high-speed overcurrent suppressor according to the second invention. In the figure, 1 is a forward conversion section, 2 is a DC reactor, 3 is a smoothing capacitor, 4 is an inverse conversion section including an r-to-turn-off thyristor, 5 is a shunt resistor, 6 is a DC/DC converter, and 7 is an absolute value circuit, 8 is a current setting device, 9 is a hysteresis comparator, 10 is an analog switch, 11 is a voltage frequency converter, 12 is a counter, 13 is a sine wave memory, 1
4 is a triangular wave memory, 15 and 16 are "/A converters, 17 is a comparator, 18 is a dart circuit, 181 is an on r-) signal generation circuit, 182 is an off gate signal generation circuit, 19 is an amplifier, and 21 is an a forward conversion section including a gate turn-off thyristor, 23 a voltage comparator, 24 a voltage control amplifier, 2
5 is a dart circuit, 251 is an on-gate signal generation circuit, 2
52 is an off-dirt signal generation circuit, and 26 is a dirt amplifier.

Claims (2)

[Claims] (1) In an inverter that supplies AC power to a load by rectifying the input current in the forward conversion section and controlling the conduction of the gate turn-off thyristor or power transistor in the inverse conversion section, the current provided in the inverter a detection element; a hysteresis comparator that compares the current detection signal detected by the current detection element and converted into an absolute value with a reference signal; an analog switch whose opening/closing is controlled by the output of the comparator; an on-gate signal; A high-speed overcurrent suppression device comprising: a control circuit that controls conduction of the inverse conversion section based on an off-gate signal; and the analog switch inserted in the control circuit. (2) Rectifying the input current by a forward conversion section having a gate turn-off thyristor or a power transistor,
In an inverter that supplies alternating current power to a load by controlling conduction of an inverter, a current detection element provided in the inverter, a current detection signal detected by the current detection element and converted into an absolute value, and a reference signal. a hysteresis comparator for comparison; an analog switch whose opening/closing is controlled by the output of the comparator; a control circuit that controls conduction of the forward conversion section based on the on-gate signal and the off-gate signal; and the analog switch inserted in the control circuit. A high-speed overcurrent suppression device comprising a switch.