Overload and short circuit protection circuit in direct current starting control circuit of contactor

Abstract

The utility model discloses an overload and short circuit protection circuit in a contactor direct current starting control circuit, which comprises a rectifier bridge, a stabilized power supply, a starting circuit and a control circuit, two ends of the rectifier bridge are externally connected with a power supply, the other two ends of the rectifier bridge are respectively connected with a first capacitor, and the first capacitor is respectively connected with the starting circuit and the stabilized power supply. The starting circuit is connected with the control circuit and the AC contactor through relay contacts. One end of the voltage-stabilized power supply is connected with the AC contactor. The beneficial effects of the utility model are that the AC contactor is provided with the rectifier bridge, the voltage-stabilized power supply, the starting circuit and the control circuit, thereby achieving the functions of overload and short-circuit tripping of the AC contactor; when a main contact transmission loop of the alternating current contactor is overloaded and short-circuited, the voltage sent to the comparison input end of the voltage comparator by the mutual inductor rises and is higher than a preset threshold voltage value of the voltage comparator, the output end of the voltage comparator is changed into low voltage, the output end of the control circuit is switched off, and the alternating current contactor trips to realize line protection.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of artificial intelligence especially overload and short circuit protection circuit in contactor DC starting control circuit. BACKGROUND

[0002] Contactors are applied to power, power distribution and power consumption occasions, and are used in industrial electricity to generate a magnetic field by the current flowing through the coil, so that the contact is closed to achieve the control of the electric appliance of the load,

[0003] In electrotechnics, the contactor is a device that can quickly cut off the AC and DC main circuit and can frequently turn on and off the large current control circuit, so it is often used in electric motors as a control object, and can also be used as a control of factory equipment, electric heaters, working mother machines and various power loads. The contactor not only can turn on and off the circuit, but also has a low voltage release protection function; the contactor control capacity is large, suitable for frequent operation and remote control, and is one of the important elements in the automatic control system;

[0004] In industrial electricity, there are many types of contactors, and the working current is between 5A and 1000A, which is quite widely used. In the use process, the voltage at both ends of the AC contactor coil is from large to small, and the current is from high to low. Because the starting circuit current is from large to small, the existing circuit cannot ensure that the starting circuit is turned off in a small current state, which causes the reverse high voltage generated when the high voltage and large current are broken to cause the arc damage of the breaking switch contact point

[0005] Therefore, it is necessary to provide an overload and short circuit protection circuit in a contactor DC starting control circuit for the above problems. INVENTION CONTENTS

[0006] In view of the deficiencies in the prior art, the purpose of the utility model is to provide an overload and short circuit protection circuit in a contactor DC starting control circuit to solve the above problems.

[0007] An overload and short circuit protection circuit in a contactor DC starting control circuit, comprising a rectifier bridge, a voltage stabilizing power supply, a starting circuit and a control circuit, one end of the rectifier bridge is connected with a power supply, the other end of the rectifier bridge is connected with a first capacitor, the first capacitor is connected with the starting circuit and the voltage stabilizing power supply, the starting circuit is connected with the control circuit and an AC contactor through a relay contact, one end of the voltage stabilizing power supply is connected with the AC contactor.

[0008] Preferably, one end of the voltage stabilizing power supply is connected with one end of a first diode, one end of a relay and the control circuit.

[0009] Preferably, the other end of the voltage stabilizing power supply is connected with a first resistor, an emitter of a triode and one end of a third capacitor.

[0010] Preferably, the other end of the first resistor is connected with the other end of the first diode, the other end of the first resistor is connected with the base of the triode through the second resistor, the collector of the triode is connected with the relay.

[0011] Preferably, the collector of the triode is connected with the reverser through the third diode and the fourth resistor respectively, the reverser is connected with the base of the triode through the second diode, and the other end of the third capacitor is connected with the reverser.

[0012] Preferably, the voltage stabilizing power supply is also connected with the low-voltage direct current through the fifth resistor and the sixth resistor.

[0013] Preferably, the fifth resistor and the sixth resistor are connected in series, and the middle point provides a threshold voltage value for the voltage comparator; the transformer is connected with the signal processor and the control circuit.

[0014] Compared with the prior art (the AC contactor has no overload and short-circuit tripping function), the utility model has the beneficial effects that: the utility model is provided with a rectifier bridge, a voltage stabilizing power supply, a starting circuit and a control circuit, and realizes the function of overload and short-circuit tripping of the AC contactor; when the main contact transmission loop of the AC contactor is overloaded or short-circuited, the voltage at the comparison input end of the voltage comparator sent by the transformer rises and is higher than the preset threshold voltage value of the voltage comparator, the output end of the voltage comparator becomes low voltage, the output end of the control circuit is turned off, the AC contactor is tripped, and the line is protected. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is the overload and short-circuit protection circuit diagram of the utility model; DETAILED DESCRIPTION

[0016] It should be noted that the embodiments in the utility model and the features in the embodiments can be combined with each other without conflict.

[0017] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0018] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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 utility model based on the specific circumstances.

[0019] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0020] like Figure 1 As shown, an overload and short-circuit protection circuit in a contactor DC starting control circuit includes a rectifier bridge ZM1, a regulated power supply A1, a starting circuit U1, and a control circuit A3. Two ends of the rectifier bridge ZM1 are connected to an external AC power supply Z1, and the other two ends of the rectifier bridge ZM1 are respectively connected to a first capacitor C1. The first capacitor C1 is connected to the starting circuit U1 and the regulated power supply A1. The starting circuit U1 is connected to the control circuit A3 and the AC contactor Z2 through a relay contact JK1. One end of the regulated power supply A1 is connected to the AC contactor Z2.

[0021] Furthermore, one end of the regulated power supply A1 is connected to one end of the first diode D1, one end of the relay J1, and the control circuit A3.

[0022] Furthermore, the other end of the regulated power supply A1 is connected to the first resistor R1, the emitter of the transistor T1, and one end of the third capacitor C3.

[0023] Furthermore, the other end of the first resistor R1 is connected to the other end of the first diode D1, and the other end of the first resistor R1 is connected to the base of the transistor T1 through the second resistor R2. The collector of the transistor T1 is connected to the relay J1.

[0024] Furthermore, the collector of the transistor T1 is connected to the inverter A2 through the third diode D3 and the fourth resistor R4, respectively. The inverter A2 is connected to the base of the transistor D3 through the second diode D2. The other end of the third capacitor C3 is connected to the inverter A2.

[0025] Furthermore, the regulated power supply A1 is also connected to a low-voltage DC power supply via a fifth resistor R5 and a sixth resistor R6.

[0026] Furthermore, the fifth resistor R5 and the sixth resistor R6 are connected in series, with the midpoint providing the threshold voltage value for the voltage comparator A5. The current transformer L1 is connected to the signal processor A4 and the control circuit A3.

[0027] Compared with the prior art, the present invention has the following advantages: The present invention is equipped with a rectifier bridge ZM1, a regulated power supply A1, a starting circuit U1, and a control circuit A3 to realize the overload and short-circuit tripping function of AC contactor Z2; When an overload or short circuit occurs in the transmission circuit of the main contact of AC contactor Z2, the voltage sent by the current transformer L1 to the comparison input terminal of voltage comparator A5 rises and exceeds the preset threshold voltage value of voltage comparator A5, the output terminal of voltage comparator A5 becomes low voltage, the output terminal of control circuit A3 is turned off, and AC contactor Z2 trips to protect the line.

[0028] Working principle:

[0029] Working principle

[0030] 1. AC contactor engages

[0031] The rectifier bridge ZM1 rectifies the AC voltage into a high DC voltage V1. The regulated power supply A1 converts the input high DC voltage V1 into a low DC voltage V2. The reverse breakdown characteristic of the first diode (Zenith diode) D1 is used to measure the low DC voltage V2 of the regulated power supply A1 after power-on. After the first diode D1 reverse breaks down, the voltage rises. When it rises to more than 0.7V, the transistor T1 conducts, the relay J1 closes the contact JK1, and the high DC voltage V1+ forms a large current loop through the starting circuit, through the relay contact JK1, and through the AC contactor coil to the negative terminal of V1, and the AC contactor Z2 is energized.

[0032] 2: AC contactor holding

[0033] After transistor T1 is turned on, the collector voltage of transistor T1 changes from high level to low level. The third capacitor C3 discharges through the fourth resistor R4 (the discharge time is longer than the holding time of the AC contactor). When the input voltage of inverter A2 drops to the hysteresis threshold voltage of inverter A2, the output voltage of inverter A2 changes from low level to high level, and the output voltage of inverter A3 changes from high level to low level. The second diode D2 conducts and pulls down the base voltage of transistor T1, transistor T1 is cut off, relay J1 is released, relay contact JK1 is opened, and the starting circuit exits operation. Since the low DC voltage of DC voltage V2 has been delivered to the control circuit A3, i.e., the AC contactor coil, and provides holding energy for AC contactor Z2, AC contactor Z2 will continue to remain in the holding state.

[0034] Three: AC contactor disconnected

[0035] When the mains power supply Z1 is disconnected, the DC low voltage V2 generated by the regulated power supply A1 will disappear to 0, and the AC contactor Z2 will disconnect because the coil does not have the required energy.

[0036] 4. Overload and short circuit AC contactor trip protection

[0037] The current transformer L1 is used for current detection in the main contact transmission circuit of AC contactor Z2. It detects the current quality and generates an applicable low AC voltage. The signal is processed by the signal processor A4 and sent to the comparison input terminal of the voltage comparator A5. When the input value of the voltage comparator A5 is lower than the preset threshold voltage comparison value of the voltage comparator A5, the output terminal of the voltage comparator A5 is high voltage, and the control circuit A3 outputs normally.

[0038] When an overload or short circuit occurs in the main contact transmission circuit of AC contactor Z2, the voltage sent by transformer L1 to the comparison input terminal of voltage comparator A5 rises and exceeds the preset threshold voltage value of voltage comparator A5. The output terminal of voltage comparator A5 becomes low voltage, the output terminal of control circuit A3 is turned off, and AC contactor Z2 trips to protect the line.

[0039] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. Any equivalent structural or procedural transformations made based on the content of the present utility model specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present utility model.

Claims

1. An overload and short circuit protection circuit in a contactor DC start control circuit, characterized in that: The application relates to a power supply device, which comprises a rectifier bridge (ZM1), a voltage stabilizer (A1), a starting circuit (U1) and a control circuit (A3), wherein two ends of the rectifier bridge (ZM1) are connected with a power supply (Z1), the other two ends of the rectifier bridge (ZM1) are connected with a first capacitor (C1) respectively, the first capacitor (C1) is connected with the starting circuit (U1) and the voltage stabilizer (A1) respectively, the starting circuit (U1) is connected with a control circuit (A3) and an AC contactor (Z2) through a relay contact (JK1), and one end of the voltage stabilizer (A1) is connected with the AC contactor (Z2).

2. An overload and short circuit protection circuit in a contactor DC start control circuit as set forth in claim 1, characterized in that: One end of the voltage stabilizer (A1) is connected with one end of a first diode (D1), one end of a relay (J1) and the control circuit (A3) respectively.

3. An overload and short circuit protection circuit for a contactor DC start control circuit as defined in claim 2, characterized in that: The other end of the voltage stabilizer (A1) is connected with a first resistor (R1), an emitter of a triode (T1) and one end of a third capacitor (C3) respectively.

4. An overload and short circuit protection circuit for a contactor DC start control circuit as set forth in claim 3, characterized in that: The other end of the first resistor (R1) is connected with the other end of the first diode (D1), the other end of the first resistor (R1) is connected with a base of the triode (T1) through a second resistor (R2), and a collector of the triode (T1) is connected with the relay (J1).

5. An overload and short circuit protection circuit for a contactor DC start control circuit as defined in claim 4, wherein: The collector of the triode (T1) is connected with an inverter (A2) through a third diode (D3) and a fourth resistor (R4) respectively, the inverter (A2) is connected with a base of a triode (D3) through a second diode (D2), and the other end of the third capacitor (C3) is connected with the inverter (A2).

6. An overload and short circuit protection circuit for a contactor DC start control circuit as set forth in claim 5, characterized in that: The voltage stabilizer (A1) is also connected with a direct-current low voltage through a fifth resistor (R5) and a sixth resistor (R6).

7. An overload and short circuit protection circuit for a contactor DC start control circuit as defined in claim 6, characterized in that: The fifth resistor (R5) and the sixth resistor (R6) are connected in series, a threshold voltage value of a voltage comparator (A5) is provided at a middle point, and a mutual inductor (L1) is connected with a signal processor (A4) connected with the control circuit (A3).

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