Control cabinet and refrigeration equipment

Abstract

The invention provides a control cabinet and refrigeration equipment, and belongs to the technical field of refrigeration. The control cabinet comprises a frequency converter, a drainage circuit and a grounding end, the voltage input end of the frequency converter is used for being connected with a live wire of an alternating current power supply, the voltage output end is used for being connected with the driving end of the motor, the first end of the drainage circuit is electrically connected with the grounding end of the control cabinet, and the second end of the drainage circuit is used for being connected with a neutral wire of the alternating current power supply. Ground leakage current generated based on induced electromotive force on the motor shell flows back to the neutral line of the alternating current power supply through the drainage circuit, the ground leakage current is effectively reduced, the requirement for the low allowable value of the ground leakage current can be met, the motor shell is connected to the ground protection line of the alternating current power supply through the ground end, the electric shock phenomenon caused by human body contact can be avoided, and the service life of the motor is prolonged. And the use safety of the motor is effectively improved.

Description

Technical Field

[0001] The present application relates to the field of refrigeration technology, and in particular to a control cabinet and refrigeration equipment. Background Art

[0002] With the continuous development of refrigeration equipment, the demand for its application in medical and supporting fields is also gradually increasing. Compared with traditional industrial equipment, electrical equipment in the medical industry has higher safety level requirements. For example, in the medical field, the allowable value of ground leakage current of refrigeration equipment or supporting electrical equipment is not more than 5mA.

[0003] In the process of implementing this application, the inventors found that there are at least the following technical problems in the prior art:

[0004] Refrigeration equipment usually uses a frequency converter to control the fan so that the fan is controlled and speed-regulated. When the three-phase winding of the fan passes current, a rotating magnetic field is generated, causing the fan housing to generate an induced electromotive force. The magnitude of this electromotive force depends on the switching frequency of the IGBT (Insulated-Gate Bipolar Transistor) in the frequency converter. In theory, the higher the switching frequency, the greater the induced electromotive force on the fan housing, and the ground leakage current will be generated based on the induced electromotive force. In order to reduce the ground leakage current of the refrigeration equipment, an existing practice is usually to set the fan housing to a floating state, thereby cutting off the path of the current formed by the induced electromotive force of the fan housing to the ground, thereby eliminating the ground leakage current generated by the induced electromotive force of the fan housing.

[0005] However, the induced electromotive force of the fan casing can generally be as high as several hundred volts. If the fan casing is in a floating state, a person may feel an electric shock after touching it, which will cause the refrigeration equipment to fail to meet the requirements of safety regulations. Summary of the invention

[0006] In order to effectively solve the technical problems existing in the prior art, the present application provides a control cabinet and refrigeration equipment with low ground leakage current and high safety performance.

[0007] According to a first aspect of an embodiment of the present application, there is provided a control cabinet, including a frequency converter, a current drainage circuit and a grounding terminal;

[0008] The voltage input terminal of the frequency converter is used to be connected to the live wire of the AC power supply, and the voltage output terminal of the frequency converter is used to be connected to the driving end of the motor;

[0009] The first end of the current drain circuit is electrically connected to the ground terminal, the second end of the current drain circuit is used to be connected to the neutral line of the AC power supply, and the current drain circuit is used to drain the ground leakage current to the neutral line, and the ground leakage current is generated based on the induced electromotive force on the housing of the motor;

[0010] The grounding terminal is used to be electrically connected to the protective grounding wire of the AC power supply and the housing of the motor respectively.

[0011] Optionally, the current diversion circuit includes a Y capacitor connected between the first end and the second end, and the ground leakage current flows to the neutral line through the Y capacitor.

[0012] Optionally, the Y capacitor includes a first Y capacitor and a second Y capacitor connected in series between the first end and the second end.

[0013] Optionally, the second end is used to be connected to a neutral line output end of a leakage protector so as to be connected to the neutral line via the leakage protector.

[0014] Optionally, the frequency converter includes a rectifier and filter circuit and a power conversion circuit;

[0015] The rectifier and filter circuit is used to rectify and filter the AC power output by the AC power supply, and provide DC power to the input end of the power conversion circuit via the DC bus. The power conversion circuit is used to convert the DC power into AC power with adjustable frequency to drive the motor to work;

[0016] A negative DC bus in the DC bus is electrically connected to the ground terminal.

[0017] Optionally, the control cabinet further includes a circuit breaker;

[0018] The circuit breaker is connected to the voltage input end of the frequency converter, and the voltage input end of the frequency converter is correspondingly connected to the live wire of the AC power source via the circuit breaker.

[0019] Optionally, the control cabinet further includes a three-phase filter circuit;

[0020] The three-phase filter circuit is connected to the voltage input end of the frequency converter, and the voltage input end of the frequency converter is correspondingly connected to the live wire of the AC power supply via the three-phase filter circuit;

[0021] The current drain circuit is connected to the neutral line via the three-phase filter circuit.

[0022] Optionally, the motor is an external fan in a refrigeration device.

[0023] According to a second aspect of the embodiments of the present application, a refrigeration device is provided, comprising a control cabinet and a fan according to any one of the aspects of the embodiments of the present application;

[0024] The grounding terminal of the control cabinet is electrically connected to the fan, and the voltage output terminal of the frequency converter in the control cabinet is connected to the driving terminal of the fan.

[0025] Optionally, there are multiple fans, and metal casings of the multiple fans are electrically connected to the grounding terminal of the control cabinet respectively.

[0026] The control cabinet and refrigeration equipment provided by this application have at least the following beneficial effects:

[0027] The control cabinet provided in the present application is provided with a drainage circuit between the ground terminal and the neutral line of the AC power supply, and the motor casing is electrically connected to the grounding protection line of the AC power supply via the ground terminal. The ground leakage current generated by the induced electromotive force on the motor casing can flow back to the neutral line via the drainage circuit, thereby effectively reducing the ground leakage current and meeting the low allowable value requirement for the ground leakage current. There is no electric shock when a human body touches the motor casing, thereby effectively improving the safety of the control cabinet. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are only used to illustrate the embodiments and are not to be considered as limiting the present invention. In addition, the same reference symbols are used to represent the same components throughout the accompanying drawings. In the accompanying drawings:

[0029] Figure 1 A schematic diagram of the structure of a control cabinet provided according to some embodiments of the present application;

[0030] Figure 2 A schematic diagram of the structure of a control cabinet provided according to other embodiments of the present application;

[0031] Figure 3 A schematic diagram of the structure of a control cabinet provided according to some other embodiments of the present application;

[0032] Figure 4 This is a schematic diagram of the structure of a three-phase filter circuit in a control cabinet provided according to some embodiments of the present application. DETAILED DESCRIPTION

[0033] The technical solution of the present application is further elaborated in detail below in conjunction with the accompanying drawings and specific embodiments of the specification.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit the implementation of this application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0035] In the description of this application, unless otherwise specified, "plurality" means two or more than two. In addition, in the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be internal communication between two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0036] See also Figure 1 As shown, it is a schematic diagram of the structure of the control cabinet 2 provided according to some embodiments of the present application. The control cabinet 2 provided in some embodiments of the present application can be used, but not limited to, to control the operation of the fan in the refrigeration equipment. In some embodiments, the control cabinet 2 includes a frequency converter 21, a current diversion circuit 22 and a ground terminal GND.

[0037] The voltage input terminal of the inverter 21 is used to connect to the live wire of the AC power supply, and the voltage output terminal of the inverter 21 is used to connect to the driving end of the motor 3. The first end P1 of the drainage circuit 22 is electrically connected to the ground terminal GND, and the second end P2 of the drainage circuit 22 is used to connect to the neutral line N of the AC power supply 1. The drainage circuit 22 is used to drain the ground leakage current to the neutral line N, and the ground leakage current is generated based on the induced electromotive force on the housing of the motor 3. The ground terminal GND is used to be electrically connected to the protective grounding wire PE of the AC power supply 1 and the housing of the motor 3 respectively.

[0038] The voltage input terminal of the frequency converter 21 includes a first phase voltage input terminal A, a second phase voltage input terminal B and a third phase voltage input terminal C, wherein the first phase voltage input terminal A is connected to the first phase live wire L1 of the AC power supply 1, the second phase voltage input terminal B is connected to the second phase live wire L2 of the AC power supply 1, and the third phase voltage input terminal C is connected to the third phase live wire L3 of the AC power supply 1. The voltage output terminal of the frequency converter 21 includes a first phase voltage output terminal U, a second phase voltage output terminal V and a third phase voltage output terminal W, and the first phase voltage output terminal U, the second phase voltage output terminal V and the third phase voltage output terminal W are electrically connected to the three windings of the motor respectively. The motor 3 can be, but is not limited to, a fan in a refrigeration device, and can be specifically an external fan.

[0039] The current diversion circuit 22 has the characteristics of passing high frequencies and blocking low frequencies, and is used to change the flow path of the ground leakage current generated by the induced electromotive force on the housing of the motor 3 from flowing to the earth to flowing to the neutral line N, thereby reducing the ground leakage current, which can meet the low allowable value requirement of the ground leakage current, thereby meeting the safety level index. In addition, the housing of the motor 3 is electrically connected to the ground terminal GND, and the ground terminal GND is connected to the protective ground wire PE of the AC power supply 1. When the human body touches the housing of the motor 3, there will be no electric shock, which effectively improves the safety performance of the motor.

[0040] In the control cabinet 2 provided in some embodiments of the present application, the drainage circuit 22 may be, but is not limited to, a capacitor circuit composed of capacitors, based on the high-frequency resistance and low-frequency characteristics of the capacitors, to drain the ground leakage current to the neutral line N. In some embodiments, the drainage circuit includes a Y capacitor connected between the first end P1 and the second end P2, and the ground leakage current flows to the neutral line through the Y capacitor. The Y capacitor may be a single capacitor, or may be composed of multiple Y capacitors connected in series and / or in parallel.

[0041] In some embodiments, considering the withstand voltage and life of the Y capacitor, there may be breakdown short circuit or open circuit in actual equipment operation, and two Y capacitors are connected in series between the first terminal P1 and the second terminal P2 to effectively improve the safety and reliability of the control cabinet. Figure 1 As shown, the Y capacitor connected in series between the first terminal P1 and the second terminal P2 includes a first Y capacitor Cy1 and a second Y capacitor Cy2.

[0042] See also Figure 2 As shown, it is a schematic diagram of the structure of the control cabinet 2 provided according to other embodiments of the present application. In other embodiments, the second end P2 of the diversion circuit 22 is used to connect to the neutral line output end of the leakage protector 4, so as to be connected to the neutral line N via the leakage protector 4. The motor 3 is a three-phase load. Due to the imbalance of the three-phase voltage or the imbalance of the three-phase load design, current will appear in the neutral line N. When the three-phase load is not provided with a terminal connected to the neutral line N, the leakage protector 4 (residual current protector) may be unable to detect the neutral line current caused by the imbalance of the three-phase load, and it is easy to malfunction, thereby causing the equipment to easily have leakage current, which is not conducive to the safe use of the equipment. In this embodiment, the second end P2 of the drainage circuit 22 is connected to the neutral line output end of the leakage protector 4, and connected to the neutral line N of the AC power supply 1 via the neutral line output end, which can not only reduce the leakage current to the ground, but also allow the neutral line current to flow back to the neutral point of the three-phase transformer in the AC power supply through the drainage circuit when there is a multi-phase unbalanced current caused by factors such as multi-phase load imbalance, so that the leakage protector 4 can detect the neutral line current, effectively reduce or avoid the false tripping of the leakage protector 4, reduce the leakage current of the entire load equipment, and improve the power safety of the equipment.

[0043] The AC power supply 1 can be a three-phase AC power supply, specifically a three-phase five-wire AC power supply. The three-phase five-wire AC power supply includes a three-phase five-wire AC transformer and a three-phase live wire, a neutral wire N and a ground protection wire PE derived from the three-phase five-wire AC transformer. The input end of the leakage protector 4 includes a multi-phase live wire input end and a neutral wire input end, and the output end of the leakage protector 4 includes a multi-phase live wire output end and a neutral wire output end. The multi-phase live wire input end of the leakage protector 4 is used to be connected to the multi-phase live wire of the AC power supply 1, and the neutral wire input end of the leakage protector 4 is connected to the neutral wire N of the AC power supply 1. The multi-phase live wire output end of the leakage protector 4 is connected to the multi-phase voltage input end of the frequency converter 21. A leakage protection switch and a current transformer are connected between the input and output ends of the leakage protector 4. The leakage protector 4 detects the current difference between the live wire and the neutral wire N connecting wire of each phase based on the current transformer. When the current difference exceeds a preset value, the leakage protection switch of the corresponding phase is disconnected to perform leakage protection.

[0044] Please continue reading Figure 2 As shown, in other embodiments, the frequency converter 21 includes a rectifier filter circuit 211 and a power conversion circuit 212. The rectifier filter circuit 211 is used to rectify and filter the AC power output by the AC power source 1, and provide DC power to the input end of the power conversion circuit 212 via the DC bus. The power conversion circuit 212 is used to convert the DC power into an AC power with adjustable frequency to drive the motor 3 to work. The negative DC bus in the DC bus is electrically connected to the ground terminal GND.

[0045] Specifically, the rectifier filter circuit 211 may include, but is not limited to, a rectifier bridge composed of a diode and a filter capacitor connected to the output end of the rectifier bridge. The power conversion circuit 212 includes a first transistor T1, a second transistor T2, a third transistor T3, a fourth transistor T4, a fifth transistor T5, and a sixth transistor T6. The current input end of the first transistor T1 is connected to the positive DC bus in the DC bus, and the current output end serves as the first phase voltage output end U of the inverter 21. The current input end of the second transistor T2 is connected to the current output end of the first transistor T1, and the current output end is connected to the ground terminal GND. The current input end of the third transistor T3 is connected to the positive DC bus in the DC bus, and the current output end serves as the second phase voltage output end V of the inverter 21. The current input end of the fourth transistor T4 is connected to the current output end of the third transistor T3, and the current output end is connected to the ground terminal GND. The current input end of the fifth transistor T5 is connected to the positive DC bus in the DC bus, and the current output end serves as the third phase voltage output end W of the inverter 21. The current input terminal of the sixth transistor T6 is connected to the current output terminal of the fifth transistor T5, and the current output terminal is connected to the ground terminal GND. Specifically, the first transistor T1 to the sixth transistor T6 can be IGBTs respectively.

[0046] See also Figure 3 As shown, it is a schematic diagram of the control cabinet structure provided according to some other embodiments of the present application. In some other embodiments, the control cabinet further includes a circuit breaker 23, which is connected to the voltage input terminal of the frequency converter 21. The voltage input terminal of the frequency converter 21 is correspondingly connected to the live wire of the AC power supply 1 via the circuit breaker 23. When the power supply of the AC power supply 1 is abnormal, the circuit breaker 23 is disconnected to protect the control cabinet 2 and the motor 3 from damage.

[0047] Please continue reading Figure 3 As shown, in some other embodiments, the control cabinet 2 further includes a three-phase filter circuit 24. The three-phase filter circuit 24 is connected to the voltage input end of the frequency converter 21, and the voltage input end of the frequency converter 21 is correspondingly connected to the live wire of the AC power supply 1 via the three-phase filter circuit 24, and the current drain circuit 22 is connected to the neutral line N via the three-phase filter circuit 24. The three-phase filter circuit 24 is used to filter the power supply circuit of the motor 3 to improve the power supply stability.

[0048] See also Figure 4 As shown, it is a schematic diagram of the structure of the three-phase filter circuit 24 in the control cabinet 2 provided according to some embodiments of the present application. The three-phase filter circuit 24 is provided on the three-phase live wire and the neutral wire N of the AC power supply 1, and includes a common mode inductor and a plurality of X capacitors. Specifically, each inductor coil of the common mode inductor is respectively provided on the three-phase live wire and the neutral wire N of the AC power supply 1, one end of each capacitor in the plurality of X capacitors is respectively connected to the three-phase live wire, and the other end of each capacitor in the plurality of X capacitors is respectively connected to the neutral wire N.

[0049] The input end of the three-phase filter circuit 24 includes a three-phase filter input end and a neutral filter input end PLN', and the output end of the three-phase filter circuit 24 includes a three-phase filter output end and a neutral line filter output end PLN'. The three-phase filter input end is correspondingly connected to the three-phase live wire, the neutral line filter input end PLN is connected to the neutral line N, and the three-phase filter output end is connected to the three-phase voltage input end of the inverter 21. Specifically, the three-phase filter input end includes a first phase filter input end PLa connected to the first phase live wire L1, a second phase filter input end PLb connected to the second phase live wire L2, and a second phase filter input end PL3 connected to the second phase live wire L2; the three-phase filter output end includes a first phase filter output end P l 1' connected to the first phase live wire L1, a second phase filter output end PL2' connected to the second phase live wire L2, and a third phase filter output end PL3' connected to the third phase live wire L3.

[0050] Common mode inductors can include but are not limited to Figure 4The first common mode inductor LA and the second common mode inductor LB are shown. In other embodiments, the three-phase filter circuit 24 may include only one common mode inductor or a plurality of common mode inductors, wherein the plurality of common mode inductors are connected in series between the multi-phase live wires and the neutral wire N.

[0051] Continue reading Figure 4 As shown, the multiple X capacitors of the three-phase filter circuit 24 include a first group of X capacitors and a second group of X capacitors. One end of each capacitor in the first group of X capacitors is respectively connected to the input end of each corresponding inductor coil in the common mode inductor, and the first end of each capacitor in the second group of X capacitors is respectively connected to the output end of each corresponding inductor coil in the common mode inductor. The second group of X capacitors connected to the output end of the first common mode inductor LA is equivalent to the first group of capacitors connected to the input end of the second common mode inductor LB, that is, each common mode inductor has a group of X capacitors at the input end and the output end. The first group of X capacitors connected to the input end of the first common mode inductor LA includes a first X capacitor Cx11, a second X capacitor Cx12 and a third X capacitor C13, the second group of X capacitors connected to the input end of the first common mode inductor LB includes a fourth X capacitor Cx21, a fifth X capacitor Cx22 and a sixth X capacitor C23, and the third group of X capacitors connected to the output end of the second common mode inductor LB includes a seventh X capacitor Cx31, an eighth X capacitor Cx32 and a ninth X capacitor C33.

[0052] Furthermore, in some embodiments, the current drain circuit further includes a first capacitor C1 connected between the first common-mode inductor LA and the second common-mode inductor LB and a second capacitor C2 connected to the output end of the second common-mode inductor LB, and the first capacitor C1 and the second capacitor C2 are connected in parallel between the neutral line N and the ground connection line LG where the ground terminal GND is located. The first capacitor C1 and the second capacitor C2 can be Y capacitors or multiple Y capacitors connected in series between the first terminal P1 and the second terminal P2.

[0053] Please continue reading Figure 4 As shown, the three-phase filter circuit 24 also includes a plurality of filter resistors. One end of each of the plurality of filter resistors is respectively connected to the neutral line N of each corresponding inductance line in the common mode inductor. Specifically, the filter resistors include a first filter resistor R1, a second filter resistor R2, and a third filter resistor R3 connected to the output end of the first common mode inductor LA. The first common mode inductor LA and the second common mode inductor LB are connected in series, and each filter resistor is connected between the first common mode inductor LA and the second common mode inductor LB to cooperate with the second group of X capacitors to form a low-pass channel, which is conducive to increasing the filtering effect of the multi-phase filter circuit.

[0054] In some embodiments, the three-phase filter circuit 24 and the current diversion circuit 22 can be integrated into a filter housing to form a three-phase five-wire filter, which facilitates the wiring of the circuit board in the control cabinet 2.

[0055] Furthermore, in some embodiments, the control cabinet 2 further includes a heat dissipation device, and the ground terminal GND is arranged on the heat dissipation device to provide a discharge channel for the leakage current of the inverter 21 .

[0056] In some embodiments, the present application further provides a refrigeration device, which includes a control cabinet and a fan provided in any embodiment of the present application, the ground terminal of the control cabinet is electrically connected to the fan, and the voltage output terminal of the inverter in the control cabinet is connected to the drive end of the fan. The control cabinet is used to convert the AC power output by the AC power supply into a driving voltage of the fan to control the operation of the fan and adjust the speed of the fan. The refrigeration device provided in the embodiment of the present application can achieve the same technical effect as the control cabinet provided in the embodiment of the present application, which will not be repeated here.

[0057] Furthermore, in some embodiments, the refrigeration equipment provided in the present application has multiple fans, and the metal casings of the multiple fans are respectively connected to the grounding wires of the control cabinet to lead the ground leakage current of the multiple fans to the ground back to the neutral line N through the diversion circuit in the control cabinet, thereby reducing the allowable value of the ground leakage current of the entire refrigeration equipment.

[0058] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A control cabinet, characterized in that: It includes a frequency converter, a current diversion circuit and a grounding terminal; The voltage input terminal of the frequency converter is used to be connected to the live wire of the AC power supply, and the voltage output terminal of the frequency converter is used to be connected to the driving end of the motor; The first end of the current drain circuit is electrically connected to the ground terminal, the second end of the current drain circuit is used to be connected to the neutral line of the AC power supply, and the current drain circuit is used to drain the ground leakage current to the neutral line, and the ground leakage current is generated based on the induced electromotive force on the housing of the motor; The grounding terminal is used to be electrically connected to the protective grounding wire of the AC power supply and the housing of the motor respectively.

2. The control cabinet according to claim 1, characterized in that: The current drain circuit includes a Y capacitor connected between the first end and the second end, and the ground leakage current flows to the neutral line through the Y capacitor.

3. The control cabinet according to claim 2, characterized in that: The Y capacitor includes a first Y capacitor and a second Y capacitor connected in series between the first end and the second end.

4. The control cabinet according to claim 1, characterized in that: The second end is used to be connected to a neutral line output end of a leakage protector so as to be connected to the neutral line via the leakage protector.

5. The control cabinet according to claim 1, characterized in that: The frequency converter includes a rectifier and filter circuit and a power conversion circuit; The rectifier and filter circuit is used to rectify and filter the AC power output by the AC power supply, and provide DC power to the input end of the power conversion circuit via the DC bus. The power conversion circuit is used to convert the DC power into AC power with adjustable frequency to drive the motor to work; A negative DC bus in the DC bus is electrically connected to the ground terminal.

6. The control cabinet according to claim 1, further comprising a circuit breaker; The circuit breaker is connected to the voltage input end of the frequency converter, and the voltage input end of the frequency converter is correspondingly connected to the live wire of the AC power source via the circuit breaker.

7. The control cabinet according to claim 1, further comprising a three-phase filtering circuit; The three-phase filter circuit is connected to the voltage input end of the frequency converter, and the voltage input end of the frequency converter is correspondingly connected to the live wire of the AC power supply via the three-phase filter circuit; The current drain circuit is connected to the neutral line via the three-phase filter circuit.

8. The control cabinet according to any one of claims 1 to 7, characterized in that: The motor is an external fan in a refrigeration device.

9. A refrigeration device, characterized in that: Comprising a control cabinet and a fan as claimed in any one of claims 1 to 8; The grounding terminal of the control cabinet is electrically connected to the fan, and the voltage output terminal of the frequency converter in the control cabinet is connected to the driving terminal of the fan.

10. The refrigeration device according to claim 9, characterized in that: There are multiple fans, and metal shells of the multiple fans are electrically connected to the grounding terminal of the control cabinet respectively.

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