JPH06311787A - Inverter - Google Patents

Abstract

PURPOSE:To provide an inverter that obtains converted alternating current output at a specified V/F ratio and thus stably operates induction motors if the input supply voltage differs from a rated voltage. CONSTITUTION:If the voltage of an alternating current power supply AC is lower or higher than a rated voltage, the correcting circuit 46 of a control unit 4 corrects frequency control signals F according to the detection output of a supply voltage detecting circuit 6, and obtains a output frequency that attains a rated V/F ratio. If supply voltage exceeds or fall below a rated voltage, output voltage V0 will not exceed or falls below a value determined by a rated V/F ratio, that is, a rated ratio of output voltage to output frequency. This prevents troubles due to the shortage of torque or overcurrent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for V / F control.

[0002]

2. Description of the Related Art Conventionally, an inverter device which performs V / F control using an open loop PWM system has a maximum frequency f.
The maximum voltage Vmax (a voltage that is uniquely determined by the input voltage) is output at max, and the output voltage V ₀ is controlled according to the V / F ratio determined by the maximum frequency fmax and the maximum voltage Vmax at the output frequency f ₀ below that. There is.

[0003]

When the rated voltage of the induction motor used and the AC power supply voltage actually connected to the inverter device as the input power supply do not match in the conventional device as described above, as shown in FIG. when towards the AC power supply voltage is higher than the rated voltage, the same output frequency f becomes higher as compared with the case of the output voltage V ₀ is rated at _0, therefore cause overcurrent abnormality, the operation by acting protection circuit is If it stops, or conversely the AC power supply voltage is lower than the rated voltage,
The output voltage V ₀ is as low as that in the case of the rating, and the induction motor is deficient in torque. Further, there is a problem that a similar phenomenon occurs even when the power supply voltage changes.

The present invention has been made in view of the above problems, and an object thereof is to obtain a converted AC output having a predetermined V / F ratio even when the input power supply voltage is different from the rated voltage. An object of the present invention is to provide an inverter device capable of stably operating an induction motor.

[0005]

According to the invention of claim 1, 3
A power supply voltage detection circuit that detects the voltage of the AC power supply in an inverter device that converts direct current obtained by rectifying and smoothing a phase AC power supply into AC by V / F control and supplies the converted AC output to an induction motor, and the power supply. The control unit controls the converted AC output to have a predetermined V / F ratio according to the detection voltage of the voltage detection circuit.

According to a second aspect of the invention, in the first aspect of the invention, the voltage of the converted AC output is corrected based on a predetermined V / F ratio according to the detection voltage of the power supply voltage detection circuit. . According to the invention of claim 3, in the invention of claim 1, according to the detection voltage of the power supply voltage detection circuit,
The frequency of the converted AC output is corrected based on a predetermined V / F ratio.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the power supply voltage detection circuit operates by using the direct current as a power supply and supplies a stabilized output to the control unit as a power supply. The AC power supply voltage is detected from the voltage of the stabilized output.

[0008]

According to the first aspect of the present invention, even if the AC power source voltage as the input power source deviates from the rated voltage, the converted AC output can be corrected in accordance with a predetermined V / F ratio, and therefore, the induction as a load. The electric motor can be operated stably.
According to the second aspect of the present invention, even if the AC power source voltage as the input power source deviates from the rated voltage, the voltage of the converted AC output is corrected to a voltage based on the V / F ratio. Trouble can be avoided.

According to the invention of claim 3, since the frequency of the converted AC output is corrected to the frequency based on the V / F ratio even if the AC power supply voltage as the input power supply deviates from the rated voltage, the torque compensation of the induction motor is performed. Can be done. According to the invention of claim 4, there is no need to use an AC transformer that is costly and large in size, and there is no trouble at the time of phase loss, and the AC power supply voltage is reliably insulated from the AC power supply. Can be detected.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a circuit of this embodiment, in which a three-phase AC power supply AC is rectified by a rectifier circuit 1 and smoothed by a smoothing capacitor C ₁ , and three DCs obtained by this smoothing are paired. The output circuit 2 in which the switching elements of the above are connected in a bridge form is converted into an alternating current of a predetermined frequency, and this converted alternating current output is converted into an induction motor M.
It is designed to be supplied to. The control unit 4 is for driving the switching element of the output circuit 2 by the PWM method through the driver 3, and accelerates so as to reach the frequency set by the frequency setting unit 5 in a predetermined time when accelerating or decelerating. Alternatively, the acceleration / deceleration limiting circuit 41 for limiting the deceleration and the acceleration / deceleration limiting circuit 41
Receiving a signal from the output voltage V ₀ is a voltage control signal V which determines the output voltage V ₀ so that the voltage of the predetermined V / F ratio when the output frequency f ₀ reaches the set frequency, the output frequency f V / F that outputs a frequency control signal F that determines ₀
A converter 42 and a voltage control circuit 43 that receives the voltage control signal V from the V / F converter 42 and determines an output voltage V _0.
A frequency control circuit 44 that receives the frequency control signal F to determine the output frequency f ₀ , and these frequency control circuits 44,
Upon receiving the signal from the voltage control circuit 43, a predetermined output frequency f ₀
PWM with which an AC output of a predetermined output voltage V ₀ can be obtained
A PWM signal synthesizing circuit 45 for creating a signal and a correction circuit 46 for receiving the detection signal of the external power supply voltage detection circuit 6 and correcting the frequency control signal F are provided.

The power supply voltage detection circuit 6 detects the voltage of the AC power supply AC from the DC voltage supplied to the output circuit 2, and its voltage detection input terminal is connected to both ends of the smoothing capacitor C ₁ . Specifically, as shown in FIG.
To the input side of the regulator 8 provided on the output side of the DC-DC converter 7 that supplies power for control operation, that is, the negative voltage of the unstabilized output proportional to the voltage of the AC power supply AC The difference voltage ± ΔV with respect to the reference voltage set corresponding to is detected, and this difference voltage ± ΔV is output to the correction circuit 46 as the correction value of the frequency control signal F.

The DC-DC converter 7 is a smoothing capacitor.
C₁DC power source smoothed by
Oscillation transformer T
Feedback winding n₃Switch output through driver 7a
This is given to the base of Ng Transiter Q and turned on and off.
The secondary winding n of the oscillation transformer T is turned on and off.₂One on the side
Next winding n₁A high frequency voltage corresponding to the winding ratio of
This voltage is rectified and smoothed to return to direct current.
Of the DC voltage of the regulator 8 as shown in FIG. ₁Cheap
This stabilized direct current is supplied to the control unit 4 as an operating power source.
And then supply it. In addition, the power supply voltage detection circuit
The voltage input to 6 is the voltage that is obtained by rectifying and smoothing the secondary output.
Therefore, the voltage Vs of the input power supply, that is, the AC power supply AC
Voltage V proportional to₂Becomes

When the voltage Vs of the AC power supply AC is lower than the rated voltage, the difference voltage ΔV detected by the power supply voltage detection circuit 6 is on the negative side, and the control unit is in accordance with this difference voltage ΔV. The correction circuit 46 of No. 4 corrects the frequency control signal F so that the output frequency f ₀ corresponds to the output voltage V ₀ determined by the rated V / F ratio. That same output frequency f ₀ as when the power supply voltage Vs is low shown in FIG. 4 (a)
The output voltage V ₀ is was low as compared with the case at the rated for a power supply voltage detection circuit in the present embodiment 6
The correction circuit 46 of the control unit 4 corrects the frequency control signal F in order to obtain the output frequency f ₀ that provides the rated V / F ratio in accordance with the detected output ΔV. As a result, the output voltage V ₀ and the output frequency f ₀ according to the V / F ratio in the rated case can be obtained, and the torque shortage can be avoided.

On the other hand, when the voltage Vs of the AC power supply AC is higher than the rated voltage, the difference voltage ΔV detected by the power supply voltage detection circuit 6 is on the + side, and the control section 4 of the control unit 4 responds to this difference voltage ΔV. The correction circuit 46 corrects the frequency control signal F so that the output frequency f ₀ corresponds to the output voltage V ₀ determined by the rated V / F ratio. As a result, the power supply voltage Vs
4 is high, the output voltage V _{0 with} respect to the same output frequency f ₀ is as shown in FIG.
Although it is as high as in the conventional case, in the present embodiment, the frequency control signal F is set so that the correction circuit 46 of the control unit 4 has the V / F ratio in the case of the rating according to the detection output ΔV of the power supply voltage detection circuit 6. Is corrected. Therefore, the output frequency f
_With respect to ₀ , the output voltage V ₀ does not exceed the voltage determined by the rated V / F ratio, so that trouble due to overcurrent abnormality can be avoided.

(Embodiment 2) The above-mentioned Embodiment 1 has a power supply voltage Vs.
Output voltage f ₀Set
The correction is performed so that the V / F ratio is as high as possible.
In this embodiment, the output voltage V₀To be the rated V / F ratio
The correction is made to. FIG. 5 shows the circuit configuration of this embodiment.
It is shown according to the detection output ΔV of the power supply voltage detection circuit 6.
The correction circuit 46 includes a voltage control circuit 43 and a V / F converter 42.
The voltage control signal V given by
There is. The configuration of the power supply voltage detection circuit 6 is similar to that of the first embodiment.
Use

Thus, the voltage Vs of the AC power supply AC is the rated voltage
If it is lower than, it is detected by the power supply voltage detection circuit 6.
The differential voltage ΔV becomes negative and the voltage is controlled in accordance with this differential voltage ΔV.
The correction circuit 46 of the control unit 4 is determined by the V / F ratio at the time of rating.
Output frequency f₀Output voltage V₀Will be
The voltage control signal V is corrected as described above. That is, the power supply voltage Vs
When it is low, the same output voltage V as shown in FIG.₀
Output frequency f ₀Is the conventional case compared to the rated case
However, in this embodiment, the power supply voltage
According to the detection output ΔV of the detection circuit 6, the rated V / F ratio and
Output voltage V ₀The voltage control signal V to obtain
It is.

On the other hand, when the voltage Vs of the AC power supply AC is higher than the rated voltage, the difference voltage ΔV detected by the power supply voltage detection circuit 6 is on the + side, and the control section 4 of the controller 4 responds to this difference voltage ΔV. The correction circuit 46 corrects the voltage control signal V so that the output voltage V ₀ corresponds to the output frequency f ₀ defined by the rated V / F ratio. That is, when the power supply voltage Vs is high, as shown in FIG. 4B, the output frequency f ₀ for the same output voltage V ₀ is higher as in the conventional case as compared with the rated _value , but in the present embodiment, The correction circuit 46 of the control unit 4 corrects the voltage control signal V in order to obtain the output voltage V ₀ which becomes the rated V / F ratio according to the detection output ΔV of the power supply voltage detection circuit 6.

In this way, in this embodiment, the output frequency f ₀ and the output voltage V ₀ having the V / F ratio corresponding to the rating can be obtained, so that a constant torque can be obtained and the torque can be compensated.

[0019]

According to the first aspect of the present invention, in the inverter device for converting the direct current obtained by rectifying and smoothing the alternating current power source into the alternating current by the V / F control and supplying the converted alternating current output to the induction motor, the voltage of the alternating current power source is changed. Since the power supply voltage detection circuit for detection and the control unit for controlling the converted AC output to have a predetermined V / F ratio in accordance with the detection voltage of the power supply voltage detection circuit are provided, an AC power supply that is an input power supply is provided. Even if the power supply voltage deviates from the rated voltage, the converted AC output is a predetermined V / F
It is possible to perform correction according to the ratio, and as a result, it is possible to stably operate the induction motor that is a load.

According to a second aspect of the present invention, the voltage of the converted AC output is corrected based on a predetermined V / F ratio according to the detection voltage of the power supply voltage detection circuit. Since the voltage of the converted AC output is corrected to a voltage based on the V / F ratio even when the voltage deviates from the rated voltage, it is possible to avoid troubles such as excessive current abnormality and insufficient torque.

According to a third aspect of the present invention, the frequency of the converted AC output is corrected based on a predetermined V / F ratio according to the detection voltage of the power supply voltage detection circuit. Even if it deviates from the rated voltage, the frequency of the converted AC output is corrected to the frequency based on the V / F ratio.
There is an effect that the torque of the induction motor can be compensated.

According to a fourth aspect of the present invention, the power supply voltage detection circuit operates by using the direct current as a power supply and supplies the stabilized output to the control unit as a power supply from the voltage of the unstabilized output of the DC-DC converter. Since it detects the AC power supply voltage,
There is no need to use an AC transformer that is costly and large, and there is an effect that the AC power supply voltage can be reliably detected while the AC power supply voltage is insulated from the AC power supply without any trouble at the time of phase loss. .

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram showing a specific configuration of a main part of the above.

FIG. 3 is an explanatory diagram of an operation of the above power supply voltage detection circuit.

FIG. 4 is an explanatory diagram of an output frequency correction operation of the above.

FIG. 5 is a circuit configuration diagram of a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of an output voltage correction operation of the above.

FIG. 7 is an operation explanatory diagram of a conventional example.

[Explanation of symbols]

AC AC power supply C ₁ Smoothing capacitor M Induction motor 1 Rectifier circuit 2 Output circuit 3 Driver 4 Control unit 5 Frequency setting unit 6 Power supply voltage detection circuit 41 Acceleration / deceleration limiting circuit 42 V / F converter 43 Voltage control circuit 44 Frequency control circuit 45 PWM signal synthesis circuit 46 Correction circuit V voltage control signal F frequency control signal

Front page continued (72) Inventor Tomoaki Izumimoto 1048, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works Ltd. (72) Inventor Hiroshi Mizuno 1048, Kadoma, Kadoma City, Osaka Matsushita Electric Works Ltd. Inventor Ichiro Tatezawa 1048, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (4)

[Claims] 1. A power supply voltage detection circuit for detecting a voltage of the AC power supply in an inverter device for converting a direct current obtained by rectifying and smoothing an AC power supply into an AC by V / F control and supplying the converted AC output to an induction motor. , A predetermined V of the conversion AC output according to the detection voltage of the power supply voltage detection circuit
An inverter device, comprising: a control unit that controls the F / F ratio. 2. According to the detection voltage of the power supply voltage detection circuit,
The inverter device according to claim 1, wherein the voltage of the converted AC output is corrected based on a predetermined V / F ratio. 3. According to the detection voltage of the power supply voltage detection circuit,
The inverter device according to claim 1, wherein the frequency of the converted AC output is corrected based on a predetermined V / F ratio. 4. The power supply voltage detection circuit detects the AC power supply voltage from a voltage of an unstabilized output of a DC-DC converter which operates by using the direct current as a power supply and supplies a stabilized output to a control unit as a power supply. Claim 1 characterized by the above.
Inverter device described.