Inverter device

Abstract

This invention provides an inverter device that, in a superimposed control method for suppressing inrush current flowing to the main transformer by superimposedly applying voltages from an external power source when the main power supply is turned on, can suppress inrush current from various external power sources. The inverter device generates a predetermined three-phase variable frequency voltage from a three-phase AC power source and includes: a main transformer that applies a first voltage from an external three-phase AC power source to the three-phase primary winding on the primary side and obtains a predetermined voltage from the three-phase secondary winding on the secondary side; and an inverter body comprising multiple inverter units connected to the three-phase secondary winding of the main transformer. The main transformer has a third three-phase winding on the primary side such that when the first voltage is applied to the three-phase primary winding, a second voltage lower than the first voltage is superimposedly applied to the primary side. The main transformer has connection terminals at both ends of each phase winding of the third three-phase winding.

Description

Technical Field

[0001] This invention relates to inverter devices for obtaining high voltage output, and more particularly to multi-inverter devices that can obtain high voltage output by using multiple inverter units. Background Technology

[0002] The need to save energy by changing the speed of AC motors is becoming increasingly widespread, primarily in industrial equipment. In particular, low-power, low-voltage AC motors are being combined with general-purpose inverters for energy-efficient operation. On the other hand, high-power, high-voltage AC motors are also being adapted for energy-efficient operation through speed changes, leading to the practical application of high-voltage inverters.

[0003] As background technology for inverter devices that output such high voltages, there is Patent Document 1. Patent Document 1 discloses an inverter device that generates a predetermined variable frequency voltage from an AC power source, comprising: a plurality of inverter units having smoothing capacitors; and a main transformer disposed on the input side of the inverter device, wherein a third winding is disposed on the AC power source side which is part of the main transformer, and the AC power is applied to the smoothing capacitors of the plurality of inverter units via the third winding for initial charging.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2002-345258 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] Patent Document 1 discloses an external initial charging method for initial charging the smoothing capacitor in an inverter unit using a power source other than the main power supply, as a technique for initial charging the smoothing capacitor at low cost and with good power efficiency.

[0009] On the other hand, an inverter device that generates a specified variable frequency voltage from an AC power source has multiple inverter units and a main transformer disposed on the input side of the inverter device. A third winding is disposed on the AC power source side in such a way as part of the main transformer. As a technique to suppress inrush current flowing to the main transformer, it is known that when the main power supply to the primary winding of the main transformer is turned on, a voltage from an external power source is superimposed and applied to the third winding as superposition control.

[0010] Therefore, by using other power sources that are used for external initial charging as external power sources for superposition control, it is possible to suppress inrush current without adding any components.

[0011] However, the suppression effect of inrush current based on superposition control depends on the phase difference between the external power supply and the main power supply. When the phase difference is large, there is a problem that the inrush current cannot be sufficiently suppressed. In particular, since the inverter manufacturer is outside the control of the external power supply of the user using the inverter, the wiring method of the transformer that generates the external power supply may not be the same as the wiring method of the main transformer of the inverter. Depending on the combination of the wiring methods of various transformers, there is a possibility that the phase difference will become larger and the inrush current cannot be suppressed.

[0012] Therefore, the present invention was made in view of the above-mentioned technical problems, and its object is to provide an inverter device that, in a superimposed control method of suppressing inrush current flowing to the main transformer by superimposedly applying voltage from an external power source when the main power is turned on, can suppress inrush current for various external power sources.

[0013] Technical solutions for solving technical problems

[0014] As an example, the present invention is an inverter device that generates a predetermined three-phase variable frequency voltage from a three-phase AC power supply. It includes: a main transformer that applies a first voltage from an external three-phase AC power supply to a three-phase primary winding on the primary side and obtains a predetermined voltage from a three-phase secondary winding on the secondary side; and an inverter body comprising multiple inverter units connected to the three-phase secondary winding of the main transformer. The main transformer has a third three-phase winding on the primary side such that when the first voltage is applied to the three-phase primary winding, a second voltage lower than the first voltage is superimposed and applied to the primary side. The main transformer has connection terminals at both ends of each phase winding of the third three-phase winding.

[0015] The effects of the invention

[0016] According to the present invention, an inverter device can be provided that, in a superimposed control method for suppressing inrush current flowing to the main transformer by superimposedly applying voltage from an external power source when the main power supply is turned on, can suppress inrush current for various external power sources. Attached Figure Description

[0017] Figure 1 This is a structural diagram of the inverter device in the embodiment.

[0018] Figure 2 This is a structural diagram of the inverter unit in the embodiment.

[0019] Figure 3 This is a diagram illustrating the timing of the applied voltage to the main transformer in the embodiment.

[0020] Figure 4 This is a diagram illustrating the phase of the applied voltage to the main transformer in the embodiment.

[0021] Figure 5 This is an explanatory diagram showing the connection method of the three-phase primary winding and the third three-phase winding of the main transformer in the embodiment, which is Y△1.

[0022] Figure 6 This is an explanatory diagram showing the connection method of the three-phase primary winding and the third three-phase winding of the main transformer in the embodiment, which is Y△11.

[0023] Figure 7 This is a diagram illustrating the connection terminals of the three-phase primary winding and the third three-phase winding of the main transformer in the embodiment.

[0024] Figure 8 This is a diagram illustrating other examples of the connection terminals of the three-phase primary winding and the third three-phase winding of the main transformer in the embodiment. Detailed Implementation

[0025] Hereinafter, embodiments of the present invention will be described using the accompanying drawings.

[0026] [Example]

[0027] Figure 1 This is a structural diagram of the inverter device in this embodiment. The inverter device in this embodiment generates a specified three-phase variable frequency voltage from a three-phase AC power supply. Figure 1 As shown, the inverter device 5 mainly includes: a main transformer 3 that applies the first voltage from the external three-phase AC power supply 1 to the three-phase primary winding 31 on the primary side and obtains a specified voltage from the three-phase secondary winding 32 on the secondary side; and an inverter body 4 that is connected to the three-phase secondary winding 32 of the main transformer 3 and includes multiple inverter units 41-49.

[0028] exist Figure 1 In this inverter, the three-phase AC power supply 1 is a power frequency AC power supply, which supplies its power to the three-phase primary winding 31 of the main transformer 3 via the main switch 11. The three-phase secondary winding 32 of the main transformer 3 consists of multiple three-phase windings, and each three-phase secondary winding 32 is connected to the AC input terminals of multiple inverter units 41-49 of the inverter body 4. In the inverter body 4, the AC power supplied by the three-phase AC power supply 1 is converted into variable frequency three-phase AC power to power the AC motor 9, which serves as the load. Figure 1 This indicates a triple-stage inverter, but this embodiment is not limited to triple-stage; it can be any n stages.

[0029] Figure 2 This is a structural diagram of inverter units 41-49 in this embodiment. Figure 2In this configuration, inverter units 41-49 are each configured such that their three-phase secondary windings 32 are connected to AC input terminals u, v, and w. The three-phase AC power supply 103 from the three-phase secondary windings 32 is converted into a DC voltage Vdc 105 by a three-phase full-wave diode rectifier 61 within each inverter unit. This DC voltage Vdc 105 is then smoothed using a smoothing capacitor 62. The smoothed DC voltage Vdc 105 is further converted into a single-phase variable frequency voltage 106 by each transistor inverter 63. Terminals a and b are the terminals connected to each inverter unit.

[0030] exist Figure 1 In the inverter units 41-43, each is connected to terminals a and b, and the single-phase variable frequency voltages 106 are connected in series and added together to generate a u-phase variable AC voltage; inverter units 44-46, each is connected to terminals a and b, and the single-phase variable frequency voltages 106 are connected in series and added together to generate a v-phase variable AC voltage; inverter units 47-49, each is connected to terminals a and b, and the single-phase variable frequency voltages 106 are connected in series and added together to generate a w-phase variable AC voltage, which is output as a three-phase variable AC voltage 104, for example, to drive an AC motor 9.

[0031] exist Figure 1 In this circuit, converter current transformers (CTs) and instrument transformers (PTs) installed on each layer detect the layer current and inter-layer voltage of each layer. Based on the detected layer current and inter-layer voltage, control circuit 52 generates gate pulses 53 for driving the transistor inverters 63 of inverter units 41-49. Here, 51 represents a grounding detection circuit (short circuit to ground detection circuit).

[0032] Furthermore, the main transformer 3 has a third three-phase winding 33 on its primary side. As a technique to suppress inrush current flowing to the main transformer 3, when the first voltage is applied to the three-phase primary winding 31, a second voltage, which is lower than the first voltage, is superimposed on the third three-phase winding 33. Here, the second voltage, as an external power source, is generated from the three-phase AC power supply 1 by the low-voltage transformer 2 and supplied to the third three-phase winding 33 via the auxiliary switch 21. For example, the three-phase AC power supply 1, which is the first voltage, is three-phase AC 6600V, and the second voltage, which is lower than it, is three-phase AC 200V to 440V.

[0033] Figure 3 This is a diagram illustrating the timing of the applied voltage to the main transformer 3 in this embodiment. Figure 3When the inverter device's operation command becomes ON, the auxiliary switch 21 closes and becomes ON, and a second voltage, generated by the low-voltage transformer 2 and lower than the first voltage, is applied to the third three-phase winding 33. Moreover, overlapping with the period when the auxiliary switch 21 closes and becomes ON, the main switch 11 closes and becomes ON, and a first voltage from the three-phase AC power supply 1 is applied to the three-phase primary winding 31.

[0034] Specifically, by applying the second voltage through the third winding to the smoothing capacitors of each of the plurality of inverter units, the initial charging of the smoothing capacitors can also be used as an external initial charging method that can be performed at low cost and with good power efficiency. Figure 3 During the period when the auxiliary switch 21 is closed and becomes ON, it becomes the initial charging time of the smoothing capacitor, for example, about 5 seconds.

[0035] Here, as a technique to suppress inrush current flowing to the main transformer 3, a superimposed control is applied by superimposing the voltage from the low-voltage power supply when the high-voltage power supply, which is the main power supply to the main transformer 3, is turned on. Regarding the characteristics, the effect varies due to the phase difference between the low-voltage power supply and the high-voltage power supply. For example, if the phase difference is 0, the inrush current is about 1 times the rated current; if the phase difference is ±30°, the inrush current is about 2 times the rated current; and if the phase difference is ±60°, the inrush current is about 5 times the rated current.

[0036] Figure 4 This is a diagram illustrating the phase of the applied voltage to the main transformer in this embodiment. Figure 4 China for and Figure 1 The same structure is assigned the same reference numerals, and their descriptions are omitted. Figure 4 In the middle section, the phase of the low-voltage power supply, i.e., phase A, is the phase from the first to the second winding of the low-voltage transformer 2. For example, if the connection method is delta-delta (hereinafter referred to as △△), the phase deviation is 0°; if it is star-delta (hereinafter referred to as Y△), the phase deviation is 30°. On the other hand, the phase of the high-voltage power supply, i.e., phase B, is the phase from the first three-phase winding 31 to the third three-phase winding 33 of the main transformer 3.

[0037] Figure 5 , Figure 6 This diagram illustrates the wiring configuration of the three-phase primary winding 31 and the third three-phase winding 33 of the main transformer 3. Figure 5 , Figure 6 In the diagram, the left image represents a vector diagram, and the right image represents a wiring diagram. Thick lines represent windings, and various wiring methods are used by different wiring at both ends of each winding. Figure 5 This indicates the case where the wiring method is Y△1. Figure 6This indicates the case where the wiring method is Y△11. For example... Figure 5 As shown, if the wiring method is Y△1, then the phase B is 30°, as... Figure 6 As shown, if the wiring method is Y△11, then the phase B is -30°. Furthermore, if the wiring method is star-to-star (hereinafter referred to as YY), then the phase B is 0, but this is not illustrated here.

[0038] Therefore, the phase difference between the low-voltage power supply and the high-voltage power supply is phase A - phase B. Wherein... Figure 4 In this context, R22 is a current-limiting resistor used when applying an external initial charging method.

[0039] Here, the wiring configuration of the low-voltage transformer 2 that generates the low-voltage power supply is not limited to the same configuration as that of the three-phase primary winding 31 and the third three-phase winding 33 of the main transformer of the inverter unit. In particular, since the manufacturer of the inverter unit 5 is outside the jurisdiction of the low-voltage transformer 2 on the user side of the inverter unit 5, depending on the combination of the wiring configurations of each transformer, there is a possibility that the phase difference will increase and the inrush current cannot be limited.

[0040] Therefore, in this embodiment, the main transformer on the inverter side has connection terminals at both ends of each of the three phase windings, enabling multiple wiring methods. Details of this embodiment will be described below.

[0041] Figure 7 This is a diagram illustrating the connection terminals of the three-phase primary winding 31 and the third three-phase winding 33 of the main transformer in this embodiment.

[0042] exist Figure 7 In the diagram, the connection terminals of the main transformer are indicated by white circles. For example, the connection terminals for the three-phase primary winding 31 include 1U, 1V, and 1W with Y-connection. The connection terminals for the third three-phase winding 33 include 3U1, 3V1, 3W1, and 3U2, 3V2, and 3W2. The connection terminals for the three-phase secondary winding 32 are omitted. That is, three terminals are provided for the three-phase primary winding 31 after connecting the three-phase windings, and six terminals are provided for the third three-phase winding 33 after the three-phase windings are not connected.

[0043] Therefore, when a user of inverter device 5 installs inverter device 5, they can connect the connection terminals of the third three-phase winding 33 of the main transformer using external connection wires, corresponding to the wiring method of the low-voltage transformer 2, thereby enabling a specified wiring configuration. For example, in Figure 7In this configuration, by connecting the wires as dashed lines (dotted lines), the three-phase primary winding 31 and the third three-phase winding 33 can be connected in a Y△1 configuration. Furthermore, by connecting the wires as discontinuous dashed lines, the three-phase primary winding 31 and the third three-phase winding 33 can be connected in a Y△11 configuration. Additionally, by connecting the wires as dashed-dot lines, the three-phase primary winding 31 and the third three-phase winding 33 can be connected in a YY configuration. Among these, in... Figure 7 In this circuit, a Y-connection is used for the three-phase primary winding 31, but a Δ connection can also be used.

[0044] Thus, because the connection method of the third three-phase winding 33 of the main transformer can be changed according to the connection method of the low-voltage transformer 2, the phase of the three-phase primary winding 31 and the third three-phase winding 33 can be arbitrarily adjusted, so that the phase difference between the low-voltage power supply and the high-voltage power supply is within 30°. As a result, the inrush current can be suppressed to within twice the rated current.

[0045] In addition, the manufacturer of inverter device 5 can also confirm the wiring method of the low-voltage transformer 2 of the user using inverter device 5, and connect the connection terminals of the third three-phase winding 33 of the main transformer with an external connection wire according to the wiring method.

[0046] Figure 8 This is a diagram illustrating another example of the connection terminals of the three-phase primary winding 31 and the third three-phase winding 33 of the main transformer in this embodiment. Figure 8 In China, for the sake of Figure 7 The same structures are assigned the same reference numerals, and their descriptions are omitted. Figure 8 In the middle, make Figure 7 The connection terminals 3W1 and 3W2 at both ends of one winding are configured in opposite directions.

[0047] exist Figure 8 In, with Figure 7 Compared to the previous method, when connecting the connection terminals of the third three-phase winding 33 using an external connection wire, the external connection wire can be shorter. Furthermore, by designing the configuration and shape of the connection terminals separately for the U, V, and W windings, a configuration that prevents incorrect wiring can be achieved.

[0048] As described above, according to this embodiment, an inverter device can be provided that, in a superimposed control method that suppresses inrush current flowing to the main transformer by superimposedly applying voltage from an external power source when the main power is turned on, can suppress inrush current for various external power sources.

[0049] The embodiments described above are not limited to the above embodiments and include various modifications. For example, in the above embodiments, it is described that the external power supply used for superposition control can also be used as another power supply for external initial charging, but this is not a limitation. Furthermore, in the above embodiments, the invention has been described in detail to facilitate understanding, but it is not limited to having all the structures described.

[0050] Explanation of reference numerals in the attached figures

[0051] 1: Three-phase AC power supply; 2: Low-voltage transformer; 3: Main transformer; 4: Inverter body; 5: Inverter unit; 9: AC motor; 11: Main switch; 21: Auxiliary switch; 22: Current limiting resistor; 31: Three-phase primary winding; 32: Three-phase secondary winding; 33: Third three-phase winding; 41-49: Inverter unit; 52: Control circuit; 53: Gate pulse; 61: Three-phase full-wave diode rectifier; 62: Smoothing capacitor; 63: Transistor inverter; 103: Three-phase AC power supply; 105: DC voltage Vdc; 106: Single-phase variable frequency voltage.

Claims

1. An inverter device for generating a specified three-phase variable frequency voltage from a three-phase AC power supply, characterized in that, include: The main transformer that applies the first voltage from the external three-phase AC power supply to the three-phase primary winding on the primary side and obtains the specified voltage from the three-phase secondary winding on the secondary side; and The inverter body, comprising multiple inverter units, is connected to the three-phase secondary winding of the main transformer. The main transformer has a third three-phase winding on the primary side, such that when the first voltage is applied to the three-phase primary winding, a second voltage, which is lower than the first voltage, is superimposed and applied to the primary side. The main transformer has connection terminals at both ends of each phase winding of the third three-phase winding. The three-phase primary winding is star-connected. By connecting the connection terminals, the three-phase primary winding and the third three-phase winding can be configured into a specified connection method among star-star connection, star-delta 1 connection, and star-delta 11 connection.

2. The inverter device as described in claim 1, characterized in that: The device includes a converter for detecting the layer current output from the plurality of inverter units and an instrument transformer for detecting the interlayer voltage, and generates gate pulses for driving the inverter units based on the detected layer current and the interlayer voltage.

3. The inverter device as described in claim 1, characterized in that: The second voltage is applied via the third three-phase winding to the smoothing capacitors of each of the plurality of inverter units for initial charging.

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