Circuit capable of suppressing surge voltage between contacts of relay during action

Abstract

The utility model discloses a circuit capable of inhibiting surge voltage between contacts when a relay acts. The circuit comprises a relay, a resistor, a piezoresistor, a diode, a direct current electromagnetic coil and a binding post. When a high-capacity inductive load in a circuit loses power, a relatively high reverse electromotive force, namely a surge voltage, is generated. A resistor-diode series follow current loop and a piezoresistor-diode series surge suppression loop are reversely connected in parallel to the two ends of an inductive load, when the load loses power and generates reverse electromotive force, the follow current loop eliminates or reduces the electromotive force, and the surge suppression loop is conducted and shunted when the electromotive force exceeds a threshold value, so that surge voltage is prevented from being generated through dual protection; and a relay contact and a circuit are protected. The scheme is a passive suppression protection circuit, has the advantages of simple structure, low cost, fast response, recoverability, dual protection and the like, and improves the operation stability and reliability of equipment.

Description

Technical Field

[0001] The utility model relates to the field of relay control circuits, and particularly relates to a circuit capable of suppressing surge voltage between contacts when a relay operates. Background Art

[0002] When a circuit is turned on or off an inductive load or a large load, a very high operating overvoltage will be generated. This instantaneous overvoltage is called surge voltage and is a kind of transient interference. This momentary overvoltage exceeding the normal operating voltage has a fast rising speed and a short duration, similar to a severe pulse.

[0003] Surges may not only damage components in the power supply and the circuit, but also affect the stability and reliability of the entire system. Therefore, when designing a circuit and selecting equipment, it is necessary to fully consider surge suppression and protection measures.

[0004] Surge voltage is a common transient voltage fluctuation in a circuit. Due to its high peak value and short time characteristics, surges may damage a relay, especially causing arc and oxidation corrosion to the relay contacts, thereby affecting the working stability and lifespan of the relay.

[0005] Specifically, for the ablation of relay contacts: when the current generated by the surge voltage passes through the relay contacts, it will cause the surface temperature of the contacts to rise rapidly instantaneously, resulting in the evaporation and ablation of the surface material of the contacts; for the oxidation of relay contacts: the surge current will cause arcs and electrical waves to be generated in the relay contacts and the coil. These arcs and electrical waves can generate a high-temperature area around the contacts, leading to oxidation corrosion and the adhesion and welding of the contacts. Therefore, how to effectively reduce or even eliminate the surge voltage and protect the relay contacts has become an urgent problem to be solved. Summary of the Utility Model

[0006] The purpose of the utility model is to overcome one or more deficiencies of the prior art, and provides a circuit capable of suppressing surge voltage on the contacts when a relay operates.

[0007] The purpose of the utility model is achieved by the following technical solutions:

[0008] A circuit capable of suppressing surge voltage between contacts when a relay operates, the circuit includes: three normally open contacts of relay #B4, namely the first group of normally open contacts 13-14, the second group of normally open contacts 23-24, and the third group of normally open contacts 33-34; resistor R1, varistor Z1, first diode D1, second diode D2, DC electromagnetic coil BRAKE1, DC electromagnetic coil BRAKE2, terminal T11, and terminal T12;

[0009] Among them, after the DC electromagnetic coils BRAKE1 and BRAKE2 are connected in series, one end is connected to the positive terminal T11, and is connected in series with the first set of normally open contacts 13-14 and the second set of normally open contacts 23-24 connected in series by the relay #B4 and then connected to the positive pole DC+ of the power supply; the other end is connected to the negative terminal T12, and is connected to the negative pole DC- of the power supply through the third set of normally open contacts 33-34 of the relay #B4;

[0010] Among them, a freewheeling circuit in which the resistor R1 and the first diode D1 are connected in series is connected in parallel across the two ends of the DC electromagnetic coil. The negative electrode of the first diode D1 is connected to the positive terminal T11, and the resistor R1 is connected to the negative terminal T12;

[0011] Among them, a surge suppression circuit formed by connecting the varistor Z1 and the second diode D2 in series is also connected in parallel across the two ends of the DC electromagnetic coil. The negative electrode of the second diode D2 is connected to the positive terminal T11, and the varistor Z1 is connected to the negative terminal T12.

[0012] Furthermore, the freewheeling circuit in which the resistor R1 and the first diode D1 are connected in series is reversely connected in parallel across the two ends of the DC electromagnetic coil BRAKE1 and the DC electromagnetic coil BRAKE2. When the contacts of the relay #B4 are disconnected and the DC electromagnetic coils BRAKE1 and BRAKE2 lose power, it is used to eliminate or reduce the back electromotive force by forming a freewheeling effect.

[0013] Furthermore, the surge suppression circuit formed by connecting the varistor Z1 and the second diode D2 in series is reversely connected in parallel across the two ends of the DC electromagnetic coil BRAKE1 and the DC electromagnetic coil BRAKE2. When the contacts of the relay #B4 are disconnected and the DC electromagnetic coils BRAKE1 and BRAKE2 lose power, the back electromotive force rises relatively fast. When it exceeds the threshold value of the varistor Z1, it is used to suppress the continuous rapid rise of the back electromotive force, avoid the generation of surge voltage, and protect the relay contacts and the circuit.

[0014] Furthermore, the freewheeling circuit in which the resistor R1 and the first diode D1 are connected in series and the surge suppression circuit formed by connecting the varistor Z1 and the second diode D2 in series are simultaneously reversely connected in parallel across the two ends of the DC electromagnetic coil BRAKE1 and the DC electromagnetic coil BRAKE2, which is used to achieve double protection.

[0015] The beneficial effects of the present utility model are:

[0016] 1. This protection circuit is a passive suppression protection circuit, with a simple structure, low cost, and easy to implement;

[0017] 2. The surge suppression circuit of this design has a fast response action and is recoverable;

[0018] 3. A dual protection circuit is designed to make the equipment applying this circuit more stable, safe and reliable. Description of the Drawings

[0019] Figure 1 It is a circuit diagram that can suppress the surge voltage between the contacts of a relay when it operates;

[0020] Figure 2 It is a measured graph of the surge voltage between the contacts of a relay in the case of an unprotected circuit in the embodiment;

[0021] Figure 3 It is a measured graph of the voltage between the contacts of a relay under the protection of a freewheeling circuit with a bypass and a surge suppression circuit in the embodiment. Detailed Embodiment

[0022] Next, the technical solution of the present utility model will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present utility model.

[0023] Refer to Figure 1 , this embodiment discloses a circuit that can suppress the surge voltage between the contacts of a relay when it operates.

[0024] This circuit is used for the control of an elevator. This circuit is a part of the control circuit of the elevator traction machine brake, and includes a freewheeling circuit in which a resistor and a diode are connected in series and are reversely connected in parallel with the inductive load, and a surge suppression circuit formed by a varistor and a diode connected in series.

[0025] Among them, the freewheeling circuit in which the resistor and the diode are connected in series is connected in parallel across the inductive load. When the relay contacts are disconnected, that is, when the inductive load loses power, since the current flowing through the inductor coil cannot change suddenly, a relatively high reverse electromotive force will be generated at this time. In DC applications, the freewheeling circuit in which the resistor and the diode are connected in series conducts to form a freewheeling current to eliminate or reduce the reverse electromotive force.

[0026] Among them, the surge suppression circuit formed by the varistor and the diode connected in series is also connected in parallel across the inductive load. When the reverse electromotive force continues to rise rapidly and exceeds the threshold of the varistor, the surge suppression circuit conducts to suppress the continuous rapid rise of the reverse electromotive force, avoid generating a surge voltage, and protect the relay contacts and the circuit.

[0027] Among them, BRAKE1 and BRAKE2 are the DC electromagnetic coils of the elevator traction machine brake. #B4 is the control relay of the traction machine brake coil. The resistor R1 and the diode D1 are connected in series to form a freewheeling circuit, and the varistor Z1 and the diode D2 are connected in series to form a surge suppression circuit. The DC power supply DC+ and DC- supply power to the brake.

[0028] When the three pairs of normally open contacts 13-14, normally open contacts 23-24, and normally open contacts 33-34 of the relay #B4 are closed, the DC power supply DC+ and DC- are connected, and the DC electromagnetic coils BRAKE1 and BRAKE2 of the traction machine brake are excited, and the brake is opened, and the elevator runs. At this time, due to the reverse cut-off effect of the diodes D1 and D2, the bypass freewheeling circuit and surge suppression circuit are both in an open state and do not affect the connection of the brake coil.

[0029] Refer to Figure 2 , when the elevator stops, it is necessary to disconnect the three pairs of normally open contacts, namely normally open contacts 13-14, normally open contacts 23-24, and normally open contacts 33-34 of the relay #B4. The coils BRAKE1 and BRAKE2 of the traction machine brake lose power, and the brake closes. If there is no protection of the bypass freewheeling circuit and surge suppression circuit, at the moment when the three pairs of normally open contacts of the relay #B4 are disconnected, since the current flowing through the inductive coil cannot change suddenly, a relatively high reverse electromotive force will be generated, forming a surge voltage and generating an arc between the contacts of the relay #B4, damaging the relay contacts.

[0030] Refer to Figure 3 , if there is protection of the bypass freewheeling circuit and surge suppression circuit, at the moment when the three pairs of normally open contacts of the relay #B4 are disconnected, since the current flowing through the inductive coils BRAKE1 and BRAKE2 cannot change suddenly, a relatively high reverse electromotive force will be generated. B10 is + and B20 is -, and the freewheeling circuit in which the resistor R1 and the diode D1 are connected in series across the load is turned on to eliminate or reduce the reverse electromotive force. If this reverse electromotive force rises rapidly and exceeds the threshold of the varistor Z1, the surge suppression circuit in which the varistor Z1 and the diode D2 are connected in series across the load is turned on, and the overcurrent is shunted to this bypass, thereby suppressing the continuous rapid rise of the reverse electromotive force and avoiding the generation of surge voltage to protect the relay contacts and the circuit.

[0031] A varistor, abbreviated as VDR, is a non-linear overvoltage protection semiconductor component sensitive to voltage, and its resistance value decreases sharply with the increase of voltage. When the voltage applied to the varistor is lower than the threshold of the varistor, the current flowing through the varistor is extremely small, and the varistor is equivalent to a resistor with an infinite resistance value. When the voltage applied to the varistor is lower than its threshold, the varistor is equivalent to a switch in the off state. When the voltage applied to the varistor exceeds the threshold of the varistor, the current flowing through the varistor surges, and the varistor is equivalent to a resistor with an infinitesimal resistance value. That is to say, when the voltage applied to the varistor is higher than its threshold, the varistor is equivalent to a switch in the closed state.

[0032] Since the current flowing through an inductive coil cannot change suddenly, a relatively high back electromotive force, i.e., a surge voltage, will be generated when the inductive load is disconnected. In DC applications, a freewheeling circuit consisting of a resistor and a diode in series can be connected in parallel across the load to eliminate or reduce the back electromotive force. If this back electromotive force rises rapidly and exceeds the threshold of the varistor, the surge suppression circuit consisting of the varistor and the diode conducts, shunting the overcurrent to this bypass, thereby suppressing the continuous rapid rise of the back electromotive force and avoiding the generation of surge voltage to protect the relay contacts and the circuit.

[0033] When the inductive load is connected, due to the reverse cut-off effect of the diode, both the freewheeling circuit of the bypass and the surge suppression circuit are in the open state, which does not affect the connection of the inductive load.

[0034] The utility model is mainly applied to a circuit where the relay controls a large-capacity inductive load, which can suppress the generation of surge voltage between the relay contacts and protect the relay contacts. Specifically, when the relay contacts are disconnected, that is, when the inductive load loses power, it can play a role in suppressing the surge voltage and protecting the relay contacts.

[0035] By connecting protection circuits in parallel across the two ends of a large-capacity inductive load, namely a freewheeling circuit consisting of a resistor and a diode in series, and a surge suppression circuit consisting of a varistor and a diode in series, double protection can be achieved.

[0036] The above description is only the preferred embodiment of the utility model. It should be understood that the utility model is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments. Instead, it can be used in various other combinations, modifications and environments, and can be changed within the scope of the concept described herein through the above teachings or the technology or knowledge in related fields. And any changes and modifications made by those skilled in the art without departing from the spirit and scope of the utility model shall fall within the protection scope of the appended claims of the utility model.

Claims

1. A circuit capable of suppressing surge voltage between contacts of a relay when the relay is in operation, characterized in that: The circuit includes: three groups of normally open contacts of relay #B4, namely, a first group of normally open contacts 13-14, a second group of normally open contacts 23-24, and a third group of normally open contacts 33-34; a resistor R1, a varistor Z1, a first diode D1, a second diode D2, a DC electromagnetic coil BRAKE1, a DC electromagnetic coil BRAKE2, a terminal T11, and a terminal T12; Among them, after the DC electromagnetic coils BRAKE1 and BRAKE2 are connected in series, one end is connected to the positive terminal T11, and is connected to the positive pole DC+ of the power supply through the first group of normally open contacts 13-14 and the second group of normally open contacts 23-24 connected in series by relay #B4; the other end is connected to the negative terminal T12, and is connected to the negative pole DC- of the power supply through the third group of normally open contacts 33-34 of relay #B4; The freewheeling circuit of the resistor R1 and the first diode D1 connected in series is connected in parallel to the two ends of the DC electromagnetic coil, the cathode of the first diode D1 is connected to the anode terminal T11, and the resistor R1 is connected to the cathode terminal T12; Among them, the surge suppression circuit formed by the varistor Z1 and the second diode D2 in series is also connected in parallel to the two ends of the DC electromagnetic coil, the cathode of the second diode D2 is connected to the positive terminal T11, and the varistor Z1 is connected to the negative terminal T12.

2. A circuit capable of suppressing surge voltage between contacts of a relay when the relay is in operation according to claim 1, characterized in that: The freewheeling circuit formed by the resistor R1 and the first diode D1 in series is reversely connected in parallel at both ends of the DC electromagnetic coil BRAKE1 and the DC electromagnetic coil BRAKE2. When the contact of the relay #B4 is disconnected and the DC electromagnetic coil BRAKE1 and the DC electromagnetic coil BRAKE2 lose power, it is used to eliminate or reduce the reverse electromotive force by forming a freewheeling effect.

3. A circuit capable of suppressing surge voltage between contacts of a relay when the relay is in operation according to claim 1, characterized in that: The surge suppression circuit formed by the varistor Z1 and the second diode D2 in series is reversely connected in parallel at both ends of the DC electromagnetic coil BRAKE1 and the DC electromagnetic coil BRAKE2. When the contact of the relay #B4 is disconnected and the DC electromagnetic coil BRAKE1 and the DC electromagnetic coil BRAKE2 lose power, the reverse electromotive force rises rapidly. When it exceeds the threshold value of the varistor Z1, it is used to suppress the reverse electromotive force from continuing to rise rapidly.

4. A circuit capable of suppressing surge voltage between contacts of a relay when it is actuated according to claim 1, characterized in that: The freewheeling circuit formed by the series connection of the resistor R1 and the first diode D1, and the surge suppression circuit formed by the series connection of the varistor Z1 and the second diode D2 are simultaneously connected in reverse parallel at both ends of the DC electromagnetic coil BRAKE1 and the DC electromagnetic coil BRAKE2 to achieve double protection.

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