KR101327647B1 - Apparatus for diagnosing dc link capacitor of inverter - Google Patents

Abstract

Disclosed is a DC link capacitor diagnostic apparatus of an inverter. In the present invention, the DC power provided from the power supply to the motor is controlled to a certain size, when the voltage of the DC link reaches a predetermined voltage, to obtain the discharge time to reach the predetermined voltage, by using the DC link capacitor Diagnose the degree of degradation.

Description

Inverter DC Link Capacitor Diagnosis Device {APPARATUS FOR DIAGNOSING DC LINK CAPACITOR OF INVERTER}

The present invention relates to a diagnostic technique of an electrolytic capacitor, and more particularly, to an apparatus and method for diagnosing a DC link capacitor of an inverter.

In general, an inverter is connected to a three-phase AC commercial power source to smooth the AC power source to the DC power source, and generate the desired output by varying the frequency and voltage through PWM switching to supply the motor. Inverters are widely used in the industry because of their energy efficiency and ease of output control.

In the inverter, an electrolytic capacitor (hereinafter, referred to as a "DC link capacitor") that smoothes the DC power is installed to smooth the DC power to a certain level and accumulate or discharge electrical energy. Since the failure due to deterioration of the DC link capacitor is most frequent, it is very important to diagnose the failure by determining the degree of degradation of the DC link capacitor.

1 is a block diagram of a diagnostic apparatus for a conventional DC link capacitor.

In the apparatus for diagnosing the DC link capacitor 112 of the conventional inverter 110, a resistor 113 is connected in parallel with the DC link capacitor 112. In addition, a contactor 114 is connected in series with the resistor 113, and the contactor 114 is normally opened.

In addition, the voltage detector 116 is connected in parallel with the DC link capacitor 112, and the discharge detector 116, the deterioration determination circuit 118, and the interface 119 are connected to the voltage detector 116.

In the normal operation of the inverter 110, AC power is input using the breaker 100 connected to the rectifier 111, and AC power whose frequency is controlled from the inverter module 115 is output to the electric motor 120.

In this state, when the breaker 100 is opened and supply of power is stopped, the operation of the inverter module 115 is stopped, whereby the DC link capacitor 112 is in a state where charge is stored. At this time, when the contactor 114 is closed, the stored charge is discharged through the resistor 113.

When the capacitance of the capacitor 112 is C and the resistance value of the resistor 113 is R, the voltage between the anodes decreases according to the RC time constant by this discharge. This change in voltage is detected by the voltage detector 116 and transmitted to the discharge time measuring circuit 117. The discharge time measuring circuit 117 measures the discharge time from the change of the voltage and transmits the discharge time to the deterioration determination circuit 118.

The degradation determination circuit 118 compares the preset reference time with the discharge time, and outputs the degradation determination signal to the outside using the interface 119 when the discharge time is less than or equal to the reference time.

As described above, the conventional diagnostic apparatus measures the change in capacitance by measuring the discharge time by using the DC terminal voltage, thereby diagnosing the deterioration of the capacitor.

However, the above technique requires a component for diagnosing capacitor degradation only, such as the resistor 113 and the contactor 114, which is not required for normal operation of the inverter 110, and thus there is a problem in that additional cost is consumed. .

The technical problem of the present invention is to provide an apparatus and method for diagnosing a DC link capacitor of an inverter for diagnosing deterioration of a DC link capacitor of an inverter using an installed electric motor without requiring an additional circuit.

In order to solve the above technical problem, in an inverter including a DC link capacitor and an inverter unit, the apparatus of the present invention for diagnosing the DC link capacitor, the current detection unit for detecting a current supplied to the motor from the inverter unit; A power supply unit for supplying DC power; And controlling the DC power provided from the power supply unit to the electric motor to a predetermined size, and when the voltage of the DC link reaches a predetermined voltage, obtains a discharge time that reaches the predetermined voltage, and uses the same to determine the DC link capacitor. And a control unit for diagnosing the degree of deterioration.

In one embodiment of the present invention, the inverter unit is configured by connecting a plurality of switching elements and a plurality of diodes each connected in parallel to a three-phase full bridge, the control unit, by controlling the on and off of the plurality of switching elements It is preferable to control the DC power provided from the power supply unit to a predetermined size.

In one embodiment of the present invention, the inverter unit is configured by connecting the first to sixth switching elements and the first to sixth diodes in three-phase full bridges, respectively, connected in parallel, and the first to third switching elements. Form a path of the first phase current to the third phase current provided to the motor, it is preferable that the first switching element forms an upper leg, the second and the third switching element forms a lower leg.

In one embodiment of the present invention, the control unit, when the current supplied to the motor flows in the freewheeling mode, when the current supplied to the motor is reduced to a predetermined level or less than the command current, the predetermined first first It is preferable to control the third to third switching elements on.

In one embodiment of the present invention, the control unit, when the current supplied to the electric motor is increased by obtaining energy from the DC link capacitor, when the current supplied to the motor increases more than a predetermined level than the command current, It is preferable to control the first switching element to ON and to control the second and third switching element to OFF.

In one embodiment of the present invention, the control unit, when the current supplied to the electric motor is increased by obtaining energy from the DC link capacitor, when the current supplied to the motor increases more than a predetermined level than the command current, It is preferable to control the first switching element to off and to control the second and third switching elements to on.

In one embodiment of the present invention, it is preferable that the control unit controls the fourth to sixth switching elements to be off.

In one embodiment of the present invention, it is preferable that the controller estimates a change in capacitance of the DC link capacitor by a change in discharge time that reaches the predetermined voltage.

In one embodiment of the present invention, when the capacitance of the DC link capacitor is reduced to less than a predetermined ratio, it is preferable to diagnose the failure of the DC link capacitor.

In one embodiment of the present invention, it is preferable to further include a display unit for indicating that the DC link capacitor deteriorated by the diagnosis of the control unit.

In addition, in order to solve the above technical problem, in an inverter including a DC link capacitor and an inverter unit, the apparatus of the present invention for diagnosing the DC link capacitor, the current detection unit for detecting the current supplied to the motor from the inverter unit ; A power supply unit for supplying DC power; And controlling the DC power provided from the power supply unit to the electric motor to a predetermined size, and when a predetermined discharge time has elapsed, obtaining a voltage of the DC link at the discharge time, and deteriorating the DC link capacitor using the same. And a control unit for diagnosing the degree.

In one embodiment of the present invention, the control unit, it is preferable to estimate the change in the capacitance of the DC link capacitor by a change in the predetermined voltage in the discharge time.

In one embodiment of the present invention, when the capacitance of the DC link capacitor is reduced to less than a predetermined ratio, it is preferable to diagnose the failure of the DC link capacitor.

In one embodiment of the present invention, it is preferable to further include a display unit for indicating that the DC link capacitor deteriorated by the diagnosis of the control unit.

As described above, the present invention uses an electric motor that is already connected to discharge the DC link voltage, and thus has an effect of estimating the change rate of capacitance without requiring a separate discharge circuit.

In addition, the present invention can measure the change in capacitance more frequently than the conventional failure diagnosis, thereby improving the reliability and efficiency of the inverter, and prevents accidents such as component damage and fire caused by failure in advance. There is.

1 is a block diagram of a diagnostic apparatus for a conventional DC link capacitor.
2 is a diagram illustrating an embodiment of an inverter system to which the present invention is applied.
3A to 3D are exemplary views for explaining a state of an inverter under control of a controller of the diagnostic apparatus of the present invention.
4 is an exemplary view for explaining a switching waveform and a current state of a control unit according to the present invention.
FIG. 5 is an exemplary view illustrating a change in discharge time according to a voltage decrease for a DC link capacitor in a steady state and a DC link capacitor in a degraded state.
6 is a flowchart illustrating an example of a method for diagnosing a DC link capacitor according to the present invention.
7 is a detailed flowchart of an embodiment of S62 of FIG. 6.
FIG. 8 is an exemplary view illustrating a change in voltage decrease with discharge time for a DC link capacitor in a steady state and a DC link capacitor in a deteriorated state.
9 is a flowchart illustrating another embodiment for explaining a method of diagnosing a DC link capacitor according to the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Terms including ordinals such as first, second, etc. may be used to describe various elements, but the elements are not limited by such terms. These terms are used only to distinguish one component from another.

When a component is said to be 'connected' or 'connected' to another component, it may be directly connected to or connected to that other component, but other components may be present in between. It should be understood that. On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a component, or a combination thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating an embodiment of an inverter system to which the present invention is applied.

As shown in the figure, the inverter system to which the present invention is applied is composed of an AC power supply unit 1, an inverter 2, and an electric motor 3, and for diagnosing a DC link capacitor 22 of the inverter 2. The diagnostic device 4 of the present invention is connected. The power connection part 11 is arrange | positioned between the AC power supply part 1 and the inverter 2, and turns on / off the power supply to the inverter 2. As shown in FIG.

The diagnostic apparatus 4 of the present invention includes a switching mode power supply (SMPS 41), a control unit 42, a current measuring unit 43 and the display unit 44.

In addition, the inverter 2 includes a rectifier 21, a DC link capacitor 22, and an inverter 23.

First, the structure of the inverter 2 is demonstrated.

The rectifier 21 rectifies the input power which is three-phase alternating current input from the AC power supply 1. The DC link capacitor 22 smoothes the DC voltage rectified by the rectifier 21 and accumulates electrical energy. Although the DC link capacitor 22 is also referred to as a 'smooth electrolytic capacitor', the term 'DC link capacitor' will be used in the description of the present invention.

The inverter unit 23 is connected to the DC link capacitor 22 and supplies the smoothed DC voltage to the electric motor 3 through switching. That is, the inverter unit 23 connects six switching elements Q1 to Q6 and diodes D1 to D6 connected in parallel with each other in a three-phase full bridge, and is transferred from the DC link capacitor 22. The DC voltage to be converted is converted into three-phase alternating current and supplied to the electric motor 3. The switching elements Q1 to Q6 are, for example, insulated gate bipolar transistors (IGBTs), but are not limited thereto.

Hereinafter, the structure of the diagnostic apparatus 4 of this invention is demonstrated.

The SMPS 41 is connected to the rectifier 21 to supply a DC power supply for control.

The current detector 43 detects the magnitude of the load current supplied to the electric motor 3 and provides it to the controller 42.

The controller 42 controls the on / off of the six switching elements Q1 to Q6 of the inverter unit 23 to generate three-phase alternating current through a predetermined voltage and frequency. The control unit 42 is, for example, a microprocessor unit (MPU), but is not limited thereto.

Since the control unit 42 controls the switching of the inverter unit 23 to control the pulse width modulation (PWM) to drive the electric motor 3, it will be as well known in the art to which the present invention pertains, and thus a detailed description thereof will be omitted. Let's do it.

The operation of the diagnostic apparatus 4 of the present invention will be described below.

3A to 3D are exemplary views for explaining a state of an inverter under control of a controller of the diagnostic apparatus of the present invention. 3A to 3D show the state of the inverter 2, and the diagnostic apparatus 4 is not shown in FIGS. 3A to 3D.

As shown in FIG. 3A, when AC power is supplied from the AC power supply unit 1 and the power connection unit 11 is in contact (in FIG. 3A, a state in which the power connection unit 11 is in contact), the three-phase AC power supply is an inverter ( It is supplied to the rectifying part 21 of 2).

The AC power rectified by the rectifier 21 is smoothed by the DC link capacitor 22, converted into DC, and output.

The control unit 42 transmits a control signal to turn off the power connection unit 11 for diagnosis of the DC link capacitor 22, and then the control unit 42 provides a constant magnitude provided from the SMPS 41 to the electric motor 3. In order to provide a DC current of the above, Q1, Q2 and Q6 which are part of the switching elements Q1 to Q6 of the inverter section 23 are turned on / off. At this time, the remaining switching elements Q3, Q4 and Q5 are turned off. At this time, Q1, Q2 and Q6 are in charge of the path of the three-phase current provided to the motor 3, respectively, Q1 is a switching element of the upper leg, Q2 and Q6 are switching elements of the lower leg.

As shown in FIG. 3B, when Q1 is turned ON and Q2 and Q6 are turned OFF, current flows into a freewheeling mode through Q1, D3, and D5. . In this case, the current supplied to the electric motor 3 is gradually reduced by the resistance of the electric motor 3 and the power consumption of the SMPS 41.

4 is an exemplary view for explaining a switching waveform and a current state of a control unit according to the present invention.

When the control unit 42 turns on Q1 and turns off Q2 and Q6, the current Ias supplied to the electric motor 3 gradually decreases. When the current decreases and decreases below a predetermined level below the DC command current Idc, the control section 42 turns on Q2 and Q6 to be in a state as shown in FIG. 3C.

That is, as shown in FIG. 3C, the current supplied to the motor 3 flows from the terminal P through the motor 3 through the motor 3 to the terminal N through Q2 and Q6. At this time, the current is increased by obtaining energy from the DC link capacitor 22, and if the current is increased by a predetermined level or more, the control unit 42 turns off Q1 to be in a state as shown in FIG. 3D.

That is, as shown in FIG. 3D, when Q1 is turned off, current flows in a path through Q2, Q6, and D4, and becomes a freewheeling mode. In this case, too, the current is reduced by the resistance of the electric motor 3 and the power consumption of the SMPS 41. When the current decreases and decreases below a predetermined level from the current command, the control section 42 turns Q1 on again to form a current path as shown in Fig. 3C.

By repeating the switching pattern as described above, the DC current of a certain magnitude flows to the motor 3, it is possible to produce a constant power consumption. However, the above description of the control unit 42 applying the DC current having a predetermined size is exemplary, and is not limited thereto.

After the power connection part 11 of FIG. 2 is disconnected, when a DC current of a certain magnitude flows in the motor 3, power consumed by a resistance (not shown) of the motor 3 and power consumed by the SMPS 41 are shown. As a result, the DC link voltage decreases as shown in FIG. 4. This can be expressed as an equation related to energy. This will be described below.

The energy charged in the DC link capacitor 22 may be expressed as Equation 1 below.

In addition, the resistance of the electric motor 3 and the energy consumed by the SMPS 41 may be expressed by Equation 2 below.

Since the amount of change of energy charged in the DC link capacitor 22 is equal to the energy consumed for a predetermined time, the following Equation 3 can be derived by using Equations 1 and 2 above.

는 직류링크 커패시터(22)의 초기 커패시턴스,

은 측정시작전압,

은 직류링크의 전압이

일 때의 시간,

는 측정종료전압,

는 초기 커패시턴스에서 직류링크의 전압이

일때의 시간,

는 SMPS(41)에서 소모하는 전력,

은 전동기(3)의 저항(도시되지 않음)에서 소모하는 전력이다.

및

는 인버터(2)의 직류링크의 전압과 LV 트립(trip)이 발생하는 전압 사이에서 결정된다.here,

Is the initial capacitance of the DC link capacitor 22,

Is the measurement starting voltage,

Is the voltage of the DC link

Time when

Is the measurement end voltage,

Is the initial capacitance,

Time,

Power consumed by the SMPS 41,

Is the power consumed by the resistance (not shown) of the electric motor 3.

And

Is determined between the voltage of the DC link of the inverter 2 and the voltage at which the LV trip occurs.

When the DC link capacitor 22 deteriorates, the capacitance decreases and can be expressed by Equation 4 below.

는 열화된 후의 커패시턴스이고, 이때의 직류링크의 전압이

일 때의 시간을

로 나타내었다.here,

Is the capacitance after deterioration, and the voltage of the DC link

Time when

Respectively.

By dividing Equation 4 by Equation 3, a relational expression regarding capacitance and time can be obtained, which is shown in Equation 5 below.

는 정상적인 커패시터(22)에서의 방전시간이고,

는 열화된 커패시터(22)에서의 방전시간이다. here,

Is the discharge time in the normal capacitor 22,

Is the discharge time in the deteriorated capacitor 22.

The relationship of the above equation is shown in FIG. 5. FIG. 5 is an exemplary view illustrating a change in discharge time according to a voltage decrease for a DC link capacitor in a steady state and a DC link capacitor in a degraded state.

및

을 고정하고, 방전시간의 변화를 측정하여 직류링크 커패시터(22)의 커패시턴스의 변화를 추정할 수 있고, 이를 토대로 직류링크 커패시터(22)의 열화정도를 판단할 수 있다.That is, the controller 42 is the voltage of the DC link is required to measure

And

It is possible to estimate the change in capacitance of the DC link capacitor 22 by measuring the change in the discharge time, and to determine the degree of deterioration of the DC link capacitor 22 based on this.

Accordingly, the controller 42 estimates the ratio of the estimated DC link capacitor 22 to the initial value, and deteriorates the DC link capacitor 22 when the capacitance to the normal decreases to a predetermined ratio, for example, 85% or less. By determining, the failure of the DC link capacitor 22 is diagnosed.

When the control unit 42 diagnoses a failure of the DC link capacitor 22, the control unit 42 displays this on the display unit 44 to warn the user, thereby preventing accidents such as breakage of components and fire due to the failure of the DC link capacitor 22. To prevent it.

The following table shows an example of the result of the failure of the control section 42. The present invention is applied to an input power source of 220V and 380V and an inverter of various capacities, and the change rate is measured while changing capacitance.

7.5㎾-380V 22㎾-380V 7.5㎾-220V C _ini (㎌) 1500 4300 6000 t _{2 _ ini} (㎳) 0.105 0.188 0.216 C _old (㎌) 1000 500 3800 3300 5000 4000 C _old / C _ini (%) 66.7 33.3 88.4 76.7 83.3 66.7 t _{2 _ old} (㎳) 0.070 0.034 0.165 0.144 0.179 0.144 t _{2 _ old} / t _{2 _ ini} (%) 66.7 32.4 87.8 76.6 82.9 66.7

As described above, it can be seen that the rate of change of discharge time is closely related to the rate of change of capacitance at various power supply voltage levels and capacity bands. Therefore, the controller 42 of the present invention can reliably estimate the change in capacitance from the change in discharge time.

FIG. 6 is a flowchart illustrating a diagnosis method of a DC link capacitor according to the present invention, and illustrates a diagnosis method of the controller 42 of FIG. 2.

As shown in the figure, the control unit 42 of the present invention first transmits a control signal for turning off the power connection unit 11 connecting the AC power supply unit 1 and the inverter 2 to the power supply connection unit 11. (S61). As a result, the fault diagnosis of the present invention is started.

The control unit 42 controls the DC element of a predetermined magnitude to be applied to the electric motor 3 by turning on / off the switching element of the inverter unit 23 of the inverter 2 (S62), thereby reducing the voltage of the DC link. Observe.

7 is a detailed flowchart of an embodiment of S62 of FIG. 6.

As shown in the figure, the controller 42 of the present invention first turns off Q3, Q4 and Q5 of the switching elements of the inverter unit 23 in order to apply a DC current having a constant magnitude to the electric motor 3. In step S1, a control signal for controlling Q1 to be on and Q2 and Q6 to be off is transmitted to the inverter section 23 (S71). At this time, as shown in FIGS. 3B and 4, the current is in the freewheeling mode between the electric motor 3 and the inverter unit 23.

When the current supplied to the electric motor 3 decreases below the command current by a predetermined level or less (S72), the control unit 42 controls a control signal for controlling Q2 and Q6 to be turned on while Q1 is turned on. It transfers to the inverter part 23 (S73). At this time, as shown in Figure 3c and 4, the current flowing in the electric motor 3 is increased due to the energy of the DC link capacitor 22.

When the current supplied to the electric motor 3 increases above the command current by a predetermined level or more (S74), the control unit 42 controls a control signal for controlling Q1 to be off while Q2 and Q6 are on. It transmits to the inverter part 23 (S75).

In addition, when the current supplied to the electric motor 3 decreases below a predetermined level below the command current (S76), the control unit 42 controls Q1 to be turned on while the Q2 and Q6 are turned on. The signal is transmitted to the inverter unit 23 (S77). At this time, as shown in Figure 3c and 4, the current flowing in the electric motor 3 is increased due to the energy of the DC link capacitor 22.

In addition, when the current supplied to the electric motor 3 increases above the command current by a predetermined level or more (S78), the control unit 42 controls Q2 and Q6 to be turned off while Q1 is turned on. The signal is transmitted to the inverter unit 23 (S71), and the above process is repeated.

The current supplied to the electric motor 3 by the above S71 to S78 can be maintained at a constant size.

However, the method of controlling the control unit 42 of the present invention to apply a DC current having a constant magnitude to the electric motor 3 is not limited to the following description, and the DC current is uniformly applied by various other methods. You will be able to control it.

에 도달하는 경우에는(S63),

에 도달한 방전시간을 측정한다(S64).Then, in Figure 6, the DC link voltage is reduced to determine the predetermined termination voltage

If reaches (S63),

The discharge time reached to is measured (S64).

The controller 42 may then estimate the degree of deterioration of the capacitance relative to the normal with reference to Equation 5 (S65). If the estimated degree of degradation is less than or equal to a predetermined ratio (for example, 85%) (S66), the controller 42 diagnoses a failure of the DC link capacitor 22 (S67), and the corresponding DC link capacitor 22 ), The display unit 44 may be controlled to display that a failure has occurred (S68).

) 및 측정종료전압(

)을 고정하고 방전시간을 측정하였으나, 방전시간을 고정하고 측정시작전압(

) 및 측정종료전압(

)을 측정할 수도 있다.On the other hand, the control unit 42 of the present invention, in one embodiment described above, the measurement start voltage (

) And end voltage

) And the discharge time was measured, but the discharge time was fixed and the measurement start voltage (

) And end voltage

) Can also be measured.

FIG. 8 is an exemplary view illustrating a change in voltage decrease with discharge time for a DC link capacitor in a steady state and a DC link capacitor in a deteriorated state.

및

와 커패시턴스와의 관계를 다음 수학식 6과 같이 나타낼 수 있다.Using Equations 3 and 4 described above,

And

The relationship between and capacitance can be expressed as Equation 6 below.

는

과

를 고정하였을 때의 초기의 정상상태 커패시터(22)에서 감소된 전압의 레벨이고,

는 열화상태 커패시터(22)에서 감소된 전압의 레벨이다. 이와 같이, 방전시간을 고정하고, 전압의 변화를 측정하는 경우에도, 커패시턴스의 변화를 측정할 수 있다.
here,

The

and

Is the level of the reduced voltage at the initial steady state capacitor 22 when

Is the level of the reduced voltage at the deteriorated capacitor 22. In this way, even when the discharge time is fixed and the change in voltage is measured, the change in capacitance can be measured.

9 is a flowchart illustrating another embodiment for explaining a method of diagnosing a DC link capacitor according to the present invention.

As shown in the figure, in the diagnostic method of the present invention, the control unit 42, first, the control signal for turning off the power connection unit 11 connecting the AC power source unit 1 and the inverter 2, the power connection unit ( 11) (S91). As a result, the fault diagnosis of the present invention is started.

The control unit 42 controls the switching element of the inverter unit 23 of the inverter 2 to be turned on and off so that a DC current of a predetermined magnitude is applied to the motor 3 (S92), and whether a predetermined discharge time has elapsed. Observe. The detailed description of the above S92 will be the same as described with reference to FIG. 7, and thus description thereof will be omitted.

)을 측정한다(S94).After that, when the predetermined discharge time has elapsed (S93), the measurement end voltage at the discharge time (

) Is measured (S94).

The controller 42 may estimate the degree of deterioration of the capacitance relative to the normal with reference to Equation 6 (S95). If the estimated degree of degradation is less than or equal to a predetermined ratio (for example, 85%) (S96), the control unit 42 diagnoses a failure of the DC link capacitor 22 (S97), and the corresponding DC link capacitor 22 ), The display unit 44 may be controlled to display that a failure has occurred (S98).

Since the fault diagnosis of the present invention uses an electric motor already connected to discharge the DC link voltage, the change rate of capacitance can be estimated without requiring a separate discharge circuit.

Therefore, the present invention can be directly applied to commercially available inverters, and since there is no need to change hardware, there is an advantage that it can be applied as an upgrade form of software to already sold inverters.

In addition, since the change in capacitance can be measured more frequently than the conventional failure diagnosis, the reliability and efficiency of the inverter can be improved, and accidents such as component damage and fire caused by failure can be prevented in advance.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. Accordingly, the true scope of the present invention should be determined by the following claims.

1: AC power supply unit 11: power connection unit
2: inverter 21: rectifier
22: DC link capacitor 23: inverter section
3: electric motor 4: diagnostic device
41: SMPS 42: control unit
43: current measuring unit 44: display unit

Claims (14)

In the inverter comprising a DC link capacitor, a plurality of switching elements and a plurality of diodes connected in parallel to each other configured in a three-phase full bridge method, the device for diagnosing the DC link capacitor,
A current detector for detecting a current supplied to the motor from the inverter unit;
A power supply unit for supplying DC power; And
By controlling the on / off of the plurality of switching elements to control the DC power provided from the power supply unit to the electric motor to a predetermined size, when the voltage of the DC link reaches a predetermined voltage, the discharge time that reaches the predetermined voltage Obtaining, and using this to the diagnostic device comprising a control unit for diagnosing the degree of degradation of the DC link capacitor.
delete The switching device of claim 1, wherein the inverter unit is configured by connecting first to sixth switching elements and first to sixth diodes connected in parallel with each other in a three-phase full bridge, and the first to third switching elements are configured as described above. And a path of a first phase current to a third phase current provided to the motor, wherein the first switching element forms an upper leg, and the second and third switching elements form a lower leg.
The said control part of Claim 3 WHEREIN: When the electric current supplied to the said electric motor flows in a freewheeling mode, when the electric current supplied to the said electric motor falls below a predetermined level below a command current, predetermined said 1st thru | or 1st 3 Diagnosis device that controls the switching element on.
The method of claim 3, wherein the controller is configured to obtain the energy from the DC link capacitor, and when the current supplied to the motor increases, when the current supplied to the motor increases by a predetermined level or more than the command current, 1. A diagnostic apparatus for controlling the switching element on and controlling the second and third switching elements off.
The method of claim 3, wherein the controller is configured to obtain the energy from the DC link capacitor, and when the current supplied to the motor increases, when the current supplied to the motor increases by a predetermined level or more than the command current, And (1) controlling the switching element to be off and controlling the second and third switching elements to on.
The diagnostic apparatus according to any one of claims 3 to 6, wherein the controller controls the fourth to sixth switching elements to be off.
The diagnostic apparatus according to claim 1, wherein the control unit estimates a change in capacitance of the DC link capacitor by a change in discharge time that reaches the predetermined voltage.
The diagnostic apparatus of claim 8, wherein the control unit diagnoses a failure of the DC link capacitor when the capacitance of the DC link capacitor decreases below a predetermined ratio.
The method of claim 1,
And a display configured to display that the DC link capacitor has been degraded by the diagnosis of the controller.
In the inverter comprising a DC link capacitor and the inverter unit, In the device for diagnosing the DC link capacitor,
A current detector for detecting a current supplied to the motor from the inverter unit;
A power supply unit for supplying DC power; And
The DC power supplied from the power supply unit to the motor is controlled to a predetermined size, and when a predetermined discharge time has elapsed, the voltage of the DC link at the discharge time is obtained, and the degree of deterioration of the DC link capacitor is obtained using the same. Diagnostic device comprising a control unit for diagnosing the.
The diagnostic apparatus according to claim 11, wherein the control unit estimates a change in capacitance of the DC link capacitor by a change in a predetermined voltage in the discharge time.
The diagnostic apparatus of claim 12, wherein the control unit diagnoses a failure of the DC link capacitor when the capacitance of the DC link capacitor decreases below a predetermined ratio.
12. The method of claim 11,
And a display configured to display that the DC link capacitor has been degraded by the diagnosis of the controller.

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