JPH077993A - Inverter device - Google Patents

Abstract

PURPOSE:To rapidly stop an induction electric motor without using a mechanical type brake when the service interruption of an AC power supply occurs. CONSTITUTION:The occurrence of service interruption of a three-phase AC power supply 21 is detected by a service interruption detection circuit 39, an operation mode is switched to a deceleration mode by a deceleration mode switching circuit 29, and at the same time the deceleration time setting signal of a deceleration time setting circuit 35 is validated. Current flowing from a smoothing capacitor 24 to the side of an inverter main circuit 25 is detected by a current detector 33, and then the deceleration time setting circuit 35 sets deceleration time to a short and a long values when an induction motor 26 is in a power running state and in a regeneration state, respectively. A frequency command output circuit 30 sets the induction motor 26 to be in regeneration state, performs control so that the terminal voltage of the smoothing capacitor 24 is nearly constant, drives the inverter main circuit 25, and then rapidly stops the induction motor 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device capable of quickly stopping an AC motor when a power failure occurs in the AC power supply while the AC motor is being rotationally driven.

[0002]

2. Description of the Related Art Conventionally, as an inverter device of this type, there is one shown in FIG. 9, for example. That is, in FIG. 9, the output of the three-phase AC power supply 1 is rectified and smoothed by the rectifier circuit 2 and the smoothing capacitor 3 and is given between the power supply lines 4a and 4b. The inverter main circuit 5, which is fed from between the power supply lines 4a and 4b,
It consists of three-phase bridge connection of switching elements,
The drive signal from the drive circuit 6 supplies a three-phase AC output to the induction motor 7 as an AC motor connected to the output side.

The voltage detection circuit 8 includes power supply lines 4a and 4b.
The voltage between them is detected and the detection signal is given to the comparator 9.
A reference voltage signal for determining a power failure is given to the comparator 9 from the voltage level setter 10. And the comparator 9
Outputs a power failure detection signal Sa when the detection signal from the voltage detection circuit 8 falls below the reference voltage signal from the voltage level setting unit 10. The hold circuit 11 continues to output as the power failure signal Sb once the comparator 9 receives the power failure detection signal Sa, and applies it to the PWM signal cutoff circuit 12 and the mechanical brake device 13. There is.

The operation mode setting circuit 14 compares the target speed command fi with the output frequency command fo to select the operation mode, and supplies the frequency command output circuit 15 with the operation mode signal. The frequency command output circuit 15 determines the next output frequency command fo according to the given operation mode signal. The frequency command output circuit 15 gives the output frequency command fo to the above-mentioned operation mode setting circuit 14 and also to the PWM signal generation circuit 16. give. The PWM signal generation circuit 12 calculates a PWM signal based on the given output frequency command fo, gives a control signal to the drive circuit 6 via the PWM signal cutoff circuit 12, and turns on / off the switching element of the inverter main circuit 5. Control.

The PWM signal cutoff circuit 12 cuts off the signal from the PWM signal generation circuit 16 when the power failure signal Sb is given from the hold circuit 11.
The brake device 13 mechanically brakes the induction motor 7 when the power failure signal Sb is given from the hold circuit 11.

According to the above construction, when the target speed command fi is given in the normal driving condition, the driving mode setting circuit 14 compares the output frequency command fo output from the frequency command output circuit 15 at that time. Then, the operation mode is selected, and an operation mode signal is given to the frequency command output circuit 15. In this case, the relationship between the target speed command fi and the current output frequency command fo is set to the acceleration mode when fo <fi, the constant speed mode when fo = fi, and the deceleration mode when fo> fi.

The frequency command output circuit 15 has a frequency command fo corresponding to a pattern of acceleration, constant speed or deceleration mode.
Is calculated and given to the PWM signal generation circuit 16. The PWM signal generation circuit 16 generates a PWM signal based on the frequency command fo, and the drive circuit 6 via the PWM signal cutoff circuit 12.
In the main inverter circuit 5, the switching element is ON / OFF controlled by a control signal corresponding to the inverter main circuit 5, and an AC output is given to the induction motor 7.

When a power failure occurs in the AC power supply, the level of the detection signal from the voltage detection circuit 8 that detects the voltage between the power supply lines 4a and 4b decreases, and the level of the detection signal is the voltage. When the voltage becomes lower than the reference voltage of the level setter 10, the comparator 9 outputs the power failure detection signal Sa. Then, the hold circuit 11 outputs the power failure signal Sb to the PWM signal cutoff circuit 12 so as to maintain the state.
And, the brake device 13 continues to output.

As a result, since the PWM signal from the PWM signal generation circuit 16 is not applied to the inverter main circuit 5, the induction motor 7 is in the free-run state, but is mechanically braked by the brake device 13. Come to a stop.

[0010]

By the way, generally, when the inertial force of the load of the induction motor is large, it takes a considerable time until the rotor of the induction motor is stopped when a power failure occurs. Depending on the situation, it could be dangerous. Therefore, conventionally, in order to cope with such a case, by mounting a mechanical brake on the outside of the induction motor as described above, the sequence is performed so that the induction motor is braked and the rotor is quickly stopped in the event of a power failure. Is being assembled.

However, the provision of the mechanical brake in this way has the drawbacks of increasing the mounting space and increasing the cost, and also in terms of functionality, when the induction motor is rotating at high speed, There was a problem that applying the brakes was dangerous.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an appropriate braking when a power failure occurs and stop the AC motor immediately without installing a mechanical brake outside the AC motor. It is to provide an inverter device that can.

[0013]

According to the present invention, a rectifier circuit for rectifying an input of an AC power source, a smoothing capacitor for smoothing an output of the rectifier circuit, and an AC motor when a control signal is applied to a switching element connected in a bridge. An inverter main circuit for supplying an AC output to the inverter, and a control means for generating a frequency command according to an operation mode pattern selected by a difference between the current frequency command when a target speed command is given and for giving a control signal to the inverter main circuit. And a power failure detecting means for detecting when the input voltage of the AC power supply input drops below a predetermined voltage and outputting a power failure detection signal, and an inverter main unit from the smoothing capacitor. The current detection means for detecting the current flowing through the circuit and the average value of the detected currents of this current detection means are calculated to calculate the current level. A mean value calculating means for outputting as a value signal, and a deceleration for outputting a deceleration time setting signal set so as to shorten the deceleration time as the magnitude of the current mean value signal outputted from the mean value calculating means increases. The control means outputs a power failure detection signal from the power failure detection means, the time setting means and a mode switching means for switching the operation mode pattern to a deceleration mode pattern when the power failure detection signal is output from the power failure detection means. Then, the inverter is configured to follow the deceleration mode pattern switched by the mode switching unit and reduce the rotational speed of the AC electric motor in a deceleration time corresponding to the deceleration time setting signal output from the deceleration time setting unit. It is characterized in that it is configured to give a control signal to the main circuit.

Further, the mode switching means may be configured to switch so as to output the target frequency signal corresponding to the zero frequency as the deceleration mode pattern when the power failure detection signal is output.

The deceleration time setting means may be configured to set the deceleration time in two stages by the comparator according to the magnitude of the current average value signal output from the average value calculating means.

Further, the current detecting means may be configured to detect the input / output current to / from the smoothing capacitor.

[0017]

According to the inverter device of the present invention, in a normal operating condition, the control means generates the frequency command in accordance with the operation mode pattern selected by the difference between the target speed command and the current frequency command, and the inverter is generated. Apply control signals to the main circuit. The inverter main circuit applies an AC output to the AC motor to rotate the AC motor according to the applied control signal.

When a power failure occurs and the AC power supply input drops, the power failure detection means outputs a power failure detection signal. At this time, the deceleration time setting means sets the deceleration time based on the current average value signal of the energizing current flowing from the smoothing capacitor to the inverter main circuit, which is detected by the current detecting means and the average value calculating means, and the control means causes a power failure. Based on the output of the detection signal, the control signal is given to the inverter main circuit in accordance with the deceleration time in the deceleration mode pattern switched and set by the mode switching means.

In this case, the deceleration time setting means is set so that the deceleration time is shortened as the magnitude of the current average value signal output from the average value computing means increases. When current is being supplied to the circuit, that is, when the AC motor is in the power running state due to discharging from the smoothing capacitor, the stronger the power running state, the shorter the deceleration time is set so that the AC motor is braked more strongly. The deceleration control is performed based on the deceleration time setting signal so that the smoothing capacitor is charged.

On the other hand, when a current flows from the inverter main circuit side to the smoothing capacitor side, that is, when the AC motor is in the regenerative state and the smoothing capacitor is charged, the longer the regenerative state, the longer the deceleration time. The terminal voltage of the smoothing capacitor is controlled so as not to become excessive by performing deceleration control based on the deceleration time setting signal.

Therefore, the AC motor can be controlled so as to be held in a regenerative state so that the terminal voltage of the smoothing capacitor is held at a substantially constant value, and the AC main motor can be stopped quickly by driving the inverter main circuit.

According to the inverter device of the second aspect,
When a power failure detection signal is output when a power failure occurs, the mode switching means switches to output the target frequency signal corresponding to the zero frequency as the deceleration mode pattern, so the control means performs the control in the same manner as described above. Even when there is no AC power input in the power failure state, the regenerative power from the AC motor is used to hold the terminal voltage of the smoothing capacitor and drive the inverter main circuit until the AC motor is stopped. The motor can be stopped quickly.

According to the inverter device of the third aspect,
From the result of comparison by the deceleration time setting means according to the magnitude of the current average value signal output from the average value calculating means,
Since the deceleration time is set in two stages, the deceleration time is set so as to shorten the deceleration time when the magnitude of the current average value signal output from the average value calculating means is larger than the comparison value. When current is being supplied from the capacitor side to the inverter main circuit, that is, when the AC electric motor is in the power running state, deceleration control can be performed with a short deceleration time so as to brake the AC electric motor.

On the other hand, when the current is flowing from the inverter main circuit side to the smoothing capacitor side, that is, when the AC motor is in the regenerative state, the deceleration time can be set to a long value and the deceleration can be controlled. However, even if there is no AC power input in the power failure state, regenerative power from the AC motor is used to drive the inverter main circuit while holding the terminal voltage of the smoothing capacitor until the AC motor stops. Then, the AC motor can be stopped quickly.

According to the inverter device of the fourth aspect,
The current detection means detects the input / output current to / from the smoothing capacitor and outputs a current detection signal, and thus detects a current depending on whether the rotating state of the AC motor is in the power running state or the regenerative state when a power failure occurs. You can do the same as above,
Even when there is no AC power input in the power failure state, the regenerative power from the AC motor is used to hold the terminal voltage of the smoothing capacitor and drive the inverter main circuit until the AC motor stops, thereby driving the AC motor. Will be able to stop quickly.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG.
It will be described with reference to FIGS. In FIG. 1 showing an electrical configuration, a three-phase AC power supply 21 is connected to an AC input terminal of a rectification circuit 22 formed by connecting diodes in a bridge connection, and a DC output terminal of the rectification circuit 22 is a DC power supply line 23.
a, 23b. This DC power supply line 23a, 23
b is connected between both terminals of the smoothing capacitor 24 and also connected between the input terminals of the inverter main circuit 25.

The inverter main circuit 25 has a well-known structure in which, for example, six pairs of transistors 25a and diodes 26b as switching elements are bridge-connected,
An induction motor 2 as an AC motor is provided at each of the three-phase output terminals.
6 terminals are connected. A control signal is applied to each transistor 25a of the inverter main circuit 25 as will be described later, and the on / off state of the transistor 25a provides a three-phase AC output having a predetermined frequency to the induction motor 26.

The control circuit 27 as a control means is supplied with power from between the DC power supply lines 23a and 23b (not shown), and is configured to give a control signal to each transistor 25a of the inverter main circuit 25. Has been done. That is, the operation mode setting circuit 28 is adapted to be provided with the target speed command fi, and selects and sets the operation mode pattern from the difference between the frequency command fo currently being output and outputs the operation mode signal. It is connected to a deceleration mode switching circuit 29 as a mode switching means.

The output terminal of the deceleration mode switching circuit 29 is connected to the frequency command output circuit 30. In the normal state, the operation mode signal given from the operation mode setting circuit 28 is output and the power failure signal is output as described later. Is given, a deceleration mode signal is output.

The frequency command output circuit 30 calculates and outputs the frequency command fo on the basis of the operation mode signal given through the deceleration mode switching circuit 29, and its output terminal is the PWM signal generation circuit 31 and the operation mode. It is connected to the setting circuit 28. The PWM signal generation circuit 31 calculates a PWM signal based on the frequency command fo given from the frequency command output circuit 30 and generates a control signal, and its output terminal is sent to the inverter main circuit 25 via the drive circuit 32. It is connected.

The current detector 33 as the current detecting means is
For example, the DC power supply line 23 connected to the inverter main circuit 25 is configured by using a Hall element that is easily insulated.
It is arranged at a and detects the energizing current having a positive value in the direction from the smoothing capacitor 24 side to the inverter main circuit 25 side. The average value calculation circuit 34 as average value calculation means calculates the average value of the detected currents of the current detector 33 and outputs it as a current average value signal, and its output terminal is a deceleration time setting circuit as deceleration time setting means. It is connected to 35.

As shown in FIG. 2, the deceleration time setting circuit 35 is composed of a signal inverting circuit 36 and a bias adding circuit 37. When a current average value signal is given, the signal inverting circuit 36 outputs the current average value. The value signal is inverted, and the bias addition circuit 37 adds a predetermined bias voltage to generate a deceleration time setting signal. The deceleration time setting circuit 35 is connected to the frequency command output circuit 30 via a deceleration time switching circuit 38.

The deceleration time switching circuit 38 gives a signal for setting the deceleration time or acceleration time in the normal mode to the frequency command output circuit 30 in the normal state, and gives it from the deceleration time setting circuit 35 when a power failure signal is given. A deceleration time setting signal is provided.

Power failure detection circuit 39 as power failure detection means
Is connected to the two power supply lines of the three-phase AC power supply 21, detects the power supply voltage falling below a predetermined voltage and outputs a power failure detection signal Sa, the output terminal of which is a hold circuit. It is connected to 40. The hold circuit 40 receives the power failure detection signal Sa and then the power failure signal Sb.
The output terminal is connected to the deceleration mode switching circuit 29 and the deceleration time switching circuit 38.

Next, the operation of this embodiment will be described with reference to FIGS. 3 and 4. That is, when power is normally supplied from the AC power supply 21, the deceleration mode switching circuit 29 is set to the operation mode setting circuit 28 side, and the deceleration time switching circuit 38 is set to the normal mode. . Then, the operation mode setting circuit 28
Compares the target speed command fi with the currently output frequency command fo to determine which mode is acceleration, constant speed or deceleration, and outputs a corresponding operation mode signal.
In this case, the operation mode setting circuit 28 determines that the target speed command f
The relationship between i and the frequency command fo is set to deceleration mode when fi <fo, constant speed mode when fi = fo, and acceleration mode when fi> fo, and the setting signal is output. To do.

The frequency command output circuit 30 calculates the frequency command fo in the operation mode pattern set according to the normal mode deceleration time signal given from the deceleration time switching circuit 38, and outputs it to the PWM signal generation circuit 31. PW
The M signal generation circuit 31 calculates a PWM signal based on the given frequency command fo and outputs it as a control signal, and controls on / off of each transistor 25a of the inverter main circuit 25 via the drive circuit 32 to control the induction motor. I will be driving 26.

Next, when a power failure occurs in the three-phase AC power supply 21, it operates as follows. That is, when the power supply voltage of the three-phase AC power supply 21 drops to a predetermined voltage or lower due to the occurrence of a power failure (see FIG. 4A), the power failure detection circuit 39 outputs the "L" level power failure detection signal Sa. As a result, the hold circuit 40 outputs the power failure signal Sb and holds the output state from that point (see FIG. 11B).

When the power failure signal Sb is output, the deceleration mode switching circuit 29 outputs the deceleration mode signal to the frequency command output circuit 3
The deceleration time switching circuit 38 applies the deceleration time setting signal set by the deceleration time setting circuit 35 to the frequency command output circuit 30 from the normal mode.

In this case, the deceleration time setting circuit 35 generates the deceleration time setting signal as follows. When the energizing current flowing from the smoothing capacitor 24 toward the inverter main circuit 25 is detected by the current detector 33 and the average value calculating circuit 34 outputs the current average value signal (see FIG. 3).
(See (a)), the deceleration time setting circuit 35 inverts the current average value signal (see (b) in the same figure), and decelerates as a signal (see (c) in the same figure) to which a predetermined bias voltage is applied. Generate a signal.

The average current value signal is output from the smoothing capacitor 24 to the inverter main circuit 2 as shown in FIG.
Since the power running of the induction motor 26 is stronger as the value of the current flowing toward 5 increases in the positive direction, the deceleration time is set to be shorter as shown in FIG. On the contrary, when the current average value signal becomes negative, that is, when the current flows from the inverter main circuit 25 side to the smoothing capacitor 24 side, the induction motor 26 is in the regenerative state,
The deceleration time is set to be longer as the regenerative state becomes stronger.

The frequency command output circuit 30 calculates the frequency command fo according to the deceleration time signal set by the deceleration time setting circuit 35 based on the current average value signal (see FIG. 4D). As a result (see FIG. 4E), the regenerative current appropriately flows from the induction motor 26 side to the smoothing capacitor 24, that is, the terminal voltage V of the smoothing capacitor 24 becomes substantially constant (FIG. 4C). (See) to set. Therefore, while the induction motor 26 is kept in the regenerative braking state from the time of the occurrence of the power failure, the terminal voltage of the smoothing capacitor 24 is kept substantially constant to secure the control power supply during that period, and the inverter main circuit 25 The induction motor 26 can be driven to quickly stop.

According to the present embodiment as described above, the deceleration time setting circuit 35 detects the average value of the current flowing through the DC power supply line 23a from the smoothing capacitor 24 to the inverter main circuit 25 to determine its direction and magnitude. According to the induction motor 2
6 is set to shorten the deceleration time when the vehicle is in the power running state and lengthen it when the vehicle is in the regenerative state, and according to the deceleration time output from the deceleration time setting circuit 35 when a power failure occurs, the frequency command output circuit Since the frequency command fo is calculated by 30 and the PWM signal is generated by the PWM signal generation circuit 31 to control the on / off of the inverter main circuit 25, the induction motor 26 is kept in the regenerative braking state from the time when the power failure occurs. However, the terminal voltage of the smoothing capacitor 24 can be maintained at a substantially constant state, a power source for control can be secured during that time, and the induction motor 26 can be stopped quickly.

FIG. 5 shows a second embodiment of the present invention. The difference from the first embodiment is that the deceleration mode switching provided between the operation mode setting circuit 28 and the frequency command output circuit 30 is changed. Instead of the circuit 29, the operation mode setting circuit 2
A mode switching circuit 29a is provided on the input side of 8 as a mode switching means for switching the target speed command fi to the zero speed command fz for output in the event of a power failure.

The mode switching circuit 29a gives the target speed command fi to the operation mode setting circuit 28 in the normal state, and when the hold circuit 40 gives the power failure signal Sb at the time of power failure, the mode switching circuit 29a gives the zero speed command fz to the operation mode setting circuit 28. According to the second embodiment having such a configuration, it is possible to obtain substantially the same operational effect as that of the first embodiment.

FIG. 6 shows a third embodiment of the present invention. The difference from the first embodiment is that the current detector 33 is provided in the path from the smoothing capacitor 24 to the DC power supply line 23a. Also according to the present embodiment as described above, since the energizing current due to the charging / discharging of the smoothing capacitor 24 is detected and the inverter main circuit 25 is drive-controlled according to the detected current, the same effect as the first embodiment is obtained. be able to.

FIGS. 7 and 8 show a fourth embodiment of the present invention. The difference from the first embodiment is that instead of the deceleration time setting circuit 35 and the deceleration time switching circuit 38,
A comparison circuit 41 and a deceleration time switching circuit 42 as deceleration time setting means are provided.

In this case, the comparison circuit 41 includes the comparator 41a.
And a reference voltage setting device 41b. Then, the comparator 41a compares the current average value signal supplied from the average value calculation circuit 34 with the reference voltage supplied from the reference voltage setting unit 41b, and when the current average value signal is large, that is,
When the current flowing from the smoothing capacitor 24 to the inverter main circuit 25 side is large and the induction motor 26 is in a strong power running state, a switching signal is output to switch the setting state of the deceleration time switching circuit 42. The deceleration time switching circuit 42 sets the deceleration time of the normal mode in the normal state. When the switching signal is given from the comparison circuit 41, the deceleration time setting mode is set to a deceleration time shorter than the normal mode and the frequency is set. It is adapted to be given to the command output circuit 30.

When a power failure occurs in the three-phase AC power supply 21 (see FIG. 8A), the power failure detection circuit 39 and the hold circuit 40 output the power failure signal Sb (see FIG. 8B). Similarly to the first embodiment, the frequency command output circuit 30 is set in the deceleration mode.
Then, in this state, when the rotation state of the induction motor 26 is in the power running state, the current average value signal by the current detector 33 and the average value calculation circuit 34 becomes larger than the reference voltage (see (d) of the same figure). A switching signal is output from the comparison circuit 41 (see (e) in the figure).

As a result, the deceleration time switching circuit 42 switches so as to set a short deceleration time, so that the frequency command output circuit 30 follows the frequency command f according to the deceleration time.
o (see (f) in the figure) and outputs the PWM signal generation circuit 3
From 1 to the PWM signal corresponding to the inverter main circuit 25
Will be given to.

On the other hand, when the rotation state of the induction motor 26 is in the regenerative state, the current average value signal becomes smaller than the reference voltage, so the switching signal is not output from the comparison circuit 41, and the deceleration time switching circuit 42 normally operates. Since the switching is performed so as to set the deceleration time in the mode, the frequency command output circuit 30 comes to output the frequency command fo according to the deceleration time.

As a result, the induction motor 26 is maintained in an appropriate regenerative state, that is, the smoothing capacitor 2
The rotation state is controlled so as to keep the terminal voltage of 4 at a substantially constant value (see (c) in the same figure), and while the induction motor 26 is kept in the regenerative braking state from the time when the power failure occurs, The terminal voltage of the smoothing capacitor 24 is maintained at a substantially constant state, a power source for control is secured during that time, and the induction motor 26 can be stopped quickly.
According to the fourth embodiment as described above, it is possible to obtain substantially the same effect as that of the first embodiment, while the deceleration time setting means has a simple configuration with the comparison circuit 41 using the comparator 41a. become.

FIG. 9 shows the fifth embodiment of the present invention. The difference from the fourth embodiment is that the current detector 33 is provided in the path from the smoothing capacitor 24 to the DC power supply line 23a. With this embodiment as well, it is possible to obtain the same effects as those of the fourth embodiment.

[0053]

As described above, according to the inverter device of the present invention, the following effects can be obtained.
That is, according to the inverter device of claim 1, the power failure detecting means detects the power failure of the AC power source, and the deceleration time setting means flows from the smoothing capacitor detected by the current detecting means and the average value calculating means to the inverter main circuit. Based on the current average value signal of the energized current, the deceleration time is shortened as the magnitude of the current average value signal increases, so the current is supplied from the smoothing capacitor side to the inverter main circuit. In other words, when the AC motor is in the power running state, the stronger the power running state, the shorter the deceleration time can be to control the deceleration so that the AC motor is strongly braked. When current is flowing to the capacitor side, that is, when the AC motor is in the regenerative state, the stronger the regenerative state, the slower the speed. Since the deceleration control can be performed by lengthening the interval, the control means outputs the control signal according to the deceleration time in the deceleration mode pattern switched and set by the mode switching means based on the power failure detection signal being output. Even if there is no AC power input during a power failure, the inverter main circuit can be driven while controlling the regenerative power from the AC motor so that the terminal voltage of the smoothing capacitor is almost constant. As a result, the excellent effect that the AC electric motor can be stopped safely and promptly without using a mechanical brake is achieved.

According to the inverter device of the second aspect,
When a power failure detection signal is output when a power failure occurs, the mode switching means switches to output the target frequency signal corresponding to the zero frequency as the deceleration mode pattern, so the control means performs the control in the same manner as described above. Even if there is no AC power input in the power failure state, it is possible to drive the inverter main circuit while controlling the regenerative power from the AC motor so that the terminal voltage of the smoothing capacitor is almost constant. This has an excellent effect that the AC motor can be stopped quickly and safely without using a brake.

According to the inverter device of the third aspect,
From the result of comparison by the deceleration time setting means according to the magnitude of the current average value signal output from the average value calculating means,
Since the deceleration time is set in two stages, the deceleration time is set so as to shorten the deceleration time when the magnitude of the current average value signal output from the average value calculating means is larger than the comparison value. When current is being supplied from the capacitor side to the inverter main circuit, that is, when the AC motor is in the power running state, deceleration can be controlled with a short deceleration time so that the AC motor is braked. When a current is flowing from the side to the smoothing capacitor side, that is, when the AC motor is in the regenerative state, it becomes possible to control the deceleration by setting the deceleration time to a long value. Even when there is no AC power input, the regenerative power from the AC motor is controlled while controlling so that the terminal voltage of the smoothing capacitor is almost constant. It will be able to drive over motor main circuit, an excellent effect of being able to stop quickly or safely and quickly AC motor without using a mechanical brake.

According to the inverter device of the fourth aspect,
The current detection means detects the input / output current to / from the smoothing capacitor and outputs a current detection signal, and thus detects a current depending on whether the rotating state of the AC motor is in the power running state or the regenerative state when a power failure occurs. You can do the same as above,
Even with a simple structure, even if there is no AC power input in the power failure state, it is possible to drive the inverter main circuit while controlling the regenerative power from the AC motor so that the terminal voltage of the smoothing capacitor becomes almost constant. Therefore, it is possible to stop the AC motor quickly and safely and quickly without using a mechanical brake.

[Brief description of drawings]

FIG. 1 is an electrical block diagram showing a first embodiment of the present invention.

FIG. 2 is an electrical block diagram of a deceleration time setting circuit.

FIG. 3 is a correlation diagram of signal conversion in the deceleration time setting circuit corresponding to the value of the current average value signal.

FIG. 4 is a time chart showing a signal output state of each part when a power failure occurs.

FIG. 5 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 6 is a view corresponding to FIG. 1 showing a third embodiment of the present invention.

FIG. 7 is a view corresponding to FIG. 1 showing a fourth embodiment of the present invention.

FIG. 8 is a view corresponding to FIG.

FIG. 9 is a view corresponding to FIG. 1 showing a fifth embodiment of the present invention.

FIG. 10 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

21 is a three-phase AC power supply, 22 is a rectifier circuit, and 23a and 23b.
Is a DC power supply line, 24 is a smoothing capacitor, 25 is an inverter main circuit, 25a is a transistor (switching element), 26 is an induction motor (AC motor), 27 is a control circuit (control means), 28 is an operation mode setting circuit, 29 Is a deceleration mode switching circuit (mode switching means), 29a is a mode switching circuit, 30 is a frequency command output circuit, 31 is a PWM signal generation circuit, 32 is a drive circuit, 33 is a current detector (current detection means), and 34 is an average. A value calculation circuit (mean value calculation means), 35 is a deceleration time setting circuit (deceleration time setting means),
36 is a signal inversion circuit, 37 is a bias addition circuit, 38 is a deceleration time switching circuit, 39 is a power failure detection circuit (power failure detection means), 40 is a hold circuit, 41 is a comparison circuit (deceleration time setting means), and 42 is deceleration time. It is a switching circuit.

Claims (4)

[Claims] 1. A rectifier circuit for rectifying an input of an AC power supply, a smoothing capacitor for smoothing an output of the rectifier circuit, and a switching element, which is bridge-connected to supply an AC output to an AC motor when a control signal is given. An inverter device comprising: a main circuit; and a control means for generating a frequency command according to an operation mode pattern selected by a difference between a current frequency command when a target speed command is given and giving a control signal to the inverter main circuit, A power failure detection means for detecting when the input voltage of the AC power supply input drops below a predetermined voltage and outputting a power failure detection signal, and a current detection means for detecting a current flowing from the smoothing capacitor to the inverter main circuit. An average value calculating means for calculating an average value of the detected currents of the current detecting means and outputting it as a current average value signal And a deceleration time setting means for outputting a deceleration time setting signal set so as to shorten the deceleration time as the magnitude of the current average value signal output from the average value computing means increases, and the power failure detection means And a mode switching means for switching the operation mode pattern to a deceleration mode pattern when the power failure detection signal is output from the control means, when the power failure detection signal is output from the power failure detection means. A control signal is given to the inverter main circuit so as to follow the switched deceleration mode pattern and to decelerate the rotation speed of the AC motor in a deceleration time according to a deceleration time setting signal output from the deceleration time setting means. Characteristic inverter device. 2. The inverter device according to claim 1, wherein the mode switching means switches so as to output a target frequency signal corresponding to a zero frequency as a deceleration mode pattern when the power failure detection signal is output. 3. The deceleration time setting means sets the deceleration time in two steps by a comparator according to the magnitude of the current average value signal output from the average value computing means. Inverter device described. 4. The inverter device according to claim 1, wherein the current detecting means detects an input / output current to / from the smoothing capacitor.