Fault diagnosis device for inverter initial charging circuit and method thereof

Abstract

The present invention relates to a fault sensing device for an initial charging circuit of an inverter and a method thereof. The initial charging circuit fault sensing device of the present invention uses a photo-coupler connected in parallel with an initial charging resistor of the initial charging circuit, and senses whether a relay of the initial charging circuit is malfunctioning or not using the situation that the photo-coupler is turned on if a current flows through the initial charging resistor in the on state of the relay, thereby having the effect of preventing a component from malfunctioning or burning due to a large current flowing through the initial charging resistor caused by a relay fault.

Description

TECHNICAL FIELD

[0001] The present invention relates to an inverter, and more particularly, to an initial charging circuit of an inverter. BACKGROUND

[0002] An inverter and a converter are one of representative power conversion devices. The inverter receives an alternating current power and converts it into a direct current, and then converts the direct current into an alternating current again in order to control a motor. The inverter is used in various forms in the entire industry using a motor such as a fan, a pump, an elevator, a transfer device, a production line, etc. The converter is a device that converts an alternating current or a direct current input power into a direct current, and its power conversion method is similar to that of the inverter, and like the inverter, it is used in various forms in the entire industry.

[0003] An initial charging circuit is essential in the inverter. The initial charging circuit prevents overcurrent caused by an inrush current from flowing in a direct current link capacitor of the inverter, and protects elements from high voltage generated by a parasitic inductance component of a rectifying portion and a direct current terminal and an inrush current.

[0004] Figure 1 A structure of a general inverter of the related art is shown.

[0005] The rectifying portion 10 converts a three-phase alternating current power into a direct current power and charges a direct current link capacitor 30, and the inverter portion 40 converts the direct current power stored in the direct current link capacitor 30 into an alternating current power again and delivers it to a motor.

[0006] In order to prevent overcurrent caused by an inrush current from flowing in the direct current link capacitor 30, an initial charging circuit 20 including an initial charging resistor and a relay is required to be equipped.

[0007] Figure 2 Flow of current at the time of initial charging and inverter operation is shown.

[0008] At the time of initial charging, the relay of the initial charging circuit 20 is in an off state, and thus, the output current of the rectifying portion 10 flows to the direct current link capacitor 30 via the initial charging resistor of the initial charging circuit 20. If the initial charging is completed, the relay will reach an on state, and the output current of the rectifying portion 10 will flow to the direct current link capacitor 30 and the inductor portion 40 via the relay of the initial charging circuit 20.

[0009] Figure 3 A voltage charged in the direct current link capacitor corresponding to time is shown.

[0010] If the DSP reset is cleared and the voltage of the DC link capacitor reaches above the low voltage clear (LVClear) level, the relay of the initial charging circuit turns on (Relay On), and after a ready time point, the voltage 32 that does not pass through the initial charging resistor of the initial charging circuit will be applied to the DC link capacitor as shown by the solid line. If the relay does not turn on and continues to pass through the initial charging resistor, the voltage 34 applied to the DC link capacitor will be as shown by the dotted line due to the voltage drop caused by the initial charging resistor.

[0011] However, even in the state where the relay is turned on, a voltage drop can occur when a light load is applied to the inverter, and thus it is not possible to distinguish the on / off of the relay only by the voltage drop. Therefore, there is a problem that it is not possible to determine whether or not the relay included in the initial charging circuit is malfunctioning by the voltage drop of the DC link capacitor.

[0012] The inventors of the present application have been studying the problem of the initial charging circuit malfunction detection method of the related art. In order to complete an apparatus and a method that can minimize the addition of components for detecting the malfunction of the initial charging circuit and can effectively detect the malfunction of the initial charging circuit, the present application has been completed after a great deal of effort. SUMMARY

[0013] PROBLEMS TO BE SOLVED BY THE INVENTION

[0014] The present application has been made in an effort to provide an apparatus and a method that can minimize the addition of components and can effectively detect the malfunction of a relay.

[0015] Another object of the present application is to detect the malfunction of a relay by adding a simple component, and to prevent power loss or malfunction burnout of components caused by an initial charging resistor, etc.

[0016] On the other hand, other objects of the present application that are not mentioned will be additionally considered within the range that can be easily inferred from the following detailed description and effects thereof.

[0017] TECHNICAL SOLUTION TO PROBLEM

[0018] The inverter initial charging circuit malfunction sensing apparatus of the present application includes:

[0019] a relay misoperation detection section including a photocoupler connected in parallel to an initial charging resistor of an inverter initial charging circuit, a voltage detection section including a first resistor connected in parallel to an output side of the photocoupler, and a control section that determines whether or not the relay misoperates by an output voltage output from the first resistor of the voltage detection section.

[0020] characterized in that the light coupler of the relay misoperation detection section is in an on state if current flows in the initial charging resistor.

[0021] Preferably, the voltage detection section further includes a second resistor, the first resistor and the second resistor being connected in series, the series-connected first and second resistors being connected in parallel with the DC link capacitor of the inverter.

[0022] If the output voltage of the first resistor is 0 after the initial charging of the inverter is completed and a run command is issued, the control section can determine that a failure has occurred in the initial charging circuit.

[0023] The failure sensing method of the initial charging circuit of the inverter according to another embodiment of the present application includes:

[0024] the step of turning on the relay after the initial charging of the inverter is completed; the step of starting the run of the inverter; the step of sensing the voltage drop of the DC link capacitor; the step of determining whether the light coupler connected in parallel with the initial charging resistor of the initial charging circuit of the inverter is on or off; and the step of determining that the relay of the initial charging circuit is misoperated if the light coupler is in an on state.

[0025] characterized in that whether the light coupler is on or off is determined by measuring the voltage of the resistor connected in parallel with the output side of the light coupler.

[0026] Effects of the Invention

[0027] According to the present application, there is an effect that the failure of the initial charging circuit can be effectively detected by adding the light coupler without using an additional power source or control section.

[0028] In addition, since a voltage detection method based on an existing OP AMP (OPerational AMPlifier) or the like is not used, there is an advantage that costs can be saved.

[0029] On the other hand, it is to be understood that even if the effects not explicitly mentioned herein are not explicitly mentioned herein, the effects described in the following description and potential effects expected by the technical features of the present application are all considered to be described in the specification of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a configuration diagram of a general inverter of the related art.

[0031] Figure 2 shows the flow of current corresponding to the on / off of the relay in the inverter of the related art.

[0032] Figure 3 The level at which the voltage is charged in the prior art DC link capacitor is shown.

[0033] Figure 4 A configuration diagram of the initial charging circuit fault sensing device of a preferred embodiment of the present application is shown.

[0034] Figure 5 A more detailed configuration diagram of the initial charging circuit fault sensing device of the present application is shown.

[0035] Figure 6 The voltage levels of the DC link capacitor according to different operations are shown.

[0036] Figure 7 An example of the signal detected according to the present application is shown.

[0037] Figure 8 A flowchart of the initial charging circuit fault sensing method of another preferred embodiment of the present application is shown.

[0038] * It is to be clearly understood that the attached drawings are included to serve as an aid in understanding the technical idea of the present application, and do not limit the scope of protection of the present application. DETAILED DESCRIPTION

[0039] Hereinafter, the configuration of the present application suggested by various embodiments of the present application and effects obtained from the configuration will be described with reference to the accompanying drawings. With respect to well-known functions related to the explanation of the present application, detailed description thereof will be omitted insofar as it is apparent to those skilled in the art and judged to make the gist of the present application unclear.

[0040] The terms "first", "second", and the like can be used to describe various structural elements, but the structural elements should not be limited to the above terms. The above terms can be used only to distinguish one structural element from another structural element. For example, "a first structural element" can be named "a second structural element" without departing from the scope of the present application, and similarly, "a second structural element" can also be named "a first structural element". In addition, unless the context clearly dictates otherwise, a singular expression includes a plural expression. Unless otherwise defined, the terms used in the embodiments of the present application can be interpreted as the meanings well known to those skilled in the art.

[0041] Hereinafter, the configuration of the present application suggested by various embodiments of the present application and effects obtained from the configuration will be described with reference to the accompanying drawings.

[0042] Figure 4 A configuration diagram of the initial charging circuit fault sensing device 100 of a preferred embodiment of the present application is shown.

[0043] The initial charging circuit failure sensing device 100 includes a relay misoperation detection section 110, a voltage detection section 120, and a control section 130.

[0044] The relay misoperation detection section 110 is connected in parallel to an initial charging resistor of the initial charging circuit, and detects misoperation of the relay.

[0045] The voltage detection section 120 is connected in parallel to the DC link capacitor, and detects a voltage of the DC link capacitor and a voltage for determining misoperation of the relay.

[0046] The control section 130 includes one or more processors, and determines misoperation of the relay from the voltage detected by the relay voltage detection section 120.

[0047] Figure 5 is a more detailed configuration diagram of the initial charging circuit failure sensing device 100 of the present application.

[0048] The relay misoperation detection section 110 includes an input resistor 112 and an optocoupler 114. The input resistor 112 is connected in series to an input side of the optocoupler 114.

[0049] The voltage detection section 120 includes a first resistor 124, a second resistor 122, and a voltage measurer 126. The first resistor 124 and the second resistor 122 are connected in series, and the series-connected first resistor 124 and second resistor 122 are connected in parallel to the DC link capacitor. The first resistor 124 is connected in parallel to an output of the optocoupler 114 of the relay misoperation detection section 110.

[0050] In the initial charging circuit, if the inverter is in a run state after the initial charging is completed, the relay is in an on state, and thus current does not flow to the initial charging resistor. Then, current does not flow in the optocoupler 114 of the relay misoperation detection section 110, and thus the optocoupler 114 is in an open state. If the optocoupler 114 is in the open state, the voltage measurer 126 measures a voltage applied to the first resistor 124, but, since the first resistor 124 and the second resistor 122 are connected in series, a voltage applied to the DC link capacitor is distributed according to the resistance ratio. For example, if the voltage applied to the DC link capacitor is 330 V, the first resistor 124 is 20 kΩ, and the second resistor 122 is 200 kΩ, the voltage applied to the first resistor 124 will be only 1 / 10 of the voltage applied to the second resistor 122, and thus the voltage distributed to the first resistor 124 is 30 V, and the voltage distributed to the second resistor 122 is 300 V. Thus, the voltage measured by the voltage measurer 126 will be 30 V.

[0051] On the other hand, if the inverter is in operation after the initial charging is completed, but the relay of the initial charging circuit is not in the on state, it can be judged that the relay is in the misoperation. If the relay is in the off state, the current flows in the initial charging resistor, not in the relay. If the current flows in the initial charging resistor, the current also flows in the photodiode 114 connected in parallel to the initial charging resistor, and the photodiode 114 is in the on state.

[0052] If the photodiode 114 is in the on state, the both ends of the photodiode 114 are in the short circuit state, and therefore, the both ends of the first resistor 124 of the voltage detection unit 120 are also short-circuited. Therefore, the voltage measurement device 126 measuring the voltage of the both ends of the first resistor 124 will detect the voltage of 0. At this time, the voltage is lowered by the initial charging resistor, and therefore, the voltage of the both ends of the DC link capacitor is lower than the normal case.

[0053] If the voltage of the both ends of the DC link capacitor is lower than the normal, and the voltage measured in the voltage measurement device 126 is lower than the reference value, the control unit 130 can judge that the relay of the initial charging circuit is in the failure. If the voltage of the both ends of the DC link capacitor is lower than the normal, but the value measured in the voltage measurement device 126 is higher than the reference value, it can be judged that it is the light load operation of the inverter, not the failure of the relay.

[0054] Figure 6 The reference voltage of the DC link capacitor for judging the failure of the initial charging circuit in the control unit as described above is shown.

[0055] The SMPS (Switching Mode Power Supply) for the operation of the entire inverter is always operated above the very small voltage 66.

[0056] The operation voltage of the inverter is maintained between the overvoltage level 61 and the low voltage level 65 at which the relay is turned on after the initial charging is completed. Preferably, the rated voltage should be maintained between the rated maximum voltage 62 and the rated minimum voltage 64. In the case where the relay is in the on state, the DC link capacitor is maintained at the predetermined charging voltage 63 without the voltage drop by the initial charging resistor, and in the case of the failure of the relay or the light load operation, etc., it is also lowered to below the charging voltage 63. At this time, using the relay misoperation detection unit 110 and the voltage detection unit 120, the control unit can judge whether it is the normal voltage drop or the voltage drop by the relay misoperation.

[0057] Figure 7 An example of the signal detected at the time of the relay misoperation is shown.

[0058] A change in the signal occurs at the time point 77 at which the relay misoperation starts.

[0059] The DC-link voltage shows the voltage 71 measured before the initial charging circuit and the voltage 72 measured in the DC-link capacitor. If the relay misoperates, the output current of the rectifying section will pass through the initial charging resistor, so the voltage measured before the initial charging circuit will have more riffle. In addition, the voltage 72 applied to the DC-link capacitor will drop due to the initial charging resistor.

[0060] The relay switches from the on state 73 to the off state 74 due to the misoperation.

[0061] If the optocoupler 114 is on when the relay misoperates, the voltage 76 detected by the voltage detecting section 120 will drop to 0.

[0062] Figure 8 A flowchart of the initial charging circuit failure sensing method according to another preferred embodiment of the present application.

[0063] If the power supply of the inverter is turned on (step S10), and the SMPS for controlling the entire inverter is operated (step S20), the initial charging is started.

[0064] If the voltage charged in the DC-link capacitor reaches the inverter low voltage clear (LV Clear) level (step S30), the initial charging is ended, and if the relay of the initial charging circuit switches to the on state (step S40), the inverter starts the formal operation (Run) (step S50).

[0065] The control section judges whether a voltage drop occurs in the DC-link capacitor (step S60), and judges whether the voltage drop is caused by the failure of the relay or by the normal low voltage operation.

[0066] To this end, the control section judges the state of the optocoupler connected in parallel with the initial charging resistor, and the state of the optocoupler is judged by the voltage applied to the resistor connected in parallel with the output side of the optocoupler. If the optocoupler is in the on state, it is short-circuited, so the voltage of the resistor connected in parallel therewith will be 0, and if the optocoupler is in the off state, it is open, so the voltage of the resistor connected in parallel therewith will not be 0.

[0067] Therefore, it is judged whether the voltage detected from the resistor connected in parallel with the optocoupler is below the reference voltage (step S70), and if it is below the reference voltage, it is judged that the relay misoperates (step S80), and a control such as displaying a warning message or stopping the operation of the inverter can be performed.

[0068] According to the present application as described above, the effect that whether the relay of the initial charging circuit is faulty or not can be effectively determined with the optical coupler which does not require an additional power source or a control section.

[0069] The scope of the present application is not limited to the recitation and description of the above-mentioned embodiments. Furthermore, it is reiterated that modifications or substitutions apparent to those skilled in the art cannot limit the scope of the present application.

Claims

1. An inverter initial charging circuit failure sensing device characterized by comprising: a relay misoperation detection section including an optocoupler whose input side is connected in parallel to an initial charging resistor of an inverter initial charging circuit; a voltage detection section including a first resistor connected in parallel to an output side of the optocoupler; and a control section that judges whether or not a relay misoperation by an output voltage from the first resistor of the voltage detection section, the voltage detection section further includes a second resistor, the first resistor and the second resistor are connected in series, the series-connected first resistor and second resistor are connected in parallel to a DC link capacitor of the inverter, if the output voltage of the first resistor is 0 after an operation command is issued after initial charging of the inverter is completed, the control section judges that the initial charging circuit has failed.

2. The inverter initial charging circuit failure sensing device according to claim 1, characterized in that if a current flows in the initial charging resistor, the optocoupler of the relay misoperation detection section is in an on state.

3. An inverter initial charging circuit failure sensing method executed by a control section including one or more processors, characterized by comprising: a step of turning on a relay after initial charging of an inverter is completed; a step of starting operation of the inverter; a step of sensing a voltage drop of a DC link capacitor; a step of judging whether or not an optocoupler connected with an input side in parallel to an initial charging resistor of an inverter initial charging circuit and with an output side in parallel to a first resistor is on or off; and a step of judging that a relay of the initial charging circuit misoperates if the optocoupler is in an on state; the step of judging whether or not the optocoupler connected with the input side in parallel to the initial charging resistor of the inverter initial charging circuit and with the output side in parallel to the first resistor is on or off includes a step of judging whether or not the optocoupler is on or off by measuring a voltage of the first resistor connected in parallel to the output side of the optocoupler; the first resistor and a second resistor are connected in series, and the series-connected first resistor and second resistor are connected in parallel to a DC link capacitor of the inverter; if the output voltage of the first resistor is 0 after an operation command is issued after initial charging of the inverter is completed, the control section judges that the optocoupler is in an on state, and thus judges that the initial charging circuit has failed. ​ ​

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