A control circuit for live plug-in busbars

Abstract

The application discloses a control circuit of a live plug-in female bus, and relates to the technical field of power electronics. The control circuit comprises a first pre-charging switch, a first main switch, a first resistor, a second resistor and a fuse knife switch. The first input end of the first pre-charging switch and the first input end of the first main switch are connected to the first output end of the fuse knife switch, the second input end of the first pre-charging switch and the second input end of the first main switch are connected to the second output end of the fuse knife switch, and the input end of the fuse knife switch is connected to the female bus. When power needs to be provided to a motor, the first pre-charging switch is closed, the motor inverter is pre-charged through the first pre-charging switch, the first resistor and the second resistor reduce the initial input current of the inverter, when the pre-charging reaches a set time length, the first main switch is closed, and the first pre-charging switch is disconnected, and the motor is driven to work through the first main switch. The application solves the problem that the motor cannot be directly live plugged into a high-voltage direct-current female bus.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a control circuit for hot-plugging busbars. Background Technology

[0002] Currently, most cold rolling processing line drive systems use the Siemens S120 system. This system is mostly designed with a common DC bus, that is, the three-phase input (380V-440VAC) is converted into DC (540V-600VDC) by a rectifier and transmitted to the busbar on the top of the drive cabinet. The busbar is converted into AC by an inverter and then output to each variable frequency motor on site. The motor drives the transmission equipment to achieve the purpose of continuous production on the production line.

[0003] Each drive motor is controlled by one or more inverters, with a large number of book-type inverters. These inverters are connected to the DC bus via fuse switches. If the equipment or the inverter itself malfunctions, the fuse switches need to be de-energized (physical isolation) for troubleshooting or equipment replacement. After the equipment is repaired, the circuit breaker needs to be re-energized. At this time, the rectifier needs to be de-energized, otherwise the fuse switches will burn out (due to the effect of the internal capacitor of the inverter, the instantaneous current is particularly large at the moment of closing). After the rectifier is de-energized, all inverters connected to the DC bus will not be able to work properly, affecting the normal operation of the production line.

[0004] Therefore, the main problem with the original DC-AC system design was that it could not achieve live plugging and unplugging of the DC busbar. Summary of the Invention

[0005] The purpose of this invention is to provide a control circuit for hot-plugging busbars to solve the technical problem in the prior art that DC busbars cannot be directly hot-plugged.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] One aspect of this invention provides a control circuit for hot-swappable busbars. The control circuit includes: a first pre-charge switch, a first main switch, a first resistor, and a second resistor. A first input terminal of the first pre-charge switch is connected to a first input terminal of the first main switch, and a second input terminal of the first pre-charge switch is connected to a second input terminal of the first main switch. A first output terminal of the first pre-charge switch is connected to a first output terminal of the first main switch and a first electrode of a load via the first resistor, and a second output terminal of the first pre-charge switch is connected to a second output terminal of the first main switch and a second electrode of the load via the second resistor. A fuse is also provided. The first input terminal of the switch and the first input terminal of the first main switch are connected to the first output terminal of the fuse switch. The second input terminal of the first pre-charge switch and the second input terminal of the first main switch are connected to the second output terminal of the fuse switch. The input terminal of the fuse switch is connected to the busbar. When the fuse switch is closed, both the first pre-charge switch and the first main switch are in the open state. When power needs to be supplied to the load, the first pre-charge switch is closed to pre-charge the load. When the pre-charge reaches the set time, the first main switch is closed and the first pre-charge switch is opened, and the load is driven to work through the first main switch.

[0008] In some embodiments, the first pre-charge switch is a first pre-charge relay. One end of the first controlled terminal of the first pre-charge relay is connected to the first input terminal of the first main switch, and one end of the second controlled terminal of the first pre-charge relay is connected to the second input terminal of the first main switch. The other end of the first controlled terminal of the first pre-charge relay is connected to the first output terminal of the first main switch and the first electrode of the load through the first resistor. The other end of the second controlled terminal of the first pre-charge relay is connected to the second output terminal of the first main switch and the second electrode of the load through the second resistor. The control circuit further includes a second pre-charge relay and a control unit. The control unit is connected to both ends of the control terminal of the second pre-charge relay. One end of the controlled terminal of the second pre-charge relay is connected to one end of the power supply, and the other end of the controlled terminal of the second pre-charge relay is connected to the other end of the power supply through the control terminal of the first pre-charge relay.

[0009] In some embodiments, the first main switch is a first main relay. One end of the first controlled terminal of the first pre-charge relay is connected to one end of the first controlled terminal of the first main relay. One end of the second controlled terminal of the first pre-charge relay is connected to one end of the second controlled terminal of the first main relay. The other end of the first controlled terminal of the first pre-charge relay is connected to the other end of the first controlled terminal of the first main relay and the first electrode of the load through the first resistor. The other end of the second controlled terminal of the first pre-charge relay is connected to the other end of the second controlled terminal of the first main relay and the second electrode of the load through the second resistor. The control circuit further includes a second main relay. The control unit is connected to both ends of the control terminal of the second main relay. One end of the controlled terminal of the second main relay is connected to one end of the power supply. The other end of the controlled terminal of the second main relay is connected to one end of the third controlled terminal of the first pre-charge relay and one end of the third controlled terminal of the first main relay. The other end of the control terminal of the first main relay is connected to the other end of the power supply.

[0010] In some embodiments, the control unit includes a first AND gate, a first NOT gate, and a control module. The first input of the first AND gate is connected to a frequency converter, the second input of the first AND gate is connected to the output of the first NOT gate, the input of the first NOT gate is connected to the output of the control module, the input of the control module is connected to the frequency converter, the output of the control module is connected to the control terminal of the second main relay, and the output of the first AND gate is connected to the control terminal of the second pre-charge relay.

[0011] In some embodiments, the control module includes a second AND gate and a first comparator. The first input of the first comparator is connected to the charging voltage of the detected load, and the second input of the first comparator is connected to a first reference voltage. The first input of the second AND gate is connected to a frequency converter, and the second input of the second AND gate is connected to the first output of the first comparator. The output of the second AND gate is connected to the control terminal of the second main relay, and the output of the second AND gate is connected to the second input of the first AND gate through the first NOT gate.

[0012] In some embodiments, the control unit further includes a shutdown delay circuit, wherein the first input terminal of the first AND gate is connected to the frequency converter through the shutdown delay circuit, and the first input terminal of the second AND gate is connected to the frequency converter through the shutdown delay circuit.

[0013] In some embodiments, the control unit further includes a pulse hold circuit, wherein the first input terminal of the first AND gate is connected to the output terminal of the turn-off delay circuit and the first input terminal of the second AND gate through the pulse hold circuit, and the input terminal of the turn-off delay circuit is connected to the frequency converter.

[0014] In some embodiments, the control unit further includes a first turn-on delay circuit, and the output of the second AND gate is connected to the first NOT gate through the first turn-on delay circuit.

[0015] In some embodiments, the control module further includes a second turn-on delay circuit, wherein the second input terminal of the second AND gate is connected to the first output terminal of the first comparator through the second turn-on delay circuit.

[0016] In some embodiments, the control module further includes a second comparator and a second NOT gate. The first input terminal of the second comparator is connected to the voltage of the detection busbar, the second input terminal of the second comparator is connected to a second reference voltage, and the second output terminal of the second comparator is connected to the third input terminal of the second AND gate through the second NOT gate.

[0017] According to an embodiment of the present invention, a control circuit for a live plug-in busbar has at least the following beneficial effects: When the fuse switch is closed, both the first pre-charge switch and the first main switch are in the open state. When power needs to be supplied to the motor, the first pre-charge switch is closed, and the capacitor inside the motor inverter is pre-charged through the first pre-charge switch. The first resistor and the second resistor reduce the initial input current of the inverter when the first pre-charge switch is closed. When the pre-charge reaches a set time and the inverter charge exceeds a first reference voltage value, the first main switch is closed, and the first pre-charge switch is delayed before being opened, allowing the motor to operate through the first main switch. This ensures that the motor can be smoothly reconnected and restored after repairs, guaranteeing the stable operation of the production line. Simultaneously, it achieves physical isolation during maintenance, ensuring safety and ensuring that the inverter equipment can be powered on and off without interruption during maintenance and abnormal situations, saving manpower and time, and reducing the workload of maintenance personnel.

[0018] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this disclosure. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the control circuit for hot-plugging busbars according to an embodiment;

[0021] Figure 2 This is a logic block diagram of the control unit according to an embodiment.

[0022] The reference numerals in the attached diagram are explained as follows: 1. First AND gate; 2. First NOT gate; 3. Second AND gate; 4. Second NOT gate; 5. First comparator; 6. Turn-off delay circuit; 7. Pulse hold circuit; 8. First turn-on delay circuit; 9. Second turn-on delay circuit; 10. Second comparator; 100. Control unit. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection," "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that the description of this disclosure will be more complete and fully convey the concept of the exemplary embodiments to those skilled in the art. The drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0027] The technical solutions of the embodiments of this application are briefly described below:

[0028] According to some embodiments, such as Figure 1 As shown, this application provides a control circuit for hot-plugging a busbar, the control circuit comprising:

[0029] The system comprises a first pre-charge switch, a first main switch, a first resistor R1, and a second resistor R2. The first input terminal of the first pre-charge switch is connected to the first input terminal of the first main switch, and the second input terminal of the first pre-charge switch is connected to the second input terminal of the first main switch. The first output terminal of the first pre-charge switch is connected to the first output terminal of the first main switch and the first electrode of the load through the first resistor R1, and the second output terminal of the first pre-charge switch is connected to the second output terminal of the first main switch and the second electrode of the load through the second resistor R2.

[0030] The fuse switch FU has its first input terminal of the first pre-charge switch and the first input terminal of the first main switch connected to its first output terminal, its second input terminal of the first pre-charge switch and the second input terminal of the first main switch connected to its second output terminal, and its input terminal connected to the busbar.

[0031] When the fuse switch FU is closed, both the first pre-charge switch and the first main switch are in the open state. When power needs to be supplied to the load, the first pre-charge switch is closed to pre-charge the load. When the pre-charge reaches the set time, the first main switch is closed and the first pre-charge switch is opened, and the load is driven to work through the first main switch.

[0032] The working principle based on the above embodiments is as follows: In some embodiments of this application, the busbar adopts a DC 600V DC busbar. When the fuse switch FU is closed, both the first pre-charge switch and the first main switch are in the open state, and no current flows. Therefore, the load and the fuse switch FU are not affected. In some embodiments of this application, the load is an AC motor, which includes an inverter and a motor body. The first input terminal of the inverter serves as the first electrode of the load, and the second input terminal of the inverter serves as the second electrode of the load, for receiving power output from the first pre-charge switch or the first main switch. The inverter converts the input DC power into AC power and outputs it to the motor body to drive the motor body.

[0033] Furthermore, when power needs to be supplied to the inverter, the first pre-charge switch is closed to pre-charge the capacitors in the inverter. During pre-charging, the first resistor R1 and the second resistor R2 limit the current and voltage of the inverter to prevent excessive current and voltage from burning out the fuse FU. When the pre-charging reaches the set time, the capacitors in the inverter are charged to a level above the first reference voltage V1. At this point, the first main switch is closed, and the first pre-charge switch is opened after a delay, driving the motor body to operate through the first main switch. The set time can be set according to the first reference voltage V1, which can be set according to actual needs. The first reference voltage V1 is not significantly different from the DC 600V of the DC bus, so that the current change is small when the first main switch is turned on, protecting the fuse FU from burning out.

[0034] The following is in conjunction with the appendix to this instruction manual. Figures 1 to 2 The preferred embodiments of this disclosure will be further described in detail below.

[0035] According to some embodiments, such as Figure 1 As shown, the first pre-charge switch uses a first pre-charge relay K11. One end of the first controlled terminal of the first pre-charge relay K11 is connected to the first input terminal of the first main switch, and one end of the second controlled terminal of the first pre-charge relay K11 is connected to the second input terminal of the first main switch. The other end of the first controlled terminal of the first pre-charge relay K11 is connected to the first output terminal of the first main switch and the first electrode of the load through the first resistor R1. The other end of the second controlled terminal of the first pre-charge relay K11 is connected to the second output terminal of the first main switch and the second electrode of the load through the second resistor R2.

[0036] The control circuit also includes a second pre-charge relay K12 and a control unit 100. The control unit 100 is connected to both ends of the control terminal of the second pre-charge relay K12. One end of the controlled terminal of the second pre-charge relay K12 is connected to one end of the power supply, and the other end of the controlled terminal of the second pre-charge relay K12 is connected to the other end of the power supply through the control terminal of the first pre-charge relay K11.

[0037] Furthermore, the first main switch adopts a first main relay K21. One end of the first controlled terminal of the first pre-charge relay K11 is connected to one end of the first controlled terminal of the first main relay K21. One end of the second controlled terminal of the first pre-charge relay K11 is connected to one end of the second controlled terminal of the first main relay K21. The other end of the first controlled terminal of the first pre-charge relay K11 is connected to the other end of the first controlled terminal of the first main relay K21 and the first electrode of the load through the first resistor R1. The other end of the second controlled terminal of the first pre-charge relay K11 is connected to the other end of the second controlled terminal of the first main relay K21 and the second electrode of the load through the second resistor R2.

[0038] The control circuit further includes a second main relay K22. The control unit 100 is connected to both ends of the control terminal of the second main relay K22. One end of the controlled terminal of the second main relay K22 is connected to one end of the power supply. The other end of the controlled terminal of the second main relay K22 is connected to one end of the third controlled terminal of the first pre-charge relay K11 and one end of the third controlled terminal of the first main relay K21. The other end of the third controlled terminal of the first pre-charge relay K11 and the other end of the third controlled terminal of the first main relay K21 are both connected to one end of the control terminal of the first main relay K21. The other end of the control terminal of the first main relay K21 is connected to the other end of the power supply.

[0039] The control unit 100 receives a DC 24V power supply, and the control terminals (coil terminals) of the first pre-charge relay K11 and the first main relay K21 receive an AC 220V power supply.

[0040] The working principle of the above embodiment is as follows: when power needs to be supplied to the inverter, the control unit 100 outputs power to energize the control terminal (coil terminal) of the second pre-charge relay K12, causing the second pre-charge relay K12 to engage. This energizes the control terminal (coil terminal) of the first pre-charge relay K11, causing the first pre-charge relay K11 to engage. The capacitor in the inverter then begins pre-charging through the first and second controlled terminals of the first pre-charge relay K11. The first resistor R1 and the second resistor R2 limit the current and voltage of the inverter during pre-charging to prevent excessive current and voltage from causing the fuse FU to burn out.

[0041] When the pre-charging reaches the set time and the capacitor in the inverter is charged to a level above the first reference voltage V1, the control unit 100 outputs power to energize the control terminal (coil terminal) of the second main relay K22, causing the second main relay K22 to engage. This energizes the control terminal (coil terminal) of the first main relay K21, causing the first main relay K21 to engage and self-lock. After the first main relay K21 engages and self-locks, the control unit 100 stops supplying power to the control terminal (coil terminal) of the second pre-charging relay K12, causing the controlled terminal of the second pre-charging relay K12 to disconnect. The control terminal (coil terminal) of the first pre-charging relay K11 is de-energized, causing the first pre-charging relay K11 to disconnect. Power is then supplied to the inverter through the first main relay K21 to drive the motor body.

[0042] The three-phase AC power supply is rectified and filtered to obtain the bus voltage, which is 1.35 times the three-phase AC power supply voltage. The first reference voltage V1 is 1.2 times the three-phase AC power supply voltage.

[0043] According to some embodiments, such as Figure 2 As shown, the control unit 100 includes a first AND gate 1, a first NOT gate 2, and a control module. The first input terminal of the first AND gate 1 is connected to the frequency converter, the second input terminal of the first AND gate 1 is connected to the output terminal of the first NOT gate 2, the input terminal of the first NOT gate 2 is connected to the output terminal of the control module, the input terminal of the control module is connected to the frequency converter, the output terminal of the control module is connected to the control terminal of the second main relay K22, and the output terminal of the first AND gate 1 is connected to the control terminal of the second pre-charge relay K12.

[0044] The working principle of the above embodiment is as follows: when power needs to be supplied to the control terminal (coil terminal) of the second pre-charge relay K12, the inverter outputs a high level, and the control module outputs a low level. The high level output by the inverter supplies the first input terminal of the first AND gate 1. The low level output by the control module is converted to a high level after passing through the first NOT gate 2 and input to the second input terminal of the first AND gate 1. The first AND gate 1 outputs a high level to the control terminal (coil terminal) of the second pre-charge relay K12, and the second pre-charge relay K12 is energized. At this time, the low level output by the control module is input to the control terminal (coil terminal) of the second main relay K22, and the control terminal (coil terminal) of the second main relay K22 is not energized, so the second main relay K22 is in the open state.

[0045] When power is needed to the control terminal (coil terminal) of the second main relay K22, the inverter outputs a high level, the control module outputs a high level, and the high level output from the control module is input to the control terminal (coil terminal) of the second main relay K22, energizing and engaging the control terminal (coil terminal) of the second main relay K22. At this time, the high level output from the inverter supplies the first input terminal of the first AND gate 1, and the high level output from the control module is converted to a low level after passing through the first NOT gate 2 and input to the second input terminal of the first AND gate 1. The first AND gate 1 outputs a low level to the control terminal (coil terminal) of the second pre-charge relay K12, de-energizing and disconnecting the second pre-charge relay K12.

[0046] According to some embodiments, such as Figure 2 As shown, the control module includes a second AND gate 3 and a first comparator 5. The first input terminal of the first comparator 5 is connected to the charging voltage of the detected load, and the second input terminal of the first comparator 5 is connected to a first reference voltage V1. The first input terminal of the second AND gate 3 is connected to the frequency converter, and the second input terminal of the second AND gate 3 is connected to the first output terminal of the first comparator 5. The output terminal of the second AND gate 3 is connected to the control terminal of the second main relay K22, and the output terminal of the second AND gate 3 is connected to the second input terminal of the first AND gate 1 through the first NOT gate 2.

[0047] The working principle of the above embodiment is as follows: When power needs to be supplied to the control terminal (coil terminal) of the second pre-charge relay K12, the inverter outputs a high level. When the first comparator 5 detects that the charging voltage of the inverter is lower than the first reference voltage V1, the first output terminal of the first comparator 5 outputs a low level, and the second input terminal of the second AND gate 3 receives a low level, so the second AND gate 3 outputs a low level. Both the first and second input terminals of the first AND gate 1 receive a high level, so the first AND gate 1 outputs a high level to the control terminal (coil terminal) of the second pre-charge relay K12, and the second pre-charge relay K12 is energized. At this time, the low level output by the second AND gate 3 is input to the control terminal (coil terminal) of the second main relay K22, and the control terminal (coil terminal) of the second main relay K22 is not energized, so the second main relay K22 is in the open state.

[0048] When power needs to be supplied to the control terminal (coil terminal) of the second main relay K22, the inverter outputs a high level. After the first comparator 5 detects that the inverter's charging voltage is higher than the first reference voltage V1, the first output terminal of the first comparator 5 outputs a high level. The inverter outputs a high level to the first input terminal of the second AND gate 3, and the first output terminal of the first comparator 5 outputs a high level to the second input terminal of the second AND gate 3. Therefore, the second AND gate 3 outputs a high level. The high level output by the second AND gate 3 is input to the control terminal (coil terminal) of the second main relay K22, and the control terminal (coil terminal) of the second main relay K22 is energized and engaged. At this time, the first input terminal of the first AND gate 1 receives a high level. The high level output by the second AND gate 3 is converted to a low level after passing through the first NOT gate 2 and then input to the second input terminal of the first AND gate 1. Therefore, the first AND gate 1 outputs a low level to the control terminal (coil terminal) of the second pre-charge relay K12, and the second pre-charge relay K12 is de-energized and disconnected.

[0049] According to some embodiments, the control unit 100 further includes a shutdown delay circuit 6, the first input terminal of the first AND gate 1 is connected to the frequency converter through the shutdown delay circuit 6, and the first input terminal of the second AND gate 3 is connected to the frequency converter through the shutdown delay circuit 6.

[0050] The working principle based on the above embodiment is that the shutdown delay circuit 6 is used for motor demagnetization protection, that is, the shutdown delay ensures that the motor is completely demagnetized after the closing command is removed.

[0051] According to some embodiments, the control unit 100 further includes a pulse hold circuit 7, the first input terminal of the first AND gate 1 is connected to the output terminal of the shutdown delay circuit 6 and the first input terminal of the second AND gate 3 through the pulse hold circuit 7, and the input terminal of the shutdown delay circuit 6 is connected to the frequency converter.

[0052] The working principle of the above embodiment is that the pulse holding circuit 7 is used to protect the first resistor R1 and the second resistor R2. That is, when the closing command arrives, the maximum pre-charging time is 3 seconds to prevent the first resistor R1 and the second resistor R2 from overheating and burning out due to continuous closing of the pre-charging circuit under abnormal conditions.

[0053] According to some embodiments, the control unit 100 further includes a first turn-on delay circuit 8, and the output of the second AND gate 3 is connected to the first NOT gate 2 through the first turn-on delay circuit 8.

[0054] The working principle of the above embodiment is as follows: the first turn-on delay circuit 8 is used to control the first main relay K21 to lock itself when the second main relay K22 is energized. That is, the second pre-charge relay K12 and the first pre-charge relay K11 are turned off only after the first main relay K21 is fully closed. This also prevents DC voltage drop and current arcing caused by excessively long turn-off time of the pre-charge contactor coil during the switching of the two sets of relays.

[0055] According to some embodiments, the control module further includes a second turn-on delay circuit 9, and the second input terminal of the second AND gate 3 is connected to the first output terminal of the first comparator 5 through the second turn-on delay circuit 9.

[0056] The working principle based on the above embodiment is as follows: the second turn-on delay circuit 9 is used to ensure that the voltage is stable when the first main relay K21 is fully closed, that is, the inverter charging voltage is detected to be greater than the first reference voltage V1 and the output is delayed to ensure that the inverter charging voltage is stable above the first reference voltage V1, so as to prevent the detected inverter charging voltage fluctuation from causing the output of the first comparator 5 to be unstable, thereby causing the relay contactor to frequently turn on and off.

[0057] According to some embodiments, the control module further includes a second comparator 10 and a second NOT gate 4. The first input terminal of the second comparator 10 is connected to the voltage of the detection busbar, the second input terminal of the second comparator 10 is connected to the second reference voltage V2, and the second output terminal of the second comparator 10 is connected to the third input terminal of the second AND gate 3 through the second NOT gate 4.

[0058] The working principle of the above embodiment is as follows: when the second comparator 10 detects that the bus voltage is lower than the second reference voltage V2, the second output terminal of the second comparator 10 outputs a high level, which is converted to a low level by the second NOT gate 4 and then output to the third input terminal of the second AND gate 3. Therefore, the second AND gate 3 outputs a low level. At this time, the second pre-charge relay K12 can be energized and engaged or de-energized and disengaged according to the control of the frequency converter, while the second main relay K22 cannot be energized and disengaged.

[0059] When the second comparator 10 detects that the bus voltage is higher than the second reference voltage V2, the second output of the second comparator 10 outputs a low level. This low level is then converted to a high level by the second NOT gate 4 and output to the third input of the second AND gate 3. At this time, the second AND gate 3 is controlled according to the level signals of the first and second inputs. When both the first and second inputs of the second AND gate 3 are high, the second AND gate 3 outputs a high level, the second main relay K22 is energized and engaged, and the second pre-charge relay K12 is not energized and disengaged.

[0060] The three-phase AC power supply is rectified and filtered to obtain the bus voltage, which is 1.35 times the three-phase AC power supply voltage. The second reference voltage V2 is 1.3 times the three-phase AC power supply voltage.

[0061] The second comparator 10 and the second NOT gate 4 are used for inverter undervoltage protection. That is, when the rectifier loses power (due to fault or abnormality), the first main relay K21 and the second main relay K22 are disconnected. The first pre-charge relay K11 and the second pre-charge relay K12 can be engaged or disengaged according to the original control of the frequency converter, to prevent the fast fuse from burning out when the main circuit is engaged at the moment the rectifier recovers.

[0062] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0063] Although this disclosure has been described with reference to several typical embodiments, it should be understood that the terminology used is descriptive and exemplary, and not restrictive. Because this disclosure can be embodied in many forms without departing from the spirit or substance of this application, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A control circuit for hot-swappable busbars, characterized in that, The control circuit includes: A first pre-charge switch, a first main switch, a first resistor, and a second resistor are provided. The first input terminal of the first pre-charge switch is connected to the first input terminal of the first main switch, and the second input terminal of the first pre-charge switch is connected to the second input terminal of the first main switch. The first output terminal of the first pre-charge switch is connected to the first output terminal of the first main switch and the first electrode of the load through the first resistor, and the second output terminal of the first pre-charge switch is connected to the second output terminal of the first main switch and the second electrode of the load through the second resistor. The fuse switch has its first input terminal of the first pre-charge switch and the first input terminal of the first main switch connected to its first output terminal, its second input terminal of the first pre-charge switch and the second input terminal of the first main switch connected to its second output terminal, and its input terminal connected to the busbar. When the fuse switch is closed, both the first pre-charge switch and the first main switch are in the open state. When it is necessary to provide power to the load, the first pre-charge switch is closed to pre-charge the load. When the pre-charge reaches the set time, the first main switch is closed and the first pre-charge switch is opened, and the load is driven to work through the first main switch. The first pre-charge switch uses a first pre-charge relay. One end of the first controlled terminal of the first pre-charge relay is connected to the first input terminal of the first main switch. One end of the second controlled terminal of the first pre-charge relay is connected to the second input terminal of the first main switch. The other end of the first controlled terminal of the first pre-charge relay is connected to the first output terminal of the first main switch and the first electrode of the load through the first resistor. The other end of the second controlled terminal of the first pre-charge relay is connected to the second output terminal of the first main switch and the second electrode of the load through the second resistor. The control circuit also includes a second pre-charge relay and a control unit. The control unit is connected to both ends of the control terminal of the second pre-charge relay. One end of the controlled terminal of the second pre-charge relay is connected to one end of the power supply, and the other end of the controlled terminal of the second pre-charge relay is connected to the other end of the power supply through the control terminal of the first pre-charge relay. The first main switch adopts a first main relay. One end of the first controlled terminal of the first pre-charge relay is connected to one end of the first controlled terminal of the first main relay. One end of the second controlled terminal of the first pre-charge relay is connected to one end of the second controlled terminal of the first main relay. The other end of the first controlled terminal of the first pre-charge relay is connected to the other end of the first controlled terminal of the first main relay and the first electrode of the load through the first resistor. The other end of the second controlled terminal of the first pre-charge relay is connected to the other end of the second controlled terminal of the first main relay and the second electrode of the load through the second resistor. The control circuit further includes a second main relay. The control unit is connected to both ends of the control terminal of the second main relay. One end of the controlled terminal of the second main relay is connected to one end of the power supply. The other end of the controlled terminal of the second main relay is connected to one end of the third controlled terminal of the first pre-charge relay and one end of the third controlled terminal of the first main relay. The other end of the third controlled terminal of the first pre-charge relay and the other end of the third controlled terminal of the first main relay are both connected to one end of the control terminal of the first main relay. The other end of the control terminal of the first main relay is connected to the other end of the power supply. The control unit includes a first AND gate, a first NOT gate, and a control module. The first input terminal of the first AND gate is connected to the frequency converter, the second input terminal of the first AND gate is connected to the output terminal of the first NOT gate, the input terminal of the first NOT gate is connected to the output terminal of the control module, the input terminal of the control module is connected to the frequency converter, the output terminal of the control module is connected to the control terminal of the second main relay, and the output terminal of the first AND gate is connected to the control terminal of the second pre-charge relay. The control module includes a second AND gate and a first comparator. The first input of the first comparator is connected to the charging voltage of the detected load. The second input of the first comparator is connected to a first reference voltage. The first input of the second AND gate is connected to a frequency converter. The second input of the second AND gate is connected to the first output of the first comparator. The output of the second AND gate is connected to the control terminal of the second main relay. The output of the second AND gate is connected to the second input of the first AND gate through the first NOT gate.

2. The control circuit according to claim 1, characterized in that, The control unit further includes a shutdown delay circuit, wherein the first input terminal of the first AND gate is connected to the frequency converter through the shutdown delay circuit, and the first input terminal of the second AND gate is connected to the frequency converter through the shutdown delay circuit.

3. The control circuit according to claim 2, characterized in that, The control unit further includes a pulse hold circuit, wherein the first input terminal of the first AND gate is connected to the output terminal of the shutdown delay circuit and the first input terminal of the second AND gate through the pulse hold circuit, and the input terminal of the shutdown delay circuit is connected to the frequency converter.

4. The control circuit according to claim 1, characterized in that, The control unit further includes a first turn-on delay circuit, and the output of the second AND gate is connected to the first NOT gate through the first turn-on delay circuit.

5. The control circuit according to claim 1, characterized in that, The control module further includes a second turn-on delay circuit, and the second input terminal of the second AND gate is connected to the first output terminal of the first comparator through the second turn-on delay circuit.

6. The control circuit according to claim 1, characterized in that, The control module further includes a second comparator and a second NOT gate. The first input terminal of the second comparator is connected to the voltage of the detection busbar, the second input terminal of the second comparator is connected to a second reference voltage, and the second output terminal of the second comparator is connected to the third input terminal of the second AND gate through the second NOT gate.

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