Four-gear interlocking type inverter pre-charging switch and control method

Abstract

The invention discloses a four-gear interlocking type inverter pre-charging switch and a control method, and relates to the technical field of inverters, the switch comprises an operating handle capable of switching at four angle positions, four groups of contacts, a pre-charging loop, a main loop, a direct current detection circuit and a main loop locking mechanism; the pre-charging loop is formed by connecting a first contact group, a second contact group and a current-limiting resistor in series; the main loop comprises a third contact group and a fourth contact group; the main loop locking mechanism is an electromagnetic lock and is used for locking or unlocking the operating handle according to a voltage detection result; according to the control method, the standby stage, the pre-charging stage, the unlocking judgment stage, the transition stage and the main loop operation stage are sequentially achieved through handle gear switching. Through the combination of mechanical interlocking and voltage detection, the pre-charging process is forcibly standardized, the surge current is suppressed, and the starting safety and reliability of the inverter are improved.

Description

Technical Field

[0001] This invention relates to the field of inverter technology, specifically to a four-position interlocking inverter pre-charge switch and control method. Background Art

[0002] During the inverter startup process, the initial voltage of its internal capacitor is zero. If the DC bus (such as 510VDC or 1000VDC) is directly connected to the main circuit, a huge charging current (approximately short-circuit current) will be generated instantly. This surge current may exceed the rated withstand value of the components, causing damage to the inverter power devices, bus cables or switch contacts, and in severe cases, causing safety accidents such as circuit fires.

[0003] Existing inverter pre-charging schemes have the following specific drawbacks:

[0004] Insufficient surge suppression: Some solutions use a single-position switch to directly connect the main circuit, relying entirely on the inverter's internal software protection. If the software response is delayed or fails, it cannot physically block the surge current.

[0005] The operation process is not subject to mandatory constraints: Traditional dual-position switches ("disconnect-connect") lack the interlocking mechanism between pre-charging and the main circuit. Operators may mistakenly skip the pre-charging step and directly connect the main circuit, leading to surge risk.

[0006] Voltage detection and locking are disconnected: In the existing solution, the pre-charge voltage lacks automatic detection and mechanical locking linkage. If the operator misjudges the voltage status and forcibly switches the switch, the main circuit will still be connected when the pre-charge is insufficient.

[0007] The aforementioned problems result in low safety, poor operational fault tolerance, and rapid component wear of existing inverter pre-charge systems, making it difficult to meet the requirements of industrial-grade inverters for startup reliability and lifespan. Summary of the Invention

[0008] The mechanical locking mechanism, with its four-position handle and voltage interlock, forces the "pre-charging to voltage detection to main circuit connection" process, thus solving the problems of surge suppression and preventing misoperation.

[0009] A four-position interlocked inverter precharge switch includes:

[0010] The operating handle can be switched between four positions with an angle of -45°, -15°, +15°, and +45° to the horizontal.

[0011] Four groups of contacts: Group 1, Group 2, Group 3, and Group 4;

[0012] The pre-charge circuit, used for pre-charge protection, consists of a first contact group, a current-limiting resistor, and a second contact group connected in series.

[0013] The main circuit, used to power the inverter, includes a third contact group and a fourth contact group connected in series.

[0014] A DC detection circuit is connected between the pre-charge circuit and the inverter to monitor the inverter bus voltage.

[0015] Main circuit locking mechanism: powered by 24VDC power supply and electrically connected to DC detection circuit, used to lock the operating handle when the inverter bus voltage does not reach the preset threshold, preventing it from switching from -15° to +15° position; and to release the lock on the operating handle when the inverter bus voltage reaches the preset threshold.

[0016] As a preferred embodiment of the present invention, the contact on / off relationship of the operating handle in different positions is as follows:

[0017] -45°: The first, second, third, and fourth contact groups are all disconnected;

[0018] -15°: The first and second contact groups are connected, and the third and fourth contact groups are disconnected;

[0019] +15°: All four contact groups are closed;

[0020] +45°: The first and second contact groups are open, and the third and fourth contact groups are closed.

[0021] As a preferred embodiment of the present invention, the current-limiting resistor is composed of two resistors with a rated resistance of 80Ω and a rated power of 200W connected in series.

[0022] As a preferred embodiment of the present invention, the instantaneous overload power of the current limiting resistor is ≥3kW / s, its maximum instantaneous current is 5A, and its rated voltage is 1000VDC.

[0023] As a preferred embodiment of the present invention, the main circuit locking mechanism is an electromagnetic lock powered by 24VDC.

[0024] As a preferred embodiment of the present invention, the preset threshold of the main circuit locking mechanism is ≥500V to adapt to 510-600V DC bus.

[0025] As a preferred embodiment of the present invention, the rated capacity of the first and second contact groups is 10A 1000VDC, the rated current of the third and fourth contact groups is configured according to the rated current of the inverter, the rated voltage is DC1000V, and the overload capacity is not less than twice the rated current.

[0026] As a preferred embodiment of the present invention, the pre-charge circuit is connected in series with a fuse having a rated current of 10A and a rated voltage of 1000VDC.

[0027] The present invention also provides a control method for a four-position interlocked inverter pre-charge switch, comprising the following steps:

[0028] Closing operation:

[0029] Step 1: Standby stage: With the operating handle set to -45°, all contact groups are disconnected, and the inverter is electrically isolated from the DC bus;

[0030] Step 2: Pre-charging stage: When the operating handle is turned to -15°, the first and second contact groups are connected, and the DC bus charges the inverter capacitor through the current-limiting resistor. The DC detection circuit monitors the bus voltage in real time.

[0031] Step 3: Unlocking Judgment Stage: If the inverter bus voltage reaches the preset threshold, the main circuit locking mechanism unlocks; if it does not reach the threshold, the locking mechanism remains locked, preventing the handle from switching to +15°; the indicator light shows the status of the locking mechanism, turning off means locked; lighting up means unlocked.

[0032] Step 4: Transition Phase: After unlocking, turn the operating handle to +15°, the third and fourth contact groups are connected, and the pre-charging circuit and the main circuit are simultaneously connected;

[0033] Since the voltage on both sides of the third and fourth contact groups is consistent during operation, there is no problem of arcing during closing and opening, which reduces the requirement for breaking capacity and can significantly reduce the contact volume.

[0034] Step 5: Main circuit stage: Move the operating handle to +45°, the first and second contact groups are disconnected, and only the third and fourth contact groups remain conductive, so that the inverter can operate stably; the first and second contact groups are disconnected to avoid the charging resistor from overheating due to excessive contact resistance when the third and fourth contact groups are conductive.

[0035] Opening operation:

[0036] Once the inverter is confirmed to be in a stopped state, the operating handle is turned to -45°, all contact groups are open, and the inverter is electrically isolated from the DC bus. When the inverter is in a stopped state, the input and output potentials of the third and fourth contacts are the same, no current is generated, and the breaking capacity requirement is not high.

[0037] By adopting the above technical solution, the present invention has the following beneficial effects:

[0038] This invention, through the cooperation of a four-position operating handle and an interlocking mechanism, forces the implementation of the "pre-charging - voltage detection - main circuit connection" process, effectively avoiding surge current damage to components caused by misoperation and improving system safety;

[0039] The pre-charge circuit uses current-limiting resistors and fuses with specific parameters, which can not only complete charging quickly, but also provide effective protection in case of overload.

[0040] The main circuit locking mechanism automatically unlocks based on voltage detection, ensuring that the main circuit is only allowed to be connected after sufficient pre-charging. It has strong compatibility and reduces safety hazards caused by human operation.

[0041] The contact group has a capacity-graded design to meet the different current requirements of pre-charging and main power supply, thus extending the service life of the switch. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the overall circuit structure of the present invention;

[0043] Figure 2 This is a schematic diagram of the operating handle structure of the present invention;

[0044] Figure 3 This is a diagram showing the on / off state of the switch contacts of the present invention at different positions;

[0045] Figure 4 This is a graph showing the voltage-current variation of the current-limiting resistor over time during the pre-charging process of the present invention.

[0046] In the diagram: 1. First contact group; 2. Second contact group; 3. Third contact group; 4. Fourth contact group; 5. Current limiting resistor; 6. Fuse; 7. DC detection circuit; 8. Main circuit locking mechanism. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0048] This invention aims to fill the gap in manual pre-charge switches for integrated industrial inverters, avoiding problems such as poor surge current suppression, easy misoperation, low safety, large size, and insufficient adaptability. It provides a four-position interlocking inverter pre-charge switch and control method, which combines mechanical position interlocking with voltage detection to enforce and standardize the pre-charge process, thereby improving the safety and reliability of inverter startup.

[0049] Example 1

[0050] like Figures 1 to 4 As shown, a four-position interlocked inverter pre-charge switch includes: an operating handle that can be switched between four positions: -45°, -15°, +15°, and +45°, corresponding to different contact on / off states; and four sets of contacts: as shown in the image. Figure 4 The first contact group 1 (contacts 1-2), the second contact group 2 (contacts 3-4), the third contact group 3 (contacts 5-6), and the fourth contact group 4 (contacts 7-8) have the following contact on / off relationships when the operating handle is in different positions:

[0051] -45°: The first, second, third, and fourth contact groups are all disconnected;

[0052] -15°: The first and second contact groups are connected, and the third and fourth contact groups are disconnected;

[0053] +15°: All four contact groups are closed;

[0054] +45°: The first and second contact groups are open, and the third and fourth contact groups are closed;

[0055] The pre-charge circuit, used for pre-charge protection, consists of a first contact group 1, a current-limiting resistor 5, and a second contact group 2 connected in series, and a fuse 6 with a rated current of 10A and a rated voltage of 1000VDC is connected in series; the current-limiting resistor 5 consists of two resistors with a rated resistance of 80Ω, a rated power of 200W, and a rated voltage of 1000VDC connected in series, with an instantaneous overload power ≥3kW / s and a maximum instantaneous current of 5A;

[0056] Explanation of the use of current-limiting resistor 5: During charging, current-limiting resistor 5 is in an overload and heat-generating state. Due to the short duration, it is within the allowable limit range of the current-limiting resistor, but it needs to cool down for 2-3 minutes before the next operation. Here, the smaller the current-limiting resistor capacity, the greater the instantaneous overload capacity and the smaller its size. There are many resistors on the market with an overload capacity of 10 times the rated capacity for 5 seconds. However, in this solution, the instantaneous limit current does not exceed 1 second, and the overload capacity of the current-limiting resistor can be used at 20 times. Considering safety factors, this solution configures the current-limiting resistor at 15 times the 1 second. The above configuration can meet the current limiting requirements for a short time and reduce the size of the resistor, which is more in line with the miniaturization requirements of this solution.

[0057] The main circuit, used to power the inverter, includes a third contact group 3 and a fourth contact group 4 connected in series. In this embodiment, the main circuit is connected to a 510VDC bus.

[0058] The rated capacity of the first and second contact groups is 10A 1000VDC. The rated capacity of the third and fourth contact groups is configured according to the rated current of the inverter, the rated voltage is DC1000V, and the overload capacity is not less than twice the rated current.

[0059] DC detection circuit 7 is connected between the pre-charge circuit and the inverter to monitor the inverter bus voltage. DC detection circuit 7 can be a circuit composed of a voltage sensor, a signal conditioning circuit, and a comparator. The components are not limited here, and additional or fewer components can be added or removed to achieve the detection purpose. In this scheme, a Hall effect voltage sensor is used, with its input connected between the pre-charge circuit and the inverter to collect the inverter bus voltage signal. The signal conditioning circuit filters and amplifies the signal output from the voltage sensor to remove noise and adjust the signal to a suitable range for the comparator input. The comparator uses an LM393, with its non-inverting input connected to the conditioned voltage signal and its inverting input connected to a preset threshold voltage (corresponding to a 500V reference voltage). When the collected bus voltage signal is greater than or equal to the preset threshold, the comparator outputs a high level; otherwise, it outputs a low level, thus detecting whether the bus voltage meets the standard. Of course, the structure of DC detection circuit 7 is not limited to the above form, and other structures that can achieve the same function can also be used.

[0060] Main circuit locking mechanism 8: An electromagnetic lock powered by a 24VDC power supply, electrically connected to the DC detection circuit 7, is used to lock the operating handle when the inverter bus voltage does not reach a preset threshold (≥500V, compatible with 510VDC DC bus), preventing it from switching from -15° to +15°. Specifically, the main circuit locking mechanism 8 can be composed of an electromagnet, a locking tongue, a spring, and a housing. Other components that can achieve the same function can be added, removed, or replaced; there are no restrictions here. The electromagnet coil is connected to the output terminal of the comparator in the DC detection circuit. When the comparator outputs a low level (bus voltage not reaching the threshold), the electromagnet coil is not energized. Under the action of the spring, the latch extends out of the housing and embeds into the corresponding lock hole on the operating handle, preventing the operating handle from switching from -15° to +15°. When the comparator outputs a high level (bus voltage reaching the threshold), the electromagnet coil is energized, generating magnetic force that attracts the latch to retract into the housing against the spring force. The lock hole on the operating handle separates from the latch, and the handle can smoothly switch from the -15° to the +15° position. At the same time, the indicator light powered by the 24VDC power supply ( Figure 1 (shown in the middle) bright;

[0061] Indicator lights can indicate the status of the locking mechanism; the light indicates that the mechanism is unlocked. This involves equipment and personal safety. If necessary, a voltmeter can be installed on the inverter bus to allow operators to confirm the status and increase the reliability of the operating system. Of course, the structure of the main circuit locking mechanism is not limited to the above form; other structures that can achieve the same function can also be used.

[0062] A control method for a four-position interlocked inverter precharge switch includes the following steps:

[0063] Closing operation:

[0064] Step 1: Standby stage: With the operating handle set to -45°, all contact groups are disconnected, and the inverter is electrically isolated from the DC bus;

[0065] Step 2: Pre-charging stage: When the operating handle is turned to -15°, the first and second contact groups are connected, and the DC bus charges the inverter capacitor through the current-limiting resistor. The DC detection circuit monitors the bus voltage in real time.

[0066] Step 3: Unlock Judgment Stage: If the inverter bus voltage reaches the preset threshold, the main circuit locking mechanism will unlock and the indicator light will illuminate; if the threshold is not met, the indicator light will not illuminate, the locking mechanism will remain locked, and the handle will be prevented from switching to +15°.

[0067] Step 4: Transition Phase: After unlocking, the indicator light will illuminate. Move the operating handle to +15°, and the third and fourth contact groups will be connected. The pre-charging circuit and the main circuit will be connected simultaneously. Since the voltage on both sides of the third and fourth contact groups is consistent during operation, there is no problem of arcing during closing and opening. The requirements for breaking capacity are low, the contact volume can be greatly reduced, and the safety is high.

[0068] Step 5: Main circuit stage: Move the operating handle to +45°, the first and second contact groups are disconnected, and only the third and fourth contact groups remain connected, so that the inverter can operate stably; the first and second contact groups are disconnected to avoid the charging resistor from overheating due to excessive contact resistance when the third and fourth contact groups are connected.

[0069] Opening operation:

[0070] Confirm that the inverter is in the stopped state, turn the operating handle one step at a time to -45°, all contact groups are disconnected, and the inverter is electrically isolated from the DC bus;

[0071] When the inverter is in a stopped state, the input and output potentials of the third and fourth contacts are the same, and no current is generated, so the breaking capacity requirement is not high. This solution offers very high safety in both opening and closing operations and is suitable for most scenarios.

[0072] All components mentioned in this article are general standard parts or components known to those skilled in the art. Their structures and principles can be learned by those skilled in the art through technical manuals or conventional experimental methods, so they will not be described in detail here.

[0073] While the specific embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and modifications or variations without creative effort are still within the protection scope of the present invention.

Claims

1. A four-position interlocking inverter pre-charge switch, characterized in that, include: The operating handle can be switched between four positions with an angle of -45°, -15°, +15°, and +45° to the horizontal. Four groups of contacts: Group 1, Group 2, Group 3, and Group 4; The pre-charge circuit, used for pre-charge protection, consists of a first contact group, a current-limiting resistor, and a second contact group connected in series. The main circuit, used to power the inverter, includes a third contact group and a fourth contact group connected in series. A DC detection circuit is connected between the pre-charge circuit and the inverter to monitor the inverter bus voltage. Main circuit locking mechanism: powered by 24VDC power supply and electrically connected to DC detection circuit, used to lock the operating handle when the inverter bus voltage does not reach the preset threshold, preventing it from switching from -15° to +15° position; and to release the lock on the operating handle when the inverter bus voltage reaches the preset threshold.

2. The four-position interlocked inverter pre-charge switch according to claim 1, characterized in that: The contact on / off relationship of the operating handle in different positions is as follows: -45°: The first, second, third, and fourth contact groups are all disconnected; -15°: The first and second contact groups are connected, and the third and fourth contact groups are disconnected; +15°: All four contact groups are closed; +45°: The first and second contact groups are open, and the third and fourth contact groups are closed.

3. The four-position interlocked inverter pre-charge switch according to claim 1, characterized in that: The current-limiting resistor consists of two resistors with a rated resistance of 80Ω and a rated power of 200W connected in series.

4. A four-position interlocked inverter pre-charge switch according to claim 1, characterized in that: The instantaneous overload power of the current-limiting resistor is ≥3kW / s.

5. A four-position interlocked inverter pre-charge switch according to claim 1, characterized in that: The main circuit locking mechanism is an electromagnetic lock powered by 24VDC.

6. A four-position interlocked inverter pre-charge switch according to claim 1, characterized in that: The main circuit locking mechanism has a preset threshold of ≥500V and is compatible with 510V-600V DC bus.

7. A four-position interlocked inverter pre-charge switch according to claim 1, characterized in that: The rated capacity of the first and second contact groups is 10A 1000VDC; the rated current of the third and fourth contact groups is not less than the rated DC current of the inverter, the rated voltage is 1000VDC, and the third and fourth contact groups have an overload capacity of not less than twice the rated current.

8. A four-position interlocked inverter pre-charge switch according to claim 1, characterized in that: The pre-charge circuit is connected in series with a fuse rated at 10A and rated at 1000VDC.

9. The control method for the pre-charge switch of a four-position interlocked inverter according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Standby stage: With the operating handle set to -45°, all contact groups are disconnected, and the inverter is electrically isolated from the DC bus; Step 2: Pre-charging stage: When the operating handle is turned to -15°, the first and second contact groups are connected, and the DC bus charges the inverter capacitor through the current-limiting resistor. The DC detection circuit monitors the bus voltage in real time. Step 3: Unlocking Judgment Stage: If the inverter bus voltage reaches the preset threshold, the main circuit locking mechanism unlocks; if it does not reach the threshold, the locking mechanism remains locked, preventing the operating handle from switching to +15°. Step 4: Transition Phase: After unlocking, turn the operating handle to +15°, the third and fourth contact groups are connected, and the pre-charging circuit and the main circuit are simultaneously connected; Step 5: Main circuit stage: When the operating handle is turned to +45°, the first and second contact groups are disconnected, and only the third and fourth contact groups remain connected, allowing the inverter to operate stably.

10. The control method for the pre-charge switch of a four-position interlocked inverter according to claim 9, characterized in that, The control method also includes a tripping operation. The tripping operation involves confirming that the inverter is in a stopped state, and then turning the operating handle sequentially from +45° to -45° to disconnect all contact groups.

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