JPH07222436A - Life detection apparatus of smoothing electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain a life detection apparatus in which the proper replacement timing of a smoothing electrolytic capacitor is displayed by a method wherein the ripple voltage or the ripple current, of the smoothing electrolytic capacitor, which is increased with a drop in an electrostatic capacity due to the degradation of the smoothing electrolytic capacitor is detected, the ripple voltage or the ripple current is compared with a preset judgment level and the life of the capacitor is judged. CONSTITUTION:The terminal voltage of a smoothing electrolytic capacitor 4 in a voltage-type inverter device 1 is detected by a voltage detector 6, and the terminal voltage is compared with a life judgment level in a voltage comparator 7. An output is generated only for a period during which the terminal voltage of the smoothing capacitor 4 is less than the life judgment level. In addition, a current which flows in the smoothing electrolytic capacitor 4 is detected by a Hall element 5, it is converted into a DC voltage by a voltage detector 6', and the DC voltage is compared with a life level in a voltage comparator 7'. When a ripple current exceeds the life judgment level, a life detection signal is output. The outputs of the voltage comparators 7, 7' are ANDed with a power-supply condition by respective AND circuits 8, 8', only a life signal is sent to a CPU, and the life of the smoothing electrolytic capacitor is displayed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a life detecting device for a smoothing electrolytic capacitor which smoothes an output DC voltage of a forward conversion circuit which inputs an AC power source and converts it into a DC voltage.

[0002]

2. Description of the Related Art In order to smooth the output DC voltage of a forward conversion circuit in a power conversion device including a forward conversion circuit that inputs an AC power source and converts it into a DC voltage, such as a voltage source inverter device that drives an induction motor. In addition, a relatively large capacity electrolytic capacitor is used. FIG. 5 shows a voltage source inverter.
1 shows a switching device 1, which comprises a forward conversion circuit 2 composed of a diode for rectifying an AC power supply (AC) voltage and converting it into a DC voltage, and a semiconductor switching device such as a GTO converting a DC voltage into an AC voltage. An inverse conversion circuit 3, a smoothing electrolytic capacitor 4 for smoothing the output DC voltage of the forward conversion circuit 2,
A resistor R for suppressing an inrush current when the AC power supply AC is turned on, and a switch M for closing the contacts after the AC power supply AC is turned on.
It is composed of C.

Degradation of characteristics of the smoothing electrolytic capacitor 4 due to aging is an important factor in determining the life of such a voltage source inverter device.

When the voltage source inverter device 1 is operated, a ripple current flows through the smoothing electrolytic capacitor 4 due to the output DC voltage of the forward conversion circuit 2 and the input DC voltage of the inverse conversion circuit 3 is smoothed. As a result, the electrolytic capacitor 4 for smoothing has a property that it causes a temperature rise and its capacitance decreases with the passage of time.

The life of the smoothing electrolytic capacitor 4 is defined by temperature and time, and it is said that the life (usable time) is halved when the temperature rises by about 10 ° C.

[0006]

DISCLOSURE OF THE INVENTION Conventional voltage source inverter
Since the life of the smoothing electrolytic capacitor in the power converter such as a power converter is shorter than that of other parts in the power converter, it is necessary to periodically perform maintenance work to replace only the smoothing electrolytic capacitor.

[0007] Such maintenance work is generally performed every several years with a calculated life that is simulated from the operating conditions of the power converter regardless of the deterioration of the smoothing electrolytic capacitor. Since the calculated life is calculated by taking a safety factor larger than the actual life and replacing it at an early stage, there is a problem that even a product that has not actually been replaced yet is replaced.

The present invention provides a life detecting device for a power conversion device, which displays an appropriate replacement time so that the replacement time of the smoothing electrolytic capacitor is an appropriate replacement time determined by the life of the smoothing electrolytic capacitor. To do.

[0009]

SOLUTION: A detecting means for detecting a ripple voltage or a ripple current of the smoothing electrolytic capacitor which fluctuates with a change in the electrostatic capacitance of the smoothing electrolytic capacitor, and a ripple voltage or a ripple detected by the detecting means. It comprises a comparison means for comparing the current and a predetermined life judgment level and a judgment means for judging the output of the comparison means.

[0010]

With the decrease of the electrostatic capacitance due to the deterioration of the smoothing electrolytic capacitor and the increase of the ripple voltage or the ripple current of the smoothing electrolytic capacitor exceeds the predetermined life judgment level, the output from the comparing means is generated. The time for replacing the smoothing electrolytic capacitor is indicated.

[0011]

The present invention will be described in detail below with reference to its examples.

FIG. 1 shows an embodiment of a life detecting device for a smoothing electrolytic capacitor according to the present invention. A life detecting device for detecting a ripple voltage is a smoothing electrolytic capacitor 4 of a voltage source inverter 1. The voltage detector 6 for detecting the ripple voltage which is the terminal voltage (DC side voltage of the inverter 1), the terminal voltage of the electrolytic capacitor 4 is compared with the life judgment level voltage, and the terminal voltage of the smoothing electrolytic capacitor 4 is It is composed of a voltage comparator 7 that outputs a voltage lower than the life judgment level voltage, and an AND circuit 8 that logically ANDs the output of the voltage comparator 7 and a predetermined measurement condition and outputs the logical product to a CPU (central processing unit). In addition, the life detecting device by detecting the ripple current rectifies the hall element 5 for detecting the ripple current (charge / discharge current) of the smoothing electrolytic capacitor 4 and the output voltage of the hall element 5. A current detector 6'converting into a DC voltage according to the ripple current, and a voltage output when the output voltage of the current detector 6'compared with the life judgment level voltage and the life judgment level voltage. It is composed of a comparator 7'and an AND circuit 8'which takes the logical product of the output of the voltage comparator 7'and a predetermined measurement condition and outputs the logical product to a CPU (central processing unit).

The predetermined measurement condition is a condition in which the ripple voltage or ripple current increases due to causes other than deterioration of the smoothing electrolytic capacitor 4, for example, three-phase AC on the input side of the voltage source inverter device 1. It is an abnormal condition of the AC power supply, such as a power failure, a power failure, or a missing phase of the power supply, and is a measurement condition for accurately determining the replacement time of the smoothing electrolytic capacitor 4.

Next, the operation of the life detecting device shown in FIG. 1 will be described with reference to FIGS.

(1). Life Detection by Ripple Voltage Detection The main circuit DC voltage in the voltage source inverter device 1 is a DC voltage (FIG. 2 (a)) obtained by rectifying the three-phase AC power supply (AC) voltage by the forward conversion circuit 2 and the DC voltage is , The waveform varies depending on the AC load (not shown) of the voltage source inverter device 1. Generally, the waveform (a) is obtained without the smoothing electrolytic capacitor 4, and the waveform (b) is obtained when the smoothing electrolytic capacitor 4 is normal. When the smoothing electrolytic capacitor 4 is deteriorated, the waveform becomes a waveform close to the waveform (a) like the waveform (c). That is, as shown in FIG. 2A, the terminal voltage of the smoothing electrolytic capacitor 4 which is the main circuit DC voltage of the voltage source inverter device 1 includes the ripple voltage, and the smoothing electrolytic capacitor 4 The ripple voltage increases with the deterioration of (reduction of electrostatic capacity), and the fluctuation becomes severe.

The terminal voltage of the smoothing electrolytic capacitor 4 as shown in FIG. 2 (a) is detected by the voltage detector 6 and compared with the life judgment level (FIG. 2 (a-d)) by the voltage comparator 7. The output (FIG. 2B) is generated only while the terminal voltage of the smoothing electrolytic capacitor 4 is below the life judgment level.

The life detection signal (FIG. 2 (b)), which is the output signal of the voltage comparator 7, detects only the deterioration of the smoothing electrolytic capacitor 4, so that the AND operation is performed in the AND circuit 8 with other measurement condition signals. Then, the output of the smoothing electrolytic capacitor 4 is detected by sending the output to a processing device such as a CPU.

(2). About Life Detection by Ripple Current Detection The main circuit DC voltage in the voltage source inverter device 1, that is, the terminal voltage of the smoothing electrolytic capacitor 4 includes the ripple voltage as shown in FIG. 2 (a). A charging / discharging current (ripple current) having the ripple voltage frequency flows through the switch 4.

As shown in FIGS. 2 (c) and 2 (c '), the ripple current flowing in the smoothing electrolytic capacitor 4 is equal to the terminal voltage of the smoothing electrolytic capacitor 4 (FIG. 2 (a-b)). When it falls below the output voltage (FIG. 2 (a-a)) of the forward conversion circuit 2 that rectifies the voltage of the three-phase AC power supply (AC), it flows as a charging current
When it exceeds, it becomes an alternating current that flows as a discharge current, and increases with deterioration of the smoothing electrolytic capacitor 4 (decrease in electrostatic capacity). This ripple current is detected by the Hall element 5, converted into a DC voltage in the current detector 6 ', and compared with the life judgment level in the voltage comparator 7'. When the ripple current exceeds the life judgment level, the life detection signal is output. The AND circuit 8'outputs the logical product with other measurement condition signals and sends the output to a processing device such as a CPU to detect the life of the smoothing electrolytic capacitor 4.

As described above, the predetermined measurement conditions for the AND circuits 8 and 8'in the life detecting device of the above (1) and (2) are, as described above, other than the deterioration of the smoothing electrolytic capacitor 4, the smoothing electrolytic capacitor. No. 4 terminal voltage, a factor that causes fluctuations in charging / discharging current (ripple current), that is, three-phase AC power supply (A
Under conditions such as C) power failure, power supply interruption, or power supply phase loss, by ANDing the life detection signal, which is the output signal of the voltage comparator 7, 7 ', with the AND circuits 8, 8', When the AC power supply (AC) has a power failure, such as a power failure, a phase failure, or a power failure, the life detection signal is sent to a processing device such as a CPU as "interruption", and the life detection is performed only when the smoothing electrolytic capacitor 4 deteriorates. The signal is sent to a processing device such as a CPU so that the life of the smoothing electrolytic capacitor 4 can be accurately displayed.

Hereinafter, the AC power supply (A
The detection of an abnormal power supply state such as a power failure, a phase loss, and a power supply cutoff in C) will be described.

Regarding the power failure and "disconnection" of the AC power supply (AC), the input side AC power supply (A
C) The "open phase" of the AC input power source AC will be described because it can be easily detected depending on the presence or absence of voltage.

FIG. 3 shows an example of the open phase detection circuit. The open phase detection circuit is a voltage type inverter device 1.
(FIG. 1) A three-phase full-wave rectifier circuit 11 using an AC power source (AC) as an input, a filter circuit of a resistor R and a capacitor C, and a filter comparator unit 12 including voltage comparators 13 and 13 '. Has been done.

FIG. 4 shows the operation waveform (a) of the three-phase full-wave rectifier circuit 11 by the three-phase AC power supply (AC) in the open-phase detection circuit shown in FIG. 3, and the DC output of the three-phase full-wave rectifier circuit 11. Voltage,
Terminal voltage waveform of filter capacitor C and voltage comparator
13, 13 'judgment level (b), output of voltage comparator 13, 13' (c,
d) is shown respectively.

The judgment level of the voltage comparator 13 is set higher than the judgment level of the voltage comparator 13 'by the voltage division by the resistors R1, R2, R3, and the level converter
Reference numerals 14 and 14 'are for inputting to the OR (logical sum) circuit 15 with the output levels from both comparators of the voltage comparators 13 and 13' being substantially the same level.

The operation of the open phase detection circuit will be described with reference to FIGS. When the three-phase AC power supply (AC) is normal, the operating voltage waveform of each phase diode (u to z, not shown) of the three-phase full-wave rectifier circuit 11 is as shown by the dotted line in FIG.
The DC output voltage waveform contains a ripple voltage as shown by the dotted line in FIG. 4 (b). The voltage comparator 13 has a resistor R
The DC voltage Cv charged to the maximum value of the DC output voltage is supplied through the filter including the capacitor C and
Although it is compared with the judgment level V1 determined by the voltage dividing resistors R1, R2, R3, its output (FIG. 4 (c)) does not occur because the charging voltage Cv of the capacitor C is higher than the judgment level V1. Further, the DC output voltage (dotted line in FIG. 4 (b)) of the three-phase full-wave rectifier circuit 11 is supplied to the voltage comparator 13 'and compared with the judgment level V2 lower than the judgment level V1. DC voltage Cv
Is higher than the judgment level V2, its output (FIG. 4 (d)) does not occur.

As described above, when the comparison output of the voltage comparators 13 and 13 'does not occur, the open phase output of the open phase detection circuit (FIG. 3) does not occur, and the AND in the life detection circuit (FIG. 1) does not occur.
Signals at the time of normal operation of the three-phase AC power supply AC are supplied to 8, 8 '.

(2). When the three-phase AC power supply (AC) is open-phase Now, assuming that the V-phase of the three-phase AC power supply (AC) is open-phase, each phase diode of the three-phase full-wave rectifier circuit 11 (u to z, not shown) The operating voltage waveform of is as shown by the solid line in FIG. 4 (a), and its DC output voltage includes a large ripple voltage as shown by the solid line in FIG. 4 (b).

The voltage comparator 13 is supplied with the terminal voltage Cv charged in the capacitor C by the DC output voltage of the three-phase full-wave rectifier circuit 11 (solid line in FIG. 4 (b)). Judgment level V1 determined by piezoresistors R1, R2, R3
Compared to. Further, the DC output voltage (solid line in FIG. 4B) of the three-phase full-wave rectification circuit 11 is supplied to the voltage comparator 13 ′ as it is, and the voltage dividers R1, R2, R3 are supplied to the voltage comparator 13 ′.
Is compared with the determination level V2 determined by

In the voltage comparator 13, the terminal voltage Cv of the filter capacitor C supplied is the DC output voltage of the three-phase full-wave rectification circuit 11 due to the open phase of the AC power supply (AC) (see FIG. 4).
Since it gradually decreases with the lapse of time in accordance with the decrease in (b)), the comparison output (FIG. 4 (c)) is generated below the determination level V1 at a certain time t when the open phase state continues.

On the other hand, in the voltage comparator 13 ', the output DC voltage of the supplied three-phase full-wave rectifier circuit 11 (solid line in FIG. 4 (b)).
Is a three-phase AC power supply (AC) twice every cycle
Since it is less than 2, a comparison output (Fig. 4 (d)) is generated each time.

The comparison output signals of the voltage comparators 13 and 13 'are level-adjusted by the level converters 14 and 14', and are generated as the open-phase condition signal of the three-phase AC power supply (AC) via the OR circuit 15. .

According to the above operation of the open-phase detecting circuit, the open-phase detecting circuit allows the three-phase AC power supply (A
It is possible to detect the case where the phase loss of C) continues for a certain period of time or more and the case where it occurs at an instant. By using it as, it is possible to accurately display the replacement time due to deterioration of the smoothing electrolytic capacitor 4.

The open-phase detection circuit sets the open-phase determination level to two levels (V1, V2) and provides two levels of determination, high and low, to determine the instantaneous open-phase and the open-phase that continues for a fixed time. Although two voltage comparators (13, 13 ') are used, the voltage comparator 13 having a high decision level and the filters (R, C) are eliminated and the voltage comparator 13' having a low decision level.
Alternatively, the comparison output (FIG. 4 (d)) may be integrated to generate the open phase detection signal at the time (t) when the predetermined value is reached.

[0035]

As described above, according to the present invention, the following effects can be obtained.

(1). The life of the smoothing electrolytic capacitor
Since it can be detected by quantitative measurement of ripple voltage and ripple current instead of estimation by calculation, the smoothing electrolytic capacitor can be replaced without waste, and proper maintenance is performed and used. It is possible to improve the reliability of a power conversion device such as a voltage source inverter.

(2). Since the measurement conditions for detecting the life of the electrolytic capacitor for smoothing are the AC power supply open phase, power failure, and power supply "off" of the voltage source inverter, those AC power supply open phase, power failure, power supply "off", etc. It is possible to avoid a malfunction that detects the life of the smoothing electrolytic capacitor when the power supply is abnormal, and improve the reliability of the life detecting device.

[Brief description of drawings]

FIG. 1 is an embodiment of a life detecting device for a smoothing electrolytic capacitor according to the present invention.

FIG. 2 is a voltage / current waveform diagram of each part of an embodiment of a life detecting device for a smoothing electrolytic capacitor according to the present invention.

[Figure 3] AC power supply open phase detection circuit

FIG. 4 is a voltage waveform diagram of each part of the open phase detection circuit when the AC power supply has open phase.

FIG. 5: Power conversion device (voltage source inverter device)

[Explanation of symbols]

 1: Voltage source inverter device 2: Forward conversion circuit 3: Reverse conversion circuit 4: Smoothing electrolytic capacitor 5: Current detection hall element 6: Voltage detector 6 ': Current detector 7: Voltage comparator 7 ': Voltage comparator

Claims (4)

[Claims] 1. A smoothing electrolytic capacitor that smoothes a DC output voltage of a forward conversion circuit that inputs an AC power source and converts it into a DC voltage, and a detection circuit that detects a ripple voltage that is a voltage between terminals of the smoothing electrolytic capacitor. A voltage comparator that compares the ripple voltage detected by the detection circuit with a predetermined life judgment level voltage; and a judgment circuit that judges the life of the smoothing electrolytic capacitor based on a comparison output signal of the voltage comparator, An apparatus for detecting the life of a smoothing electrolytic capacitor, characterized by comprising: 2. The discriminating circuit comprises a logical product circuit that obtains a logical product of an abnormal condition signal for detecting an abnormal state of the AC power supply and the comparative output signal.
An apparatus for detecting the life of a smoothing electrolytic capacitor as described above. 3. A smoothing electrolytic capacitor that smoothes a DC output voltage of a forward conversion circuit that inputs an AC power source and converts it into a DC voltage, and a detection circuit that detects a ripple current that is a charging / discharging current of the smoothing electrolytic capacitor. A voltage comparator that compares the ripple current detected by the detection circuit with a predetermined life judgment level current; and a judgment circuit that judges the life of the smoothing electrolytic capacitor based on a comparison output signal of the voltage comparator, An apparatus for detecting the life of a smoothing electrolytic capacitor, characterized by comprising: 4. The smoothing electrolysis according to claim 3, wherein the discrimination circuit comprises a logical product circuit that obtains a logical product of an abnormal condition signal that detects an abnormal state of the AC power supply and the comparison output. Capacitor life detection device.