Power conversion device

Abstract

To prolong the total lifetime of a plurality of aluminum electrolytic capacitors constituting a power conversion device.SOLUTION: A power conversion device comprises a power semiconductor element 1, control means which controls a switching operation of the power semiconductor element 1, and a printed circuit board 4 on which a plurality of aluminum electrolytic capacitors 3 is mounted. The control means estimates the remaining lifetime of the aluminum electrolytic capacitor 3 from an ambient temperature and the time of use of the aluminum electrolytic capacitor 3 and, when the estimated remaining lifetime reaches a reference, causes a notification section to perform a notification. A first external terminal 5a and a second external terminal 5b for connecting the power semiconductor element 1 are provided on the printed circuit board 4. A positional relation between the plurality of aluminum electrolytic capacitors 3 and the power semiconductor element 1 changes between a state where the power semiconductor element 1 is connected to the first external terminal 5a and a state where the power semiconductor element 1 is connected to the second external terminal 5b.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a power conversion device. [Background technology]

[0002] Capacitors used in power conversion devices deteriorate with use, and therefore users must take measures such as replacing them. As a technology to support user actions, for example, Patent Document 1 discloses a technology that notifies users of the lifespan of capacitors used in power conversion devices. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-289752 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, a power semiconductor device that supplies AC power to an electric motor used in an elevator or escalator is connected to a printed circuit board on which multiple aluminum electrolytic capacitors are mounted. In this case, a larger current flows through the aluminum electrolytic capacitor located closer to the power semiconductor device than through the other aluminum electrolytic capacitors. Aluminum electrolytic capacitors located closer to the power semiconductor device generate more heat during use, deteriorating more easily than other aluminum electrolytic capacitors and having a shorter lifespan. Conventionally, it has been necessary to replace the entire printed circuit board in accordance with the aluminum electrolytic capacitor that deteriorates the fastest. Conventionally, the total lifespan of multiple aluminum electrolytic capacitors mounted on a printed circuit board is determined by the lifespan of the aluminum electrolytic capacitor that deteriorates the fastest.

[0005] The present disclosure is intended to solve the above-mentioned problems, and an object of the present disclosure is to extend the total life of a plurality of aluminum electrolytic capacitors that constitute a power conversion device. [Means for solving the problem]

[0006] A power conversion device according to the present disclosure includes a power semiconductor element that converts input DC power into AC power and supplies the AC power to an electric motor, a control unit that controls the switching operation of the power semiconductor element, multiple aluminum electrolytic capacitors that are disposed between the positive and negative poles of the DC power, and a printed circuit board on which the multiple aluminum electrolytic capacitors are mounted. The control unit estimates the remaining life of the aluminum electrolytic capacitors based on the ambient temperature and usage time of the aluminum electrolytic capacitors, and causes a notification unit to issue a notification when the estimated remaining life reaches a reference value. The printed circuit board is provided with first external terminals for connecting the power semiconductor elements and second external terminals that are different from the first external terminals. The positional relationship between the multiple aluminum electrolytic capacitors and the power semiconductor elements changes depending on whether the power semiconductor elements are connected to the first external terminals or the second external terminals. [Effects of the Invention]

[0007] According to the present disclosure, the total life of the multiple aluminum electrolytic capacitors that make up a power conversion device can be extended. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing an overall configuration of a power conversion device according to a first embodiment. [Figure 2] 2 is a diagram showing an example of the external shapes of a power semiconductor element and a printed circuit board that configure the power conversion device of the first embodiment. FIG. [Figure 3] FIG. 10 is a diagram illustrating a first modified example of the first embodiment. [Figure 4] FIG. 10 is a diagram illustrating a second modification of the first embodiment. [Figure 5]FIG. 3 is a diagram showing an example of observation by a temperature sensor in the first embodiment. [Figure 6] FIG. 3 is a diagram for explaining a method for determining the remaining lifetimes of a plurality of aluminum electrolytic capacitors in the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of a power conversion device according to the present disclosure will be described with reference to the accompanying drawings. The same reference numerals in the various drawings indicate the same or corresponding parts. In this disclosure, redundant descriptions will be appropriately simplified or omitted. Note that the present disclosure is not limited to the embodiments described below, and may include any combinations and modifications of the configurations disclosed in the following embodiments.

[0010] Embodiment 1 Fig. 1 is a diagram showing the overall configuration of a power conversion device according to embodiment 1. As shown in Fig. 1, the power conversion device according to the present embodiment includes a power semiconductor element 1, a control unit 2, a plurality of aluminum electrolytic capacitors 3, and a printed circuit board 4.

[0011] The power semiconductor element 1 is a device that performs power conversion through switching operation. The power semiconductor element 1 converts input DC power into AC power. The power semiconductor element 1 supplies the converted AC power to the electric motor 10. The control unit 2 controls the switching operation of the power semiconductor element 1. By controlling the switching operation of the power semiconductor element 1 by the control unit 2, the DC power is converted into the desired AC power and input to the electric motor 10.

[0012] The plurality of aluminum electrolytic capacitors 3 are arranged between the positive and negative poles of the DC power input to the power semiconductor element 1. The plurality of aluminum electrolytic capacitors 3 are arranged in parallel or in series. The printed circuit board 4 is a board on which the plurality of aluminum electrolytic capacitors 3 are mounted. The printed circuit board 4 is provided with wiring that connects the positive poles and negative poles of the plurality of aluminum electrolytic capacitors 3 to each other. DC power is input to the power semiconductor element 1 from the printed circuit board 4 on which the aluminum electrolytic capacitors 3 are mounted.

[0013] 1, the power conversion device of this embodiment also includes a temperature measurement unit 6. The temperature measurement unit 6 measures the ambient temperature of the aluminum electrolytic capacitor 3. The temperature measurement unit 6 is configured, for example, by a thermistor or the like provided near the power semiconductor element 1.

[0014] The life of the aluminum electrolytic capacitor 3 depends on temperature. For example, the life of the aluminum electrolytic capacitor 3 becomes shorter as the temperature of the usage environment increases or as the internal temperature increases due to self-heating during use. The remaining life of the aluminum electrolytic capacitor 3 can be estimated based on the ambient temperature of the aluminum electrolytic capacitor 3 and the usage time of the aluminum electrolytic capacitor 3. The control unit 2 of this embodiment estimates the remaining life of the aluminum electrolytic capacitor 3 from the ambient temperature and usage time of the aluminum electrolytic capacitor 3. The control unit 2 and temperature measurement unit 6 of this embodiment constitute an example of a control means according to the present disclosure.

[0015] For example, the aluminum electrolytic capacitor 3 deteriorates due to the current flowing therethrough caused by the switching operation of the power semiconductor element 1. Furthermore, even when no current is flowing through the aluminum electrolytic capacitor 3, the aluminum electrolytic capacitor 3 deteriorates due to the ambient temperature. In this disclosure, the usage time of the aluminum electrolytic capacitor 3 corresponds to the time the power conversion device is in use, i.e., the time the power conversion device is turned on or the time current is flowing to the power conversion device.

[0016] When the estimated remaining life reaches a standard, the control unit 2 causes the notification unit 7 to issue a notification. The notification method by the notification unit 7 may be any method, such as notification by sound, light, or screen display. By issuing a notification by the notification unit 7, the user can easily confirm that the remaining life of the aluminum electrolytic capacitor 3 has reached the standard.

[0017] FIG. 2 is a diagram showing an example of the external shapes of the power semiconductor elements 1 and the printed circuit board 4 that constitute the power conversion device of the first embodiment. As described above, a plurality of aluminum electrolytic capacitors 3 are mounted on the printed circuit board 4. As shown in FIGS. 1 and 2, the printed circuit board 4 is provided with a plurality of external terminals 5 for connecting the power semiconductor elements 1. The positive and negative electrodes of the aluminum electrolytic capacitors 3 are connected to the power semiconductor elements 1 via the external terminals 5. As an example, the plurality of external terminals 5 include a first external terminal 5a and a second external terminal 5b that is different from the first external terminal 5a. The number of external terminals 5 is not limited to two and may be any number equal to or greater than two.

[0018] In the example shown in FIG. 2, the printed circuit board 4 is directly connected to the power semiconductor element 1. For example, the first external terminal 5a of the printed circuit board 4 is configured as a land that can be screwed to an input terminal of the power semiconductor element 1. Like the first external terminal 5a, the second external terminal 5b may also be configured as a land that can be screwed to an input terminal of the power semiconductor element 1. In this example, a member such as a bus bar for connecting the power semiconductor element 1 and the printed circuit board 4 is not required. Note that the power semiconductor element 1 and the printed circuit board 4 may also be indirectly connected via a member such as a bus bar.

[0019] 2, the power semiconductor element 1 is connected to the first external terminal 5a. From this state, the printed circuit board 4 can be rotated 180 degrees to connect the power semiconductor element 1 to the second external terminal 5b. The positional relationship between the multiple aluminum electrolytic capacitors 3 and the power semiconductor element 1 changes depending on whether the power semiconductor element 1 is connected to the first external terminal 5a or the second external terminal 5b.

[0020] For example, when the power conversion device is used in the state shown in FIG. 2 and the remaining life of the aluminum electrolytic capacitor 3 arranged near the power semiconductor element 1 reaches a reference value, the notification unit 7 issues a notification. Upon receiving this notification, the user rotates the printed circuit board 4 by 180 degrees and connects the power semiconductor element 1 to the second external terminal 5b. This changes the aluminum electrolytic capacitor 3 arranged near the power semiconductor element 1, allowing the printed circuit board 4 to continue to be used. According to this embodiment, the printed circuit board 4 can be used for a longer period of time, thereby lengthening the total life of the multiple aluminum electrolytic capacitors 3 that make up the power conversion device.

[0021] The positional relationship between the power semiconductor element 1 and the printed circuit board 4 may be horizontal as shown in FIG. 2(a) or vertical as shown in FIG. 2(b).

[0022] Fig. 3 is a diagram showing a first modified example of embodiment 1. The position of the second external terminal 5b may be a position 180 degrees opposite to the first external terminal 5a as in the example of Fig. 2, or may be a position shifted by 90 degrees from the first external terminal 5a as in the example of Fig. 3. The first external terminal 5a and the second external terminal 5b may be configured so that the positional relationship between the aluminum electrolytic capacitor 3 and the power semiconductor element 1 can be changed by remounting the printed circuit board 4.

[0023] FIG. 4 is a diagram illustrating a second modification of the first embodiment. In the example of FIG. 4, the first external terminal 5a is configured to be connectable to a first power semiconductor element 1a. The second external terminal 5b is configured to be connectable to a second power semiconductor element 1b of a different type from the first power semiconductor element 1a. In this example, a common printed circuit board 4 can be used for multiple types of power semiconductor elements 1 having different input terminal positions or sizes. This allows one printed circuit board 4 to be used for multiple types of power semiconductor elements 1, thereby extending the life of the printed circuit board 4 and reducing the number of types of printed circuit boards 4.

[0024] The power conversion device may include an insulating member that covers one of the first external terminal 5a and the second external terminal 5b that is not connected to the power semiconductor element 1. By preventing exposure of unused external terminals 5 among the multiple external terminals on the printed circuit board 4, it is possible to obtain effects such as countermeasures against electric shock and deterioration.

[0025] Next, a description will be given of a specific example of a method for estimating and notifying the life of the aluminum electrolytic capacitor 3. The remaining life Z of an aluminum electrolytic capacitor can be expressed by the following equations (1) and (2).

[0026] Z=1-(ha / La+hb / Lb+hc / Lc+...) (1) Lx=L0*2^{(T0-Tx) / 10} (x=a,b,c...) (2)

[0027] In equations (1) and (2), Z=1 means that the remaining life is 100% of the total life, and Z=0 means that the remaining life is zero. L0 is the specified endurance time of the aluminum electrolytic capacitor 3. T0 is the upper category temperature limit of the aluminum electrolytic capacitor. L0 and T0 are values ​​determined by the specifications of the aluminum electrolytic capacitor 3. Tx is the ambient temperature of the aluminum electrolytic capacitor 3 during actual use. hx is the usage time at ambient temperature Tx. Lx is the life time of the aluminum electrolytic capacitor at ambient temperature Tx.

[0028] The power conversion device of this embodiment is equipped with a temperature measurement unit 6 to estimate the ambient temperature Tx of the aluminum electrolytic capacitor 3. The temperature measurement unit 6 estimates the ambient temperature Tx of the aluminum electrolytic capacitor 3 from the observed value Ts of a temperature sensor such as a thermistor. The relationship between the observed value Ts of the temperature sensor and the ambient temperature Tx of the aluminum electrolytic capacitor 3 is determined in advance by experiment or the like. The ambient temperature Tx of the aluminum electrolytic capacitor 3 is determined in advance as a function using the observed value Ts of the temperature sensor as a variable, for example, as shown in the following equation (3).

[0029] Tx=f(Ts) (3)

[0030] In addition, when determining the ambient temperature Tx of the aluminum electrolytic capacitor 3, the value of the current flowing through the electric motor 10 may also be used as a parameter in addition to the value Ts observed by the temperature sensor. In this case, the value observed by the current sensor that observes the value of the current flowing through the electric motor 10 is also used to calculate the estimated value of the ambient temperature Tx of the aluminum electrolytic capacitor 3.

[0031] FIG. 5 is a diagram showing an example of observation by a temperature sensor in the first embodiment. The observation value Ts of the temperature sensor changes as the electric motor 10 operates and the air temperature changes. The ambient temperature Tx of the aluminum electrolytic capacitor 3 when the temperature sensor outputs observation values ​​Ts in the order Tsa, Tsb, and Tsc from a state in which the remaining life Z=1 is calculated using equation (3). The ambient temperatures Tx of the aluminum electrolytic capacitor 3 at the time when each observation value Ts is output are Ta, Tb, and Tc, respectively. The time resolution of the output by the temperature sensor is also Δt. In this case, ha, hb, and hc in equation (1) each become Δt, and the remaining life Z can be calculated using the following equation (4).

[0032] Z=1-(Δt / La+Δt / Lb+Δt / Lc) (4)

[0033] By continuing the calculation using Equation 4, it is possible to calculate the remaining life Z of the aluminum electrolytic capacitor 3 at each point in time. Note that the accuracy of the calculation of the remaining life Z increases if Δt is made smaller.

[0034] In the above example, a general simplified calculation formula was used as a method for calculating the lifespan of an aluminum electrolytic capacitor 3 mounted on a printed circuit board 4. If there is a calculation formula recommended by the manufacturer of the aluminum electrolytic capacitor 3, that calculation formula may be used.

[0035] We have explained how to calculate the remaining life Z for one aluminum electrolytic capacitor 3, but in reality, it is necessary to calculate the remaining life Z for each of the multiple aluminum electrolytic capacitors 3 being used. The relationship between the ambient temperature Tx of the aluminum electrolytic capacitor 3 and the temperature sensor observation value Ts, as shown in equation (3), varies depending on the relative positions of the aluminum electrolytic capacitor 3 and the power semiconductor element 1.

[0036] FIG. 6 is a diagram illustrating a method for calculating the remaining life Z of multiple aluminum electrolytic capacitors 3 in the first embodiment. For example, when six aluminum electrolytic capacitors 3 are used, as shown in FIG. 6, each aluminum electrolytic capacitor 3 is numbered 1 to 6 to identify the position of each aluminum electrolytic capacitor 3. The observed value Ts by the temperature sensor is input to the control unit 2, which then calculates the remaining life Z for each of the first to sixth aluminum electrolytic capacitors 3 using equations (1), (2), and (3). In the example of FIG. 6, the first aluminum electrolytic capacitor 3 or the second aluminum electrolytic capacitor 3 is located closer to the power semiconductor element 1, and therefore the remaining life Z decreases more quickly.

[0037] The notification by the notification unit 7 is performed using, for example, Z=0.5 in formula (1) as a threshold value. For example, when the remaining life of any one of the plurality of aluminum electrolytic capacitors 3 reaches Z=0.5 after starting use of the power conversion device, the first notification is performed.

[0038] After the first notification, the orientation of the printed circuit board 4 is changed, and information indicating that the position of each aluminum electrolytic capacitor 3 has been changed is input to the control unit 2. For example, the mounting orientation of the printed circuit board 4 may be defined by a number, such as "1" representing the initial orientation of the printed circuit board 4 and "2" representing the orientation rotated 180 degrees, and input to the control unit 2. In this way, it is preferable to set the relational expression (3) so that it automatically changes for each aluminum electrolytic capacitor 3 depending on the mounting orientation of the printed circuit board 4.

[0039] After changing the orientation of the printed circuit board 4, for example, when Z in equation (1) becomes 0, the second notification is executed. If the user finds that the remaining life of any of the aluminum electrolytic capacitors 3 is zero, he or she replaces the printed circuit board 4 with a new one.

[0040] In the above example, a notification is issued when the remaining life Z reaches a predetermined threshold value of 0.5 and zero. The timing of the notification is not limited to this and can be set arbitrarily. The criteria or thresholds that determine the timing of issuing a notification to prompt a change in the orientation of the printed circuit board 4 or a notification to prompt a replacement of the printed circuit board 4 can be set appropriately depending on the usage environment, etc. Furthermore, the orientation of the printed circuit board 4 may be changed multiple times.

[0041] Various aspects of the present disclosure are summarized below as appendices.

[0042] (Appendix 1) a power semiconductor element that converts input DC power into AC power and supplies the AC power to an electric motor; a control means for controlling a switching operation of the power semiconductor element; a plurality of aluminum electrolytic capacitors provided between positive and negative electrodes of the DC power; a printed circuit board on which the plurality of aluminum electrolytic capacitors are mounted; A power conversion device comprising: the control means estimates a remaining life of the aluminum electrolytic capacitor from an ambient temperature and a usage time of the aluminum electrolytic capacitor, and when the estimated remaining life reaches a reference value, causes a notification unit to issue a notification; the printed circuit board is provided with a first external terminal for connecting the power semiconductor element and a second external terminal different from the first external terminal; a power conversion device characterized in that the positional relationship between the plurality of aluminum electrolytic capacitors and the power semiconductor elements changes depending on whether the power semiconductor elements are connected to the first external terminals or the second external terminals. (Appendix 2) 2. The power conversion device according to claim 1, wherein the first external terminal is configured as a land that can be screwed to an input terminal of the power semiconductor element. (Appendix 3) The power conversion device according to claim 1 or 2, wherein the second external terminal is connectable to a power semiconductor element of a different type from the power semiconductor element. (Appendix 4) 4. The power conversion device according to claim 1, further comprising an insulating member covering one of the first external terminal and the second external terminal that is not connected to the power semiconductor element. [Explanation of symbols]

[0043] REFERENCE SIGNS LIST 1 power semiconductor element, 1a first power semiconductor element, 1b second power semiconductor element, 2 control unit, 3 aluminum electrolytic capacitor, 4 printed circuit board, 5 external terminal, 5a first external terminal, 5b second external terminal, 6 temperature measurement unit, 7 notification unit, 10 electric motor

Claims

1. a power semiconductor element that converts input DC power into AC power and supplies the AC power to an electric motor; a control means for controlling a switching operation of the power semiconductor element; a plurality of aluminum electrolytic capacitors provided between positive and negative electrodes of the DC power; a printed circuit board on which the plurality of aluminum electrolytic capacitors are mounted; A power conversion device comprising: the control means estimates a remaining life of the aluminum electrolytic capacitor from an ambient temperature and a usage time of the aluminum electrolytic capacitor, and when the estimated remaining life reaches a reference value, causes a notification unit to issue a notification; the printed circuit board is provided with a first external terminal for connecting the power semiconductor element and a second external terminal different from the first external terminal; a power conversion device characterized in that the positional relationship between the plurality of aluminum electrolytic capacitors and the power semiconductor elements changes between a state in which the power semiconductor elements are connected to the first external terminals and a state in which the power semiconductor elements are connected to the second external terminals.

2. The power conversion device according to claim 1 , wherein the first external terminal is configured as a land that can be screwed to an input terminal of the power semiconductor element.

3. 3. The power conversion device according to claim 1, wherein the second external terminal is connectable to a power semiconductor element of a type different from the power semiconductor element.

4. The power conversion device according to claim 1 or 2, further comprising an insulating member covering one of the first external terminal and the second external terminal that is not connected to the power semiconductor element.

Images