Stacked frequency test slow start device, stacked frequency test equipment and frequency converter

Abstract

The application discloses a stacked frequency test slow starting device, a stacked frequency test equipment and a frequency converter. The device comprises a power supply subcircuit, an input end of the power supply subcircuit is connected with a power supply, wherein N is a positive integer, when N=1, the power supply subcircuit is multiplexed with a pre-charging subcircuit of a frequency conversion circuit; N power supply branches, wherein a first end of each power supply branch is connected with an output end of the power supply subcircuit, and a second end of each power supply branch is connected with a capacitor, wherein, in the case that the power supply branch is turned on, the power supply subcircuit pre-charges the corresponding capacitor through the power supply branch. The stacked frequency test slow starting device in the application arranges an additional test capacitor outside the frequency conversion circuit, so that the number of capacitor components for stacked frequency test can be flexibly configured, and at the same time, a complete power supply subcircuit can be used to pre-charge at least one capacitor component, so as to realize the multiplexing effect of the pre-charging of the frequency conversion circuit and the pre-charging of the stacked frequency test capacitor, reduce the cost, and improve the reliability of the slow starting process.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, specifically to a frequency stacking test soft start device, frequency stacking test equipment, and frequency converter. Background Technology

[0002] The asynchronous motor frequency superposition test is an indirect thermal test method for asynchronous motors, used to evaluate motor performance and characteristics. In the frequency superposition test, one or more additional frequency auxiliary power supply components are superimposed on the main power supply frequency of the motor to simulate certain conditions in actual operation. The test motor is connected between the main power supply and the auxiliary power supply, ensuring that the test motor reaches its rated current, rated voltage, and rated speed.

[0003] In current related technologies, during asynchronous motor frequency stacking tests, the DC-side support capacitor of the frequency converter needs to be configured with multiple additional frequency stacking test capacitors to maintain the stability of the DC voltage, which greatly reduces the reliability of the entire frequency stacking test when performing soft start. Utility Model Content

[0004] This application provides a frequency consolidation test soft start device, frequency consolidation test equipment, and frequency converter.

[0005] The frequency superposition test soft-start device according to the embodiments of this application performs frequency superposition tests on the target equipment through a frequency converter circuit. The DC bus of the frequency converter circuit is connected in parallel with N capacitor assemblies for frequency superposition tests. The device includes:

[0006] A power supply sub-circuit, the input terminal of which is connected to the power supply, wherein N is a positive integer. When N=1, the power supply sub-circuit reuses the pre-charge sub-circuit of the frequency converter circuit. When N>1, the power supply sub-circuit reuses or does not reuse the pre-charge sub-circuit of the frequency converter circuit.

[0007] There are N power supply branches, with the first end of each of the N power supply branches connected to the output end of the power supply sub-circuit, and the second end of each power supply branch connected to the corresponding superimposed frequency test capacitor assembly. When the power supply branch is turned on, the power supply sub-circuit precharges the corresponding superimposed frequency test capacitor assembly through the power supply branch.

[0008] Thus, the frequency stacking test soft start device in this application arranges the additional test capacitor outside the frequency converter circuit by setting up a power supply sub-circuit and at least one frequency stacking test capacitor assembly. This allows for flexible configuration of the number of frequency stacking test capacitor assemblies, while also enabling the use of a complete power supply sub-circuit to perform pre-charging and connection to the frequency converter circuit for each frequency stacking test capacitor assembly. This achieves the multiplexing effect of using a single power supply sub-circuit to connect at least one frequency stacking test capacitor assembly to realize the pre-charging of the frequency converter circuit and the pre-charging of the frequency test capacitor, reducing costs and improving the reliability of the soft start process.

[0009] In some embodiments, each of the power supply branches includes a power supply switch connected in series between the output terminal of the power supply sub-circuit and the corresponding superimposed frequency test capacitor assembly, wherein the corresponding power supply branch is turned on when the power supply switch is turned on.

[0010] In some implementations, at most one of the N power supply branches is in a conducting state at any given time.

[0011] In some embodiments, the power supply sub-circuit includes:

[0012] A power switch, wherein the first terminal of the power switch is connected to the power supply.

[0013] A rectifier circuit is provided, wherein the input terminal of the rectifier circuit is connected to the second terminal of the power switch, and the output terminal of the rectifier circuit is connected to the first terminal of each power supply branch. When the power switch is turned on, the power supply provides power to the rectifier circuit, and the rectifier circuit precharges the corresponding superimposed frequency test capacitor component through the power supply branch.

[0014] In some embodiments, the power supply subcircuit further includes a current-limiting resistor connected in series between the input terminal of the rectifier subcircuit and the second terminal of the power switch.

[0015] In some embodiments, the apparatus further includes a voltage detection subcircuit connected to each of the N superimposed frequency test capacitor assemblies and configured to detect the voltage of each superimposed frequency test capacitor assembly.

[0016] In some embodiments, each of the superimposed frequency test capacitor components is connected in series with the DC bus, wherein when the access switch is turned on, the corresponding superimposed frequency test capacitor component is connected in parallel to the DC bus.

[0017] In some embodiments, the device further includes a controller connected to the power supply subcircuit, the N power supply branches, and the access switch, and configured to control the power supply subcircuit, the N power supply branches, and the access switch.

[0018] The frequency superposition test equipment in this application includes a frequency conversion circuit and the aforementioned frequency superposition test soft start device.

[0019] The frequency converter in this application includes the above-mentioned frequency stacking test soft start device.

[0020] Additional aspects and advantages of embodiments of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of this application. Attached Figure Description

[0021] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0022] Figure 1 This is one of the circuit structure diagrams of the frequency superposition test soft start device in the embodiments of this application;

[0023] Figure 2 This is a second schematic diagram of the circuit structure of the frequency stacking test soft start device in the embodiments of this application;

[0024] Figure 3 This is a schematic diagram of the control path of the controller of the frequency stacking test soft start device in the embodiments of this application.

[0025] The components are as follows: 10. Soft start device for frequency superposition test; 11. Power supply sub-circuit; 12. Power supply branch; 13. Pre-charge sub-circuit; 20. Power supply; 30. Frequency conversion circuit; KM1. Power switch; R. Current limiting resistor; BR. Rectifier sub-circuit; KM2-1. Power switch; C1. Capacitor assembly for frequency superposition test; KM2. Access switch; KM3-1. Power switch; C2. Capacitor assembly for frequency superposition test; KM3. Access switch; KM4-1. Power switch; C3. Capacitor assembly for frequency superposition test; KM4. Access switch; KM0. Pre-charge switch; V. Voltage detection sub-circuit; C0. Support capacitor; M. Motor under test; QF1. Contact switch. Detailed Implementation

[0026] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the embodiments of this application, and should not be construed as limiting the embodiments of this application.

[0027] Please see Figure 1 The frequency superposition test soft start device 10 in this embodiment performs frequency superposition test on the target equipment through the frequency converter circuit 30. The DC bus of the frequency converter circuit 30 is connected in parallel with N capacitor assemblies for frequency superposition test. The device includes:

[0028] The power supply sub-circuit 11 has its input terminal connected to the power supply 20. N is a positive integer. When N=1, the power supply sub-circuit 11 reuses the pre-charge sub-circuit 13 of the frequency converter circuit 30. When N>1, the power supply sub-circuit 11 reuses or does not reuse the pre-charge sub-circuit 13 of the frequency converter circuit 10.

[0029] There are N power supply branches 12. The first end of each power supply branch 12 is connected to the output end of the power supply sub-circuit 11, and the second end of each power supply branch 12 is connected to the corresponding superimposed frequency test capacitor assembly. When the power supply branch 12 is turned on, the power supply sub-circuit 11 precharges the corresponding superimposed frequency test capacitor assembly through the power supply branch 12.

[0030] Specifically, please refer to Figure 1 , Figure 1 The modular schematic diagram illustrates the various components of the frequency superposition test soft start device 10. The aforementioned frequency superposition test soft start device 10 is generally used for frequency superposition testing of asynchronous motors and is used in conjunction with the frequency converter circuit 30. The frequency converter circuit 30 is connected to the power supply 20 and receives electrical energy from it; similarly, the frequency superposition test soft start device 10 is connected to the power supply 20 and receives the same electrical energy from it. The frequency converter circuit 30 generally includes a frequency converter sub-circuit and a motor M under test.

[0031] The frequency stacking test soft-start device 10 is generally divided into two parts: a power supply sub-circuit 11 and a power supply branch 12. The main function of the power supply sub-circuit 11 is to perform preliminary processing such as current limiting and rectification on the electrical energy introduced from the power supply 20, thereby processing the introduced electrical energy into a state that can be directly used to pre-charge the capacitor assembly for frequency stacking test. The power supply branch 12 is provided with N groups, where N is a positive integer. One end of each power supply branch 12 is connected to the power supply sub-circuit, and the other end is connected to a corresponding capacitor assembly for frequency stacking test. The power supply branch 12 and the corresponding capacitor assembly for frequency stacking test are connected as a whole between the power supply sub-circuit 11 and the frequency converter circuit 30. On the one hand, it receives the processed electrical energy from the power supply sub-circuit 11 to perform pre-charging on the corresponding capacitor assembly for frequency stacking test. The capacitor assembly for frequency stacking test can be a single capacitor or an equivalent capacitor combination formed by multiple capacitors connected in series, parallel or other ways. Specifically, the capacitor assembly for frequency stacking test can be represented as a capacitor cabinet.

[0032] For example, please refer to Figure 1 The situation shown is as follows: Figure 1 In the example shown, N=1, that is, a set of power supply branches 12 and a corresponding capacitor assembly C1 for frequency stacking test are provided. In addition, the power supply sub-circuit 11 is also connected to the pre-charge sub-circuit 13 of the frequency converter circuit 30. The pre-charge sub-circuit 13 includes a pre-charge access switch KM0. When the pre-charge access switch KM0 is turned on, the power supply sub-circuit 11 directly performs pre-charge on the support capacitor C0 connected to the DC bus of the frequency converter circuit 30. In this way, the power supply sub-circuit 11 is multiplexed by both the power supply branch 12 and the pre-charge sub-circuit 13 in the frequency converter circuit.

[0033] For example, please refer to Figure 2 The situation shown is as follows: Figure 2 In the example shown, N=3, where N>1. This means that there are three power supply branches 12 and corresponding capacitor components C1, C2 and C3 for frequency stacking tests. In addition, the power supply sub-circuit 11 is also connected to the pre-charge sub-circuit 13 of the frequency converter circuit 30. The pre-charge sub-circuit 13 includes a pre-charge access switch KM0. When the pre-charge access switch KM0 is turned on, the power supply sub-circuit 11 directly performs pre-charge on the support capacitor C0 connected to the DC bus of the frequency converter circuit 30. In this way, the power supply sub-circuit 11 is shared by the three power supply branches 12 and the pre-charge sub-circuit 13 in the frequency converter circuit.

[0034] In addition to the two cases mentioned above, when N>1, each power supply branch 12 can also be set independently from the pre-charge sub-circuit 13 in the frequency converter circuit. That is, the pre-charge sub-circuit 13 is directly connected to the power supply 20, while each power supply branch 12 is connected to the power supply 20 through the power supply sub-circuit 11, so that the entire assembly of each superimposed frequency test capacitor assembly and the supporting capacitor C0 can independently perform the charging process.

[0035] In other words, the frequency stacking test soft-start device 10 in this application embodiment can be configured with at least one power supply branch 12 to provide at least one frequency stacking test capacitor assembly capable of achieving the frequency stacking effect. This allows the power supply sub-circuit 11 to be reused by connecting at least one frequency stacking test capacitor assembly in a single frequency stacking test soft-start device 10, eliminating the cost of setting up a separate soft-start device for each test capacitor. Furthermore, compared to setting up a separate soft-start device for each frequency stacking test capacitor assembly, using a power supply branch 12 can effectively simplify the circuit structure for implementing the soft-start function, thereby improving the reliability of the soft-start process in frequency stacking testing.

[0036] Thus, the frequency conversion test soft start device 10 in this application arranges the additional test capacitor outside the frequency converter circuit by setting up a power supply sub-circuit 11 and at least one frequency conversion test capacitor assembly. This allows for flexible configuration of the number of frequency conversion test capacitor assemblies, while also enabling the use of a complete power supply sub-circuit 11 to perform pre-charging and connection to the frequency converter circuit 30 for each frequency conversion test capacitor assembly. This achieves the multiplexing effect of using a single power supply sub-circuit 11 to connect at least one frequency conversion test capacitor assembly to pre-charge the frequency converter circuit 30 and the frequency conversion test capacitor assembly, reducing costs and improving the reliability of the soft start process.

[0037] Please see Figure 2 In some embodiments, when N > 1, the power supply sub-circuit 11 reuses the precharge sub-circuit 13 of the frequency converter circuit 30.

[0038] Specifically, based on the above implementation, the number of power supply branch 12 and the capacitor assembly for frequency superposition testing can also be more than one, i.e., N>1. For example, please refer to... Figure 2 , Figure 2The illustrated frequency stacking test soft-start device 10 includes at least three power supply branches 12, each connected to a frequency stacking test capacitor assembly C1, C2, and C3. In this configuration, the power supply sub-circuit 11 is multiplexed by the three power supply branches 12 and the pre-charge sub-circuit 13. This allows the power supply sub-circuit 11 to achieve a "one-to-many" effect for each power supply branch 12 and the pre-charge sub-circuit 13, meaning that one power supply sub-circuit 11 can pre-charge each frequency stacking test capacitor assembly C1, C2, C3, and the supporting capacitor C0 on the bus of the frequency converter circuit 30. Compared to a separate power supply sub-circuit 11 for each frequency stacking test capacitor assembly and supporting capacitor C0, this significantly simplifies the circuit configuration. Furthermore, the on / off state of each power supply branch 12 allows for the selection and control of the current pre-charge capacitor, improving the reliability of frequency stacking test soft start through pre-charging.

[0039] Please see Figure 2 In some embodiments, each power supply branch 12 includes a power supply switch connected in series between the output terminal of the power supply sub-circuit 11 and the corresponding superimposed frequency test capacitor assembly, wherein when the power supply switch is turned on, the corresponding power supply branch 12 is turned on.

[0040] In some implementations, at most one of the N power supply branches 12 is in a conducting state at any given time.

[0041] For details, please continue reading Figure 2 Based on the above implementation, the power supply branch 12 includes a power supply switch, which is connected in series between the output terminal of the power supply sub-circuit 11 and the superposition test capacitor assembly corresponding to its power supply branch 12. For example, with Figure 2 Taking the capacitor component C2 used for superposition frequency testing as an example, its corresponding power supply branch 12 includes the power supply switch KM3-1. For example, taking... Figure 2 Taking the capacitor component C3 used for superposition frequency testing as an example, its corresponding power supply branch 12 includes power supply switch KM4-1, etc.

[0042] The aforementioned power switch controls the on / off state of the corresponding power supply branch 12. Its main function is to control the start and stop of the pre-charging process of the corresponding superimposed frequency test capacitor assembly by controlling the on / off state of the power supply branch 12. When the power switch is on, the corresponding power supply branch 12 is on, and the power supply sub-circuit 11 performs pre-charging on the superimposed frequency test capacitor assembly corresponding to the power supply branch 12. Conversely, when the power switch is off, the corresponding power supply branch 12 is off, and the pre-charging process performed by the power supply sub-circuit 11 on the superimposed frequency test capacitor assembly corresponding to the power supply branch 12 ends.

[0043] Furthermore, in the case of multiple power supply branches 12 in the frequency conversion test soft start device, each power supply branch 12 is connected in parallel between the power supply sub-circuit 11 and the frequency converter circuit 30. It is also necessary to ensure that within the range of each frequency conversion test capacitor component, only one frequency conversion test capacitor component is performing pre-charging at any given time. Therefore, correspondingly, within the range of all power supply branches 12, at most one power supply switch is allowed to be closed at any given time. For example, using... Figure 2 Taking the scenario shown as an example, within the range of capacitor components C1, C2, and C3 for frequency superposition testing, at most one capacitor component can perform pre-charging at any given time. Therefore, within the range of power supply switches KM2-1, KM3-1, and KM4-1, at most one of them can be closed at any given time, corresponding to at most one of the three power supply branches 12 being turned on at any given time. When one of the three power supply branches 12 is turned on, the other two power supply branches 12 must remain open. If multiple sets of power supply switches are closed simultaneously, the parallel connection of multiple capacitor components for frequency superposition testing will increase the equivalent capacitance of the entire circuit performing charging, thereby increasing the voltage during the pre-charging process. Due to the characteristics of parallel circuits, the voltage across each capacitor component for frequency superposition testing increases, thus threatening the electrical safety of the capacitor components during the pre-charging process.

[0044] In some embodiments, the power supply sub-circuit 11 includes:

[0045] Power switch KM1, the first terminal of power switch KM1 is connected to power supply 20;

[0046] The input terminal of the rectifier circuit BR is connected to the second terminal of the power switch KM1, and the output terminal of the rectifier circuit BR is connected to the first terminal of each power supply branch 12. When the power switch KM1 is turned on, the power supply 20 supplies power to the rectifier circuit BR, and the rectifier circuit BR precharges the corresponding stacked frequency test capacitor component through the power supply branch 12.

[0047] For details, please continue reading Figure 2For example, the power supply sub-circuit 11 in the frequency stacking test soft start device 10 includes at least a power switch KM1 and a rectifier sub-circuit BR. The power switch KM1 mainly acts as the main switch of the frequency stacking test soft start device 10 and the switch of the power supply sub-circuit 11. When the power switch KM1 is closed, the frequency stacking test soft start device 10 is directly connected to the power supply 20, thereby preparing for the pre-charging of each frequency stacking test capacitor component. When the power switch KM1 is open, the frequency stacking test soft start device 10 is disconnected from the power supply 20. The above-mentioned disconnection from the power supply 20 corresponds to two states of the frequency stacking test soft start device 10: one is when it is stopped from running, and the other is when the frequency stacking test capacitor components are connected to the frequency converter circuit 30 after the pre-charging of the frequency stacking test capacitor components is completed. The purpose of disconnecting the power switch KM1 in the latter case is to ensure that when the frequency stacking test capacitor components are connected to the frequency converter circuit 30, additional current is avoided from being introduced into the frequency converter circuit 30, thereby avoiding negative impacts on the normal operation of the frequency converter circuit 30 and the frequency stacking test process.

[0048] As a further example, the rectifier circuit BR described above is generally composed of multiple diodes. Figure 2 The illustrated configuration shows the rectifier circuit BR setup when the power supply 20 is a three-phase AC circuit. In the example above, the rectifier circuit BR is divided into three branches. With the power switch KM1 closed, each branch is connected to one phase of the power supply 20, and the connection point on each branch is located between two diodes with identical anode and cathode arrangements connected in series. The purpose of this arrangement is to rectify the alternating current introduced from the power supply 20 to obtain the DC current required for charging the capacitor assembly used in the frequency superposition test. Please refer to [link to relevant documentation]. Figure 2 ,exist Figure 2 In the rectifier circuit BR shown, after the current passes through the rectifier circuit BR, due to the unidirectional conductivity of the diode, the current only flows out from the top end of the rectifier circuit BR, that is, the current output from the rectifier circuit BR is a direct current.

[0049] Please see Figure 2 In some embodiments, the power supply sub-circuit 11 further includes a current-limiting resistor R, which is connected in series between the input terminal of the rectifier sub-circuit BR and the second terminal of the power switch KM1.

[0050] Specifically, based on the above implementation method, since the voltage and current of the power supply 20 may both be at high levels in practical applications, directly introducing electrical energy from the power supply 20 and rectifying it solely through the rectifier circuit BR cannot significantly affect its voltage and current. To ensure the electrical safety of each component during the pre-charging process of the capacitor assembly for frequency superposition testing, the power supply sub-circuit 11, exemplarily, also includes a current-limiting resistor R. Please refer to... Figure 2 ,exist Figure 2 In the example shown, the current-limiting resistor R is connected between the power switch KM1 and the rectifier circuit BR. Its main function is to limit the impact of surge current on the frequency superposition test capacitor component corresponding to power supply branch 12 and the pre-charging process. Taking the power supply branch 12 corresponding to the frequency superposition test capacitor component C1 as an example, if the aforementioned current-limiting resistor R is not set, when the device is first powered on or at the moment of conduction of each half-cycle of AC power, the frequency superposition test capacitor component C1 is generally in an uncharged state (approximately a short-circuit state). At this time, if the introduced AC power is 380V three-phase AC power, the peak voltage output of the rectifier circuit BR will be approximately 537V. Such a voltage applied directly to the frequency superposition test capacitor component C1 will generate an instantaneous charging current approaching infinity. The frequency superposition test capacitor component C1 is very likely to be burned out by the instantaneous large current. When a current-limiting resistor R is set, according to Ohm's law, with the peak voltage remaining constant, the peak value of the instantaneous charging current is inversely proportional to the resistance value of the current-limiting resistor R. That is, the current-limiting resistor R effectively limits the instantaneous charging current, thereby protecting the rectifier circuit BR and the capacitor component C1 used for frequency superposition testing, preventing them from burning out due to large current surges. Furthermore, according to... Figure 2 As shown, the current-limiting resistor R is set on the AC side of the frequency stacking test soft start device 10. Due to its voltage division effect, the DC voltage obtained after rectification by the rectifier circuit BR when the frequency stacking test capacitor component C1 is pre-charged will be slightly lower than the peak voltage mentioned above. That is, the current-limiting resistor R can adjust the charging voltage of the frequency stacking test capacitor component C1 by voltage division.

[0051] Furthermore, the current-limiting resistor R can also protect the operating state of the rectifier circuit BR. When the AC current input to the power supply 20 is reversed (e.g., during the switching between positive and negative half-cycles), the reverse recovery process of the diodes in the rectifier circuit BR may generate high-frequency oscillating current. The presence of the current-limiting resistor R can provide damping for such oscillation signals, thereby reducing electromagnetic interference or lowering the frequency of voltage spikes, and thus protecting the operating state of the rectifier circuit BR.

[0052] In some embodiments, the frequency stacking test soft start device 10 further includes a voltage detection sub-circuit V, which is connected to each of the N frequency stacking test capacitor assemblies and is configured to detect the voltage of each frequency stacking test capacitor assembly.

[0053] Specifically, please refer to Figure 2Based on the above embodiments, exemplarily, each of the capacitor components C1, C2, and C3 used for frequency stacking tests is connected to a corresponding voltage testing sub-circuit V at both ends. The voltage testing sub-circuit V can be a voltmeter, multimeter, or other measuring device that can be used to measure the voltage between two points in a circuit. During the pre-charging process, the user can monitor the voltage across the capacitor components of the frequency stacking tests in real time through the voltage testing sub-circuit V. When the measurement result of the voltage testing sub-circuit V determines that the pre-charging of the corresponding capacitor component of the frequency stacking tests is complete, the user can control the corresponding power supply switch to disconnect to end the pre-charging process. At the same time, during the pre-charging process and during the process of the corresponding capacitor component of the frequency stacking tests being connected to the frequency converter circuit 30 to perform frequency stacking tests, the user can also monitor the pre-charging process or the frequency stacking test process in real time by checking the measurement result of the voltage testing sub-circuit V at any time, so as to deal with potential faults at any time and improve the reliability of the frequency stacking test soft start device 10 and the frequency converter circuit 30.

[0054] Please see Figure 2 In some embodiments, each capacitor assembly for frequency stacking test is connected in series with the DC bus, wherein when the connection switch is turned on, the corresponding capacitor assembly for frequency stacking test is connected in parallel to the DC bus.

[0055] For details, please continue reading Figure 2 Based on the above implementation method, each set of capacitor components for frequency stacking test is also connected to an access switch. The main function of the access switch is to connect the capacitor components for frequency stacking test to or disconnect them from the busbars of the frequency converter circuit 30 by switching them on and off.

[0056] For example, with Figure 2 Taking the capacitor assembly C2 used for frequency superposition testing as an example, switch KM3 is connected between the capacitor assembly C2 and the busbar of the frequency converter circuit 30. For another example... Figure 2 Taking the capacitor assembly C3 for frequency stacking test as an example, the switch KM4 is connected between the capacitor assembly C3 for frequency stacking test and the bus of the frequency converter circuit 30.

[0057] Based on the above implementation method, the main function of the power supply switch is to control the start and stop of the pre-charging process of the capacitor assembly for the frequency superposition test. To achieve this function, it needs to cooperate with the power switch KM1 and the access switch. If the power switch KM1 is open, the pre-charging of the capacitor assembly for the frequency superposition test cannot be performed. The main function of the access switch is to connect the pre-charged capacitor assembly for the frequency superposition test to the frequency converter circuit 30. As described in the above implementation method, in order to avoid introducing additional DC current into the frequency converter circuit 30 when connected to it, and to ensure the normal execution of the frequency superposition test, it is necessary to ensure that the current used for pre-charging is not input into the frequency converter circuit 30 when the capacitor assembly for the frequency superposition test is connected to it. Therefore, the corresponding power supply switch must be kept in the open state when the access switch is closed.

[0058] Next Figure 2 Taking the power supply branch 12, where the capacitor assembly C1 for the frequency conversion test is located, as an example, the pre-charging process and the control flow of the frequency converter circuit 30 are explained in detail: When the power switch KM1 is closed, the power supply switch KM2-1 is closed, while the connection switch KM2 remains open. At this time, the capacitor assembly C1 for the frequency conversion test is connected to both ends of the rectifier circuit BR. The alternating current introduced from the power supply 20 is rectified into DC current by the rectifier circuit BR through the power switch KM1 and the current limiting resistor R. Then, the DC current is applied to both ends of the capacitor assembly C1 for the frequency conversion test through the power supply switch KM2-1, and the capacitor assembly C1 for the frequency conversion test is in a pre-charging state. When it is necessary to control the end of the pre-charging state, while keeping the connection switch KM2 open, the power supply switch KM2-1 is opened. At this time, the capacitor assembly C1 for the frequency conversion test is disconnected from both ends of the rectifier circuit BR, and the pre-charging process ends. In addition, to ensure electrical safety, the power switch KM1 can be turned off when the power supply switch KM2-1 is turned off, so as to ensure the overall electrical safety of the frequency stacking test soft start device 10.

[0059] Furthermore, after disconnecting the power supply switch KM2-1 to control the end of the pre-charging process, the power supply switch KM2-1 remains open while the control switch KM2 is closed. At this time, the capacitor assembly C1 for the frequency superposition test is connected between the two buses of the frequency converter circuit 30 to act as a bus capacitor with a frequency superposition effect during the frequency superposition test. In this process, in order to ensure that no other current is introduced when the capacitor assembly C1 for the frequency superposition test is connected to the frequency converter circuit 30, optionally, the power supply switch KM1 is closed first before closing the control switch KM2 to avoid introducing additional current into the frequency converter circuit 30 in extreme cases where the power supply switch KM2-1 remains closed due to a failure, thus ensuring the smooth execution of the frequency superposition test.

[0060] Please see Figure 3 In some embodiments, the device further includes a controller 40, which is connected to the power supply subcircuit 11, the N power supply branches 12 and the access switch, and is configured to control the power supply subcircuit 11, the N power supply branches 12 and the access switch.

[0061] Specifically, based on the above embodiments, the frequency superposition test soft start device 10 is exemplarily provided with a controller 40, whose main function is to control the on / off state of the power supply sub-circuit 11, each power supply branch 12, and the access switch in the above embodiments. Specifically, the controller 40 indirectly controls the on / off state of the power supply sub-circuit 11 and each power supply branch 12 by directly controlling the on / off state switching of the power switch KM1 and each power supply switch KM2-1, KM3-1, and KM4-1.

[0062] In addition, based on the above implementation, the pre-charge access switch KM0 included in the pre-charge sub-circuit 13 of the frequency converter circuit 30 is also controlled by the controller 40. When the pre-charge access switch KM0 is turned on, the power supply sub-circuit 11 directly performs pre-charge on the support capacitor C0 connected to the DC bus of the frequency converter circuit 30. To ensure that the voltage across the support capacitor C0 is not disturbed during pre-charge, when the contact switch QF1 in the frequency converter circuit 30 is open, the power switch KM1 and the pre-charge access switch KM0 are closed. At this time, the support capacitor C0 is connected across the rectifier sub-circuit BR and is pre-charged by the DC current introduced and processed by the power supply sub-circuit 11. After the above pre-charge process is completed, the pre-charge access switch KM0 is turned off. Optionally, for the sake of ensuring the power safety of the frequency stacking test soft start device 10, the power switch KM1 is also turned off when the pre-charge access switch KM0 is turned off. Then, the frequency converter circuit 30 can be started by closing the contact switch QF1, thereby starting the soft start process of the frequency stacking test.

[0063] Therefore, regarding the slow-start process of the superposition test executed by the superposition test slow-start device 10 described above, please refer to [reference needed]. Figure 2 The circuit structure shown is executed according to the following flowchart example. It should be noted that the on / off control of power switch KM1 can be adjusted according to actual conditions, as long as the on / off state of power switch KM1 meets the requirements of the corresponding steps:

[0064] ① Before the frequency stacking test begins, in the initial state, keep the power switch KM1, all power supply switches, all access switches, precharge access switch KM0, and the contact switch QF1 of the frequency converter circuit 30 all open.

[0065] ② Close the power switch KM1 and the pre-charge access switch KM0 to pre-charge the supporting capacitor C0 in the frequency converter circuit 30. After pre-charging is completed, open the pre-charge access switch KM0 and close the contact switch QF1 of the frequency converter circuit 30.

[0066] ③ With power switch KM1 closed, close power supply switch KM2-1 while keeping connection switch KM2 open to perform pre-charging on the frequency conversion test capacitor assembly C1. After the frequency conversion test capacitor assembly C1 has completed pre-charging, open power supply switch KM2-1, close connection switch KM2, and connect the pre-charged frequency conversion test capacitor assembly C1 to the busbars of frequency converter circuit 30.

[0067] ④ With power switch KM1 closed, close power supply switch KM3-1 while keeping connection switch KM3 open to precharge the capacitor assembly C2 for frequency consolidation testing. After precharging of capacitor assembly C2 for frequency consolidation testing is complete, disconnect power supply switch KM3-1, close connection switch KM3, and connect the precharged capacitor assembly C2 for frequency consolidation testing to the busbars of frequency converter circuit 30.

[0068] ⑤ With power switch KM1 closed, close power supply switch KM4-1 and keep connection switch KM4 open to pre-charge the capacitor assembly C3 for frequency conversion testing. After the pre-charging of capacitor assembly C3 for frequency conversion testing is complete, open power supply switch KM4-1, close connection switch KM4, and connect the pre-charged capacitor assembly C3 for frequency conversion testing to the busbars of frequency converter circuit 30.

[0069] ⑥ Finally, keep the power switch KM1 off to avoid introducing additional current into the frequency converter circuit 30 when the capacitor assembly for the frequency conversion test is connected to the bus of the frequency converter circuit 30, thereby avoiding interference with the frequency conversion test process.

[0070] Steps ② to ⑤ above constitute the soft start process of the entire frequency stacking test. The execution order of steps ③ to ⑤ can be arbitrarily changed. The above order is only an example and should not be construed as a limitation.

[0071] The frequency superposition test equipment in this application includes a frequency conversion circuit 30 and the aforementioned frequency superposition test soft start device 10.

[0072] Please refer to details. Figure 2 , Figure 2The intermediate frequency converter circuit 30 includes a motor under test (M) and a frequency converter sub-circuit connected to the motor under test (M). The frequency converter sub-circuit is connected to the power supply 20, and the main switch is a contact switch QF1. The three phases connected to the frequency converter circuit 30 are respectively connected to points A, B, and C in the rectifier transistor group of the frequency converter sub-circuit. The motor under test (M) is generally an asynchronous motor, and its three input terminals are respectively connected to points U, V, and W in the inverter transistor group of the frequency converter sub-circuit. A support capacitor C0, a pre-charge sub-circuit 13, and the access switches of the frequency stacking test soft start device 10 are connected at the bus between the rectifier transistor group and the inverter transistor group. The main function of the support capacitor C0 is to stabilize the DC voltage and absorb energy fluctuations; its working state directly affects the performance and reliability of the frequency converter. The frequency converter circuit 30 and the frequency stacking test soft start device 10 in the above embodiment together constitute the frequency stacking test equipment for performing frequency stacking tests.

[0073] The frequency converter in this application includes the above-mentioned frequency stacking test soft start device 10.

[0074] In the description of this specification, the references to terms such as "some embodiments," "in one example," "exemplarily," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0075] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order according to the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0076] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A soft-start device for frequency superposition testing, characterized in that, The target equipment is subjected to superposition frequency testing via a frequency converter circuit. The DC bus of the frequency converter circuit is connected in parallel with N capacitor assemblies for superposition frequency testing. The device includes: A power supply sub-circuit, the input terminal of which is connected to the power supply, wherein N is a positive integer. When N = 1, the power supply sub-circuit reuses the pre-charge sub-circuit of the frequency converter circuit. When N > 1, the power supply sub-circuit reuses or does not reuse the pre-charge sub-circuit of the frequency converter circuit. There are N power supply branches, with the first end of each of the N power supply branches connected to the output end of the power supply sub-circuit, and the second end of each power supply branch connected to the corresponding superimposed frequency test capacitor assembly. When the power supply branch is turned on, the power supply sub-circuit precharges the corresponding superimposed frequency test capacitor assembly through the power supply branch.

2. The frequency superposition test soft-start device according to claim 1, characterized in that, Each of the power supply branches includes a power supply switch connected in series between the output terminal of the power supply sub-circuit and the corresponding superimposed frequency test capacitor assembly, wherein the corresponding power supply branch is turned on when the power supply switch is turned on.

3. The frequency superposition test soft-start device according to claim 1 or 2, characterized in that, At any given time, at most one of the N power supply branches is in a conducting state.

4. The frequency superposition test soft-start device according to claim 1, characterized in that, The power supply sub-circuit includes: A power switch, wherein the first terminal of the power switch is connected to the power supply. A rectifier circuit is provided, wherein the input terminal of the rectifier circuit is connected to the second terminal of the power switch, and the output terminal of the rectifier circuit is connected to the first terminal of each power supply branch. When the power switch is turned on, the power supply provides power to the rectifier circuit, and the rectifier circuit precharges the corresponding superimposed frequency test capacitor component through the power supply branch.

5. The frequency superposition test soft-start device according to claim 4, characterized in that, The power supply sub-circuit also includes a current-limiting resistor, which is connected in series between the input terminal of the rectifier sub-circuit and the second terminal of the power switch.

6. The frequency superposition test soft-start device according to claim 1, characterized in that, The device further includes a voltage detection sub-circuit, which is connected to each of the N superimposed frequency test capacitor assemblies and is configured to detect the voltage of each superimposed frequency test capacitor assembly.

7. The frequency superposition test soft-start device according to claim 1, characterized in that, Each of the superimposed frequency test capacitor components is connected in series with the DC bus, wherein when the access switch is turned on, the corresponding superimposed frequency test capacitor component is connected in parallel to the DC bus.

8. The frequency superposition test soft-start device according to claim 7, characterized in that, The device further includes a controller connected to the power supply subcircuit, the N power supply branches, and the access switch, and configured to control the power supply subcircuit, the N power supply branches, and the access switch.

9. A frequency superposition test device, characterized in that, The frequency convolution test equipment includes a frequency conversion circuit and a frequency convolution test soft start device as described in any one of claims 1-8.

10. A frequency converter, characterized in that, The frequency converter includes the frequency stacking test soft start device as described in any one of claims 1-8.

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