JP3775053B2 - Inverter device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an open phase detection means on the input side of an inverter device.
[0002]
[Prior art]
FIG. 3 is a circuit configuration diagram showing a conventional example of this type of inverter device. 1 is a three-phase AC power source such as a commercial power source, 2 is a circuit breaker, 3 is an inverter device, and 4 is a load of the inverter device 3. This is an electric motor.
The inverter device 3 shown in FIG. 3 includes, for example, a rectifier circuit 31 formed by connecting a diode in a three-phase bridge, an electrolytic capacitor 32 as a smoothing capacitor, and six switching circuits in which a transistor and a diode are connected in antiparallel. An inverter 33 formed by a three-phase bridge connection, a control circuit 34 for controlling the output of the inverter 33 to a three-phase AC voltage having a desired voltage and frequency, and an open-phase relay 35 are provided.
[0003]
When the three-phase AC power source 1 is missing any phase for some reason, the phase loss relay 35 detects this and sends a phase loss signal to the control circuit 34. The operation is stopped to prevent, for example, overheating burnout and deterioration of the electrolytic capacitor 32 due to the above state, and this stop is displayed outside the inverter device 3.
[0004]
[Problems to be solved by the invention]
A commercially available open phase relay 35 manufactured by a well-known technology that constitutes the conventional inverter device 3 is relatively expensive and requires a lot of installation space, which is a factor that hinders downsizing and cost reduction of the inverter device. .
An object of the present invention is to provide a small and inexpensive inverter device that solves the above problems.
[0005]
[Means for Solving the Problems]
The first aspect of the present invention is an inverter device for converting a DC voltage obtained from a multiphase AC power source through a rectifier circuit and a smoothing capacitor into an AC voltage having a desired voltage and frequency by an inverter and feeding the load to a load.
A band-pass filter that extracts a ripple component having a frequency twice the fundamental frequency of the AC power source included in the DC voltage, an effective value calculation circuit that calculates and outputs an effective value of the output of the band-pass filter, and an effective value calculation And a comparison circuit that outputs an open phase signal to the outside when the output value of the circuit becomes a predetermined value or more.
[0006]
Moreover, 2nd invention is the said inverter apparatus,
A band-pass filter that extracts a ripple component having a frequency twice the fundamental frequency of the AC power source included in the DC voltage, an effective value calculation circuit that calculates and outputs an effective value of the output of the band-pass filter, and an effective value calculation A square value calculation circuit that calculates and outputs the square value of the output value of the circuit, a first-order lag filter that outputs a value through a first-order lag filter to the output of the square value calculation circuit, and an output value of the first-order lag filter And a comparison circuit for outputting an open phase signal to the outside when the value becomes equal to or greater than a predetermined value.
[0007]
According to this invention, in place of the phase loss relay provided in the conventional inverter device, by providing a new phase loss detection means formed by the above-described circuit or the like, digital control of the inverter device by a microcomputer in particular in recent years. In this case, as will be described later, the phase loss detection means can be easily realized by this digital control, which can contribute to downsizing and cost reduction of the apparatus.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a circuit configuration diagram of an inverter device showing a first embodiment of the present invention. Components having the same functions as those of the conventional circuit shown in FIG. 3 are denoted by the same reference numerals.
That is, in the inverter device 5 shown in FIG. 1, in addition to the rectifier circuit 31, the electrolytic capacitor 32, the inverter 33, and the control circuit 34, a voltage detector 51 that detects the voltage across the electrolytic capacitor 32, a band-pass filter 52, An effective value calculation circuit 53 and a comparison circuit 54 are provided.
[0009]
The voltage detector 51 shown in FIG. 1 detects, for example, that the voltage across the electrolytic capacitor 32 has risen to a specified value or more by regenerative power from the motor 4, and operates a resistance discharge circuit (not shown) that suppresses this rise. Can be shared with other voltage detectors.
In addition, when the inverter device 5 is in a normal operation state, the voltage across the electrolytic capacitor 32 mainly includes a ripple component having a frequency six times the basic frequency of the three-phase AC power source 1, but rectified from the three-phase AC power source 1. When some trouble occurs in the path to the output of the circuit 31 and any phase is missing, the voltage across the electrolytic capacitor 32 has a ripple component having a frequency twice the basic frequency of the three-phase AC power supply 1. Is known to increase.
[0010]
Therefore, the band-pass filter 52 may be a band-pass filter having a band of, for example, 100 Hz to 120 Hz in order to pass only a ripple component having a frequency twice the basic frequency (50 Hz or 60 Hz) of the three-phase AC power supply 1.
When the function of the band pass filter 52 is performed using a microcomputer, the detected value of the voltage across the electrolytic capacitor 32 is converted every sampling period (T _S ) by an A / D converter added to the voltage detector 51. The obtained digital value is obtained, and a frequency component twice the fundamental frequency of the three-phase AC power supply 1 can be extracted by passing the digital value through a known band-pass digital filter.
[0011]
Next, the effective value calculation circuit 53 obtains an effective value of a ripple component having a frequency twice the basic frequency of the three-phase AC power supply 1 extracted by the band pass filter 52. At this time, when using a microcomputer, the following arithmetic expression is calculated from the digital value of the ripple component extracted by the band pass filter 52.
[0012]
[Expression 1]
v _RMS = {(1 / T) (v _{P (1)} ² + v _{P (2)} ² + ·· + v _{P (N)} ² )} ^1/2 (1)
Here, v _RMS represents an effective value of the ripple component, v _{P (K)} : K (K = 1 · 2... N) -th output value of the bandpass filter 52, and T = T _S · N There is a relationship.
Further, in the comparison circuit 54, when the output value (v _RMS ) at each time T of the effective value calculation circuit 53 exceeds a predetermined value, there is some problem in the path from the three-phase AC power supply 1 to the output of the rectifier circuit 31. If any of the phases is generated, an open phase signal is output, and the operation of the control circuit 34 is stopped by the open phase signal, for example, the electrolytic capacitor 32 caused by the above state. Overheating burnout and deterioration are prevented, and this stop is displayed outside the inverter device 5.
[0013]
When the function of the band pass filter 52 and the function of the effective value calculation circuit 53 are performed using a microcomputer, the digital value converted at every sampling period (T _S ) of the detected value of the voltage across the electrolytic capacitor 32. Thus, the effective value of the ripple component having a frequency twice the fundamental frequency of the three-phase AC power supply 1 can be directly obtained by a known discrete Fourier transform method.
[0014]
FIG. 2 is a circuit configuration diagram of an inverter device showing a second embodiment of the present invention. Components having the same functions as those of the embodiment circuit shown in FIG.
That is, the inverter device 6 shown in FIG. 2 includes the rectifier circuit 31, the electrolytic capacitor 32, the inverter 33, the control circuit 34, the voltage detector 51, the band pass filter 52, the effective value calculation circuit 53, and the comparison circuit 54. A square value calculation circuit 61 and a first-order lag filter 62 are inserted in the path from the value calculation circuit 53 to the comparison circuit 54.
[0015]
In FIG. 2, the calculation function of the above-described effective value calculation circuit 53 and the calculation function of the square value calculation circuit 61 for obtaining the square value of the output of the effective value calculation circuit 53 can be processed simultaneously. Performs the following arithmetic expression.
[0016]
[Expression 2]
v _RMS ² = (1 / T) (v _{P (1)} ² + v _{P (2)} ² + ·· + v _{P (N)} ² ) (2)
In the first-order lag filter 62, the time constant of this filter is set to be approximately equal to the thermal time constant of the electrolytic capacitor 32.
That is, the comparator circuit 54 is operated when the output value of the first-order lag filter 62 exceeds a predetermined value, and the comparator circuit 54 outputs an open phase signal, and the operation of the control circuit 34 is stopped by this open phase signal. Then, the electrolytic capacitor 32 is prevented from being overheated and deteriorated due to the above state, and this stop is displayed outside the inverter device 6.
[0017]
【The invention's effect】
According to the present invention, the phase loss detection means formed by the above-described arithmetic circuit, filter, etc. can be easily implemented especially by digital control by a microcomputer, and a voltage detector necessary for the operation of the above-described resistance discharge circuit, and this If the voltage detector of the invention is shared, it is not necessary to add a new hardware circuit to the inverter device. As a result, the device can be reduced in size and cost.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of an inverter device according to a first embodiment of the present invention. FIG. 2 is a circuit configuration diagram of an inverter device according to a second embodiment of the present invention. Circuit configuration diagram [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Three-phase alternating current power supply, 2 ... Circuit breaker, 3 ... Inverter device, 4 ... Electric motor, 5, 6 ... Inverter device, 31 ... Rectifier circuit, 32 ... Electrolytic capacitor, 33 ... Inverter, 34 ... Control circuit, 35 ... Phase loss relays 35, 51 ... voltage detector, 52 ... band pass filter, 53 ... effective value calculation circuit, 54 ... comparison circuit, 61 ... square value calculation circuit, 62 ... primary delay filter.

Claims (2)

In an inverter device that converts a DC voltage obtained from a polyphase AC power source through a rectifier circuit and a smoothing capacitor into an AC voltage of a desired voltage and frequency by an inverter and supplies power to a load.
A band-pass filter that extracts a ripple component having a frequency twice the fundamental frequency of the AC power source included in the DC voltage;
An effective value calculation circuit for calculating and outputting the effective value of the output of the bandpass filter;
An inverter device comprising: a comparator circuit that outputs an open phase signal to the outside when an output value of an effective value arithmetic circuit becomes a predetermined value or more. In an inverter device that converts a DC voltage obtained from a polyphase AC power source through a rectifier circuit and a smoothing capacitor into an AC voltage of a desired voltage and frequency by an inverter and supplies power to a load.
A band-pass filter that extracts a ripple component having a frequency twice the fundamental frequency of the AC power source included in the DC voltage;
An effective value calculation circuit for calculating and outputting the effective value of the output of the bandpass filter;
A square value calculation circuit for calculating and outputting the square value of the output value of the effective value calculation circuit;
A first-order lag filter that outputs a value through a first-order lag filter to the output of the square value arithmetic circuit;
An inverter device comprising: a comparison circuit that outputs an open phase signal to the outside when the output value of the first-order lag filter exceeds a predetermined value.

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