Safe and reliable double-coil contactor control circuit

Abstract

A safe and reliable double-coil contactor control circuit comprises a power supply input end; the starting loop is provided with a starting coil; the holding loop is arranged in parallel with the starting loop and is provided with a holding coil; the auxiliary switch is arranged at the front end of the starting loop, is disconnected when the contactor is attracted, and cuts off the starting loop; and the control assembly is connected in the starting loop in series, the control end of the control assembly is connected with the rear end of the holding loop, and on-off of the starting loop is controlled according to a state signal of the holding loop. Coil dual power supply switching power supply is adopted, a starting coil adopts high-voltage excitation during starting, and low-voltage power supply is adopted in the maintaining process. A signal is provided to the control assembly at the tail end of the holding circuit to control the starting coil, when any element of a holding loop breaks down, excitation high voltage cannot work, fatal faults of a conventional energy-saving circuit are avoided, the problem of unreliable holding caused by catastrophic hazards brought to an electric appliance can be effectively avoided, and primary energy saving is achieved while reliable holding is guaranteed.

Description

Technical Field

[0001] This utility model relates to the field of contactors, specifically to a safe and reliable dual-coil contactor control circuit. Background Technology

[0002] As is well known, in electrical engineering, a contactor is an automated switch used to connect or disconnect AC or DC main circuits or high-capacity control circuits of loads. Its main control object is the electric motor, but it can also be used for other electrical loads such as electric heaters, welding machines, and lighting equipment. Contactors can not only connect and disconnect circuits, but also have low-voltage release protection. Furthermore, contactors have a large control capacity and are suitable for frequent operation and remote control, making them one of the important components in automatic control systems.

[0003] As energy-saving requirements for contactors gradually increase, the new national standard GB21518-2008 specifies the energy efficiency levels, energy efficiency limits, energy-saving evaluation values, and test methods for AC contactors. It divides the energy efficiency levels of contactors into three levels: Level 1, Level 2, and Level 3, measured by holding power VA. A VA level of 3 indicates a contactor meeting the entry-level standard, while Levels 2 and 1 are energy-saving products. This has played a positive role in promoting the research and application of energy-saving and noise-free technologies for AC contactors.

[0004] For example, Chinese patent CN222260905U discloses an AC contactor that specifically utilizes parallel or series connections between multiple coils to achieve contactor engagement and maintenance, thereby meeting energy efficiency requirements. However, the circuitry used poses significant risks in practical use. If any coil or diode in the holding circuit malfunctions, it will prevent the contactor from maintaining its engaged state, leading to a continuous engagement-disengagement-engagement cycle. Frequent engagement and disengagement will cause the connected electrical loads to frequently stop and start, resulting in equipment damage and potentially causing major production accidents. Utility Model Content

[0005] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide a safe and reliable dual-coil contactor control circuit.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A safe and reliable dual-coil contactor control circuit includes:

[0008] Power input terminal;

[0009] The starting circuit is equipped with a starting coil L1, which is used to provide the force for the contactor to engage;

[0010] The holding circuit is set in parallel with the starting circuit, and is equipped with a holding coil L2, which is used to provide a force to maintain the holding after the contactor is engaged;

[0011] The auxiliary switch SW1 is located at the front end of the starting circuit and is disconnected when the contactor is engaged, thus cutting off the starting circuit.

[0012] A control component, which is connected in series in the start-up circuit, has its control terminal connected to the rear end of the holding circuit, and controls the on / off state of the start-up circuit 200 according to the status signal of the holding circuit.

[0013] The auxiliary switch SW1 is a normally closed switch.

[0014] The control component includes a silicon controlled rectifier (SCR) Q1, the control terminal of which is connected to the rear end of the holding circuit.

[0015] An isolation circuit is provided between the rear end of the holding circuit and the control component.

[0016] The isolation circuit is an optocoupler isolation circuit.

[0017] The holding circuit includes a power conversion circuit connected to the power input terminal and a holding coil L2 connected to the output terminal of the power conversion circuit.

[0018] The power conversion circuit includes a rectifier bridge and current-limiting capacitors connected in series with the two input terminals of the rectifier bridge.

[0019] The power conversion circuit includes a rectifier bridge and current-limiting resistors connected in series with the two input terminals of the rectifier bridge.

[0020] The auxiliary switch SW1 can be one or two.

[0021] The beneficial effects of this invention are as follows: It employs a dual-power supply switching system for the coil. During startup, coil L1 is energized with high voltage, while during the holding process, it switches to low voltage power. Simultaneously, a signal is provided to the control component at the end of the holding circuit's current loop to control the start coil L1. If any component in the holding circuit fails, the high-voltage energizer cannot operate, avoiding the fatal malfunctions of conventional energy-saving circuits and the vicious cycle of pull-in and release. This effectively prevents unreliable holding problems caused by catastrophic damage to electrical appliances, achieving first-level energy saving while ensuring reliable holding. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the principle of this utility model.

[0023] Figure 2 This is a circuit diagram of Embodiment 1 of the present invention.

[0024] Figure 3 This is a circuit diagram of Embodiment 2 of the present invention.

[0025] Figure 4 This is a circuit diagram of Embodiment 3 of the present invention. Detailed Implementation

[0026] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0027] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0028] like Figure 1 As shown, this utility model discloses a safe and reliable dual-coil contactor control circuit, which includes:

[0029] The power input terminal 100 has at least two inputs for DC or AC power input;

[0030] The starting circuit 200 is equipped with a starting coil L1, which is used to provide the contactor with the force to engage;

[0031] The holding circuit 300 is connected in parallel with the starting circuit 200 and is equipped with a holding coil L2, which is used to provide a force to maintain the holding after the contactor is engaged.

[0032] The auxiliary switch SW1 is located at the front end of the starting circuit 200. It is disconnected when the contactor is engaged, thus cutting off the starting circuit 200.

[0033] The control component 400 is connected in series in the start-up circuit 200, and its control terminal is connected to the rear end of the holding circuit 300. It controls the on / off state of the start-up circuit 200 according to the status signal of the holding circuit 300.

[0034] Its specific working principle is as follows:

[0035] When the contactor starts, the auxiliary switch is closed. The starting circuit and the holding circuit are connected in parallel. The holding circuit is in a normal conducting state, which provides a signal to the control component to conduct. Therefore, the starting circuit 200 is conducting. That is, when the starting coil L1 is energized, it drives the moving iron core of the contactor to move relative to the stationary iron core. When the contactor is engaged, the moving iron core is used to disconnect the auxiliary switch. At this time, the starting circuit is disconnected, and the holding circuit supplies power to the holding coil through a small current, thereby maintaining the contactor's engaged state and achieving energy saving. When the holding circuit malfunctions, it cannot output a signal to enable the control component to conduct, thereby cutting off the starting circuit. Even if the entire contactor is disconnected, frequent engagement-disengagement-engagement actions will not occur.

[0036] Example 1

[0037] like Figure 2 As shown, the power input terminal has two input terminals, AC1 and AC2, which are connected to the input terminal of rectifier bridge D1. The rectifier bridge achieves step-down output. At the same time, the positive output terminal of rectifier bridge D1 is divided into two paths. One path is connected to the auxiliary switch SW1, the start-up coil L1, and the thyristor Q1 in sequence, and is connected to the negative output terminal of rectifier bridge to form a start-up circuit. The auxiliary switch SW1 and the control element (thyristor Q1) are connected in series in this start-up circuit. The other path of the positive output terminal of rectifier bridge D1 is connected to the negative output terminal of rectifier bridge D1 in sequence through the holding coil L2 and the resistor R6 to form a holding circuit. The holding circuit and the start-up circuit are set in parallel. The rear end of the holding coil L2 is connected to the control terminal of thyristor Q1 through the voltage divider resistors R7 and R8. The thyristor Q1 is controlled by the change of the voltage at the rear end of the holding coil L2. At the same time, a freewheeling diode DL is connected in parallel across the two ends of the holding coil L2.

[0038] When the contactor is working normally, the auxiliary switch SW1 is closed. When the holding circuit is working normally, the thyristor Q1 is turned on, so that the starting circuit forms a conducting loop. Then, the starting coil L1 receives a high voltage and the moving contact of the contactor is attracted. When the moving contact is attracted, the auxiliary switch SW1 is turned off. At this time, the starting coil L1 is no longer energized. Then, the holding coil L2 is used to maintain the attracted state. At the same time, this embodiment relies on the normal operation of the holding circuit to enable the starting circuit to work normally. Therefore, when the holding circuit fails, the contactor will be directly disconnected and there will be no repeated action of attracting-disconnecting-attracting.

[0039] Meanwhile, Example 1 can be applied to contactors with voltages below 48V.

[0040] Example 2

[0041] Example 2 can be applied to contactors with voltages of 110-220V.

[0042] like Figure 3As shown, its power input includes two input terminals AC1 and AC2, with a varistor R1 connected in parallel between the two input terminals for protection. The holding circuit includes a power conversion circuit and a holding coil L2. The power conversion circuit includes a rectifier bridge D1, whose two output terminals are connected in series with current-limiting resistors R2, R3 and R4, R6 respectively, and connected to input terminals AC1 and AC2. The duty cycle of the voltage of the holding coil L2 is controlled in real time by using resistor current limiting, so that the current of the holding coil is kept at a constant value. A freewheeling diode DL is connected in parallel across the two ends of the holding coil. At the same time, the positive output terminal of the rectifier bridge D1 is connected to the negative output terminal in sequence through the holding coil L2 and resistor R6, forming a complete circuit. An electrolytic capacitor C2 is connected in parallel across the two output terminals of the rectifier bridge D1 for filtering.

[0043] The starting circuit includes a rectifier bridge D3 for polarity switching. Its input terminals are connected to input terminals AC1 and AC2 via one or two auxiliary switches. In this embodiment, two auxiliary switches are used, connected in series in the two input branches of the rectifier bridge D3. The positive output terminal of the rectifier bridge D3 is connected to its negative output terminal via the starting coil L1 and the thyristor Q1. The thyristor Q1 serves as a control element, and its control terminal is connected to the rear end of the holding coil L2 via an isolation circuit. This isolation circuit includes an optocoupler U1. Pin 1 of the optocoupler U1 is connected to the rear end of the holding coil L2 via a resistor R7, while pin 2 of the optocoupler U1 is connected to the negative output terminal of the rectifier bridge D1. Therefore, when the holding circuit is in normal operation, the optocoupler… When the LED is working normally, but the holding circuit malfunctions, the optocoupler will not work. At the same time, the optocoupler can also achieve strong and weak current isolation. Pin 3 of the optocoupler U1 is connected to the control terminal of the thyristor. Pin 3 is also connected to the negative output terminal of the rectifier bridge D3 through resistor R8. Pin 4 of the optocoupler U1 is connected to the front end of the start-up coil through resistors R9 and R10 and diode D2. The connection nodes of resistors R9 and R10 are connected to the negative output terminal of the rectifier bridge D3 through resistor R11 and capacitor C1, respectively. That is, the thyristor is controlled by diode D2, resistors R9, R10 and R11. When the optocoupler is working, it can drive the thyristor to conduct, so that the start-up circuit is in a conducting state. When the holding circuit is normal, the starting circuit uses a strong voltage to drive the starting coil L1 to engage the contactor, and uses the force generated by the contactor to disconnect the auxiliary switch. At this time, even if the optocoupler is conducting, the starting circuit is in an open state. However, when the holding circuit fails and the contactor is disconnected, the optocoupler does not work, so the starting circuit is still in an open state when the auxiliary switch is closed, and therefore cannot engage again.

[0044] Example 3

[0045] Example 3 can be used for contactors of 230-660V.

[0046] like Figure 4 As shown, its power input includes two input terminals AC1 and AC2, with a varistor R1 connected in parallel between them for protection. The holding circuit includes a power conversion circuit and a holding coil L2. The power conversion circuit includes a rectifier bridge D1, whose two output terminals are connected to input terminals AC1 and AC2 respectively through current-limiting capacitors C3 and C4. The duty cycle of the voltage of the holding coil L2 is controlled in real time by using capacitor current limiting to keep the current of the holding coil at a constant value. A freewheeling diode DL is connected in parallel across the two ends of the holding coil. The freewheeling diode mainly releases the high voltage at the tail end of the holding coil when the power is off, preventing it from impacting R7 and U1, thus providing protection. At the same time, the positive output terminal of the rectifier bridge D1 is connected to the negative output terminal in sequence through the holding coil L2 and resistor R6 to form a complete circuit. An electrolytic capacitor C2 is connected in parallel across the two output terminals of the rectifier bridge D1 for filtering.

[0047] In this embodiment, two auxiliary switches are used, connected in series with the two input terminals AC1 and AC2 respectively. Auxiliary switch SW1 is connected to the front end of the start coil L1, and auxiliary switch SW2 is connected to the cathode of the thyristor. The rear end of the start coil L1 is connected to the anode of the thyristor Q1. The thyristor Q1 serves as a control element, and its control terminal is connected to the rear end of the holding coil L2 via an isolation circuit. This isolation circuit includes an optocoupler U1. Pin 1 of the optocoupler U1 is connected to the rear end of the holding coil L2 via a resistor R7, and pin 2 of the optocoupler U1 is connected to the negative output terminal of the rectifier bridge D1. Thus, when the holding circuit is in normal operation, the LED of the optocoupler operates normally, and the holding circuit... If a circuit fault occurs, the optocoupler will not work. At the same time, the optocoupler can also achieve strong and weak current isolation. Pin 3 of the optocoupler U1 is connected to the control terminal of the thyristor. Pin 3 is also connected to the cathode of the thyristor Q1 through resistor R8. Pin 4 of the optocoupler U1 is connected to the front end of the start-up coil through resistors R9 and R10 and diode D2. The connection nodes of resistors R9 and R10 are connected to the negative output terminal of rectifier bridge D3 through resistor R11 and capacitor C1, respectively. That is, the thyristor is controlled by diode D2, resistors R9, R10 and R11. When the optocoupler is working, it can drive the thyristor to conduct, so that the start-up circuit is in a conducting state. When the holding circuit is normal, the starting circuit uses a strong voltage to drive the starting coil L1 to engage the contactor, and uses the force generated by the contactor to disconnect the auxiliary switch. At this time, even if the optocoupler is conducting, the starting circuit is in an open state. However, when the holding circuit fails and the contactor is disconnected, the optocoupler does not work, so the starting circuit is still in an open state when the auxiliary switch is closed, and therefore cannot engage again.

[0048] In the above embodiments, the control element is a thyristor, while in other embodiments, a switching circuit such as a MOSFET or a transistor can also be used. It can realize the conduction or disconnection of the start-up circuit under the signal control of the holding circuit. In some embodiments, a microcontroller can also be used for control.

[0049] The embodiments should not be regarded as limitations on the present invention, but any improvements made based on the spirit of the present invention should be within the protection scope of the present invention.

Claims

1. A safe and reliable dual-coil contactor control circuit, characterized in that: It includes: Power input terminal (100); The starting circuit (200) is equipped with a starting coil L1, which is used to apply force to the contactor to engage; The holding circuit (300) is connected in parallel with the starting circuit (200) and is provided with a holding coil L2, which is used to provide a force to maintain the holding after the contactor is engaged; The auxiliary switch SW1 is located at the front end of the starting circuit (200), and is disconnected when the contactor is engaged, thus cutting off the starting circuit (200). A control component (400) is connected in series in the start-up circuit (200), and its control end is connected to the rear end of the holding circuit (300). It controls the on / off state of the start-up circuit (200) according to the status signal of the holding circuit (300).

2. The safe and reliable dual-coil contactor control circuit according to claim 1, characterized in that: The auxiliary switch SW1 is a normally closed switch.

3. A safe and reliable dual-coil contactor control circuit according to claim 1 or 2, characterized in that: The control component (400) includes a silicon controlled rectifier (SCR) Q1, the control terminal of which is connected to the rear end of the holding circuit (300).

4. The safe and reliable dual-coil contactor control circuit according to claim 3, characterized in that: An isolation circuit is provided between the rear end of the holding circuit (300) and the control component (400).

5. A safe and reliable dual-coil contactor control circuit according to claim 4, characterized in that: The isolation circuit is an optocoupler isolation circuit.

6. The safe and reliable dual-coil contactor control circuit according to claim 1, characterized in that: The holding circuit (300) includes a power conversion circuit connected to the power input terminal (100) and a holding coil L2 connected to the output terminal of the power conversion circuit.

7. A safe and reliable dual-coil contactor control circuit according to claim 6, characterized in that: The power conversion circuit includes a rectifier bridge and current-limiting capacitors connected in series with the two input terminals of the rectifier bridge.

8. A safe and reliable dual-coil contactor control circuit according to claim 6, characterized in that: The power conversion circuit includes a rectifier bridge and current-limiting resistors connected in series with the two input terminals of the rectifier bridge.

9. A safe and reliable dual-coil contactor control circuit according to claim 1, characterized in that: The auxiliary switch SW1 can be one or two.

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