CN102768924B - An undervoltage release with low power consumption and suitable for three-phase power supply - Google Patents

Abstract

The invention relates to a low-power consumption under-voltage release suitable for a three-phase power supply, which comprises: the system comprises an electromagnet coil, an armature, a rectifying circuit, a voltage reduction circuit, a relay, a line voltage detection module, a sampling circuit and a main control module, wherein a rated voltage Ue and a voltage value of strong start are stored, and the voltage reduction circuit is used for collecting the output voltage and the voltage period of each line voltage detection module to calculate each line voltage effective word of the three-phase power supply; and if the effective value of any line voltage is lower than 50% of the rated voltage Ue, controlling the switch circuit to be switched off.

Description

An undervoltage release with low power consumption and suitable for three-phase power supply

technical field

The invention relates to an undervoltage release device with low power consumption and suitable for three-phase power supply.

Background technique

The undervoltage release is one of the important components of circuit breakers, especially frame circuit breakers. The undervoltage release is a release that makes the circuit breaker disconnect with or without delay when its terminal voltage drops to a certain range. When the power supply voltage drops (even slowly) to the rated operating Within the range of 70% to 35% of the voltage, the undervoltage release should act (the coil of the release is de-energized, and the movable armature in the coil is pushed out by the return spring—tripping), and the undervoltage release will trip when the power supply voltage is equal to When the rated operating voltage of the undervoltage release is 35% of the rated operating voltage, the undervoltage release should be able to prevent the circuit breaker from closing; when the power supply voltage is equal to or greater than 85% of the rated operating voltage of the undervoltage release, it should be able to ensure that the circuit breaker Reliable closing (the coil of the release is energized, and the movable armature in the coil has the coil electromagnetic force to overcome the spring force to absorb and maintain a certain torque—"pulling in", which provides conditions for reliable closing of the circuit breaker). The essence of undervoltage tripping is an effective measure to prevent the self-heating of the electrical equipment itself from aggravating after the electrical equipment of the lower level of the circuit breaker works under the undervoltage state and the current is too large.

With reference to the above principles, most of the existing undervoltage releases work in the single-phase power supply mode. The integrated undervoltage release in the three-phase circuit has not yet seen a relatively mature undervoltage release solution and product.

Moreover, the circuit design of the existing undervoltage release is mostly simple or imperfect. In the occasions where the interference is serious, especially the circuit breaker near the intermediate frequency application occasion, the undervoltage release is often interfered by the intermediate frequency and malfunctions. . Or when the frequency of the marine generator changes, the undervoltage release will malfunction due to the frequency change. The misoperation of the undervoltage release caused the misopening of the circuit breaker.

Contents of the invention

The technical problem to be solved by the present invention is to provide an undervoltage release suitable for three-phase power supply with quick start and low power consumption.

In order to solve the above technical problems, the present invention provides an undervoltage release with low power consumption and suitable for three-phase power supply, including: an electromagnet coil, an armature controlled by the electromagnet coil; a rectifier circuit, the input terminal of which is connected to the Any line voltage in the three-phase power supply is connected; the step-down circuit, its input terminal is connected with the positive output terminal of the rectifier circuit, and its output terminal is connected with the current input terminal of the electromagnet coil, which is used to maintain the armature pull-in The voltage; the relay, its pair of normally open contacts are respectively connected with the output end of the rectifier circuit and the current input end of the electromagnet coil; the switch circuit, the current output end of the electromagnet coil is connected with the current input end of the switch circuit The input ends are connected; the line voltage detection module is set at the output end of the three-phase power supply and is used to detect at least two sets of line voltages; the sampling circuit is used to detect the output voltage of the rectification circuit; the main control module stores the rated The voltage Ue and the voltage value of the strong start are used to collect the output voltage of each line voltage detection module to calculate the effective word of each line voltage of the three-phase power supply, when the effective value of each line voltage of the three-phase power supply is simultaneously When it reaches 80% of the rated voltage Ue, and the sampling voltage of the sampling circuit reaches the voltage value of the strong start, the normally open contact is first controlled to be closed, and then the switch circuit is controlled to be turned on. , and then control the normally open contact to disconnect; if the effective value of any line voltage is lower than 50% of the rated voltage Ue, control the switch circuit to disconnect.

Further, the main control module is further configured to: obtain the frequency or period of the line voltage of the three-phase power supply according to the rising edge or falling edge of the output voltage of each line voltage detection module, so as to calculate the three-phase The effective value of each line voltage of the power supply. The present invention first detects the sampled voltage value and cycle output by the line voltage detection module circuit through the main control module to obtain the accurate effective value of the line voltage of the external network (that is, the three-phase power supply), and can more accurately judge the voltage of the external network Whether the effective value of the line voltage reaches 80% of the rated voltage Ue, so the release is also very suitable for applications with different frequencies, especially for AC voltages with a frequency of 20Hz to 65Hz. Therefore, the second technical problem that can be solved is to provide an undervoltage release that is anti-harmonic and suitable for multi-frequency three-phase power supply.

Further, in order to more effectively reduce the current when the electromagnet coil is short-circuited and avoid circuit burnout, a step-down capacitor CK is set at the input end of the rectifier circuit, and the capacitive reactance of the step-down capacitor CK makes the short-circuit current smaller .

Further, in order to better avoid the interference of the harmonics in the grid to the release, an EMC (electromagnetic compatibility) power filter is provided at the input end of the rectification circuit. EMC power filter, also known as "Electromagnetic Compatibility Filter", is mainly used in instruments and automation control systems to suppress and eliminate strong electromagnetic interference and spark interference at the site of industrial automation systems, and to correct field instruments and meters. Ensure the safe and reliable operation of the automation control system

Further, in order to obtain a high voltage for the electromagnetic coil, a strong starting capacitor C1 is set at the input end of the step-down circuit, and the charging voltage is equal to the input AC voltage times (about 3-5 times the rated operating voltage of the solenoid coil). The moment the switching circuit is turned on, all the charges on the energy storage capacitor C1 are released through the electromagnetic coil to achieve the purpose of "strong start" attraction.

In order to avoid the interference of the peripheral power grid to the weak current signal, the line voltage detection module includes: a step-down circuit connected to the line voltage, a photocoupler connected to the output end of the step-down circuit, the output end of the photocoupler circuit is connected to the connected to the main control module.

The main control module can be any type of single chip microcomputer (MCU), system on chip (SOC), CPLD, FPGA or ARM and DSP.

Furthermore, in order to be used in occasions that require delayed tripping, the main control module is a single-chip microcomputer circuit, which includes: a BCD dial switch connected to the single-chip microcomputer and suitable for setting and controlling the delayed disconnection time of the switching circuit.

Further, the main control module, the switch circuit, and the power supply of the relay are all provided by the step-down circuit.

Further, in order to prevent the reverse flow of the VH voltage, on the other hand, prevent the counter electromotive force generated by the electromagnet coil at the moment when the normally open contact is disconnected, so as to protect the step-down circuit. The undervoltage release also includes a diode D2, the anode of the diode D2 is connected to the output end of the step-down circuit, and the cathode thereof is connected to the input end of the electromagnet coil.

A working method of an anti-harmonic, multi-frequency undervoltage release suitable for three-phase power supply, comprising:

① When the undervoltage release is connected to the three-phase power supply, the main control module detects and calculates the effective value of each line voltage of the three-phase power supply through the line voltage detection module;

② When the voltage of each line reaches 80% of the rated voltage Ue at the same time, the main control module samples and collects the output voltage of the rectifier circuit, if the output voltage reaches the voltage value of the strong start , the main control module first controls the normally open contact of the relay connected between the output terminal of the rectifier circuit and the current input terminal of the electromagnet coil to close, and then controls the relay to be connected to the current output terminal of the electromagnet coil The switching circuit of the switch is turned on, so that the electromagnet coil is energized, that is, the armature is attracted;

Then, the normally open contact is controlled to be disconnected, that is, only the step-down circuit provides the voltage to maintain the pull-in of the armature;

③ When any line voltage is lower than 50% of the rated voltage Ue, the main control module controls the switch circuit to be disconnected, so that the electromagnet coil is de-energized, that is, the armature pops up.

Further, the method for judging the access of the electromagnet coil includes:

A: When the line voltage is normal, if the sampling voltage is not equal to the voltage value for maintaining the pull-in of the armature, the main control module controls the switch circuit to be disconnected;

B: When the sampling voltage returns to the strong starting voltage value, the main control module generates a pulse signal to control the conduction of the switch circuit to detect whether the electromagnet coil is connected;

C: When the sampling voltage drops, it is judged that the electromagnet coil has been connected, and when the sampling voltage reaches the voltage value of the strong start, the main control module controls the switch circuit to be turned on so that The solenoid coil is energized.

The present invention has the following advantages: (1) The relay is controlled by the step-down circuit to switch between starting and maintaining voltage, which overcomes the problem of high coil heat generation when the existing undervoltage release is in normal operation; through the connected strong starting capacitor C1, It overcomes the phenomenon of small starting torque and often non-adhesion, and makes the circuit design simple; (2) Through the line voltage detection module, two sets of line voltages are detected at the same time, and the voltage values of the three phase lines are obtained, and the input voltage is judged by the single-chip microcomputer Whether it reaches 80% of the rated voltage, the release works on the three-phase power supply by detecting the strong starting voltage, which solves the technical problem that the existing undervoltage release cannot work under the three-phase power supply; (3) adopts a single-chip microcomputer To carry out undervoltage control, which can effectively reduce power consumption; (4) The line voltage detection module adopted, which realizes the acquisition of SA and SB signals through photoelectric coupling, has a simple circuit and good isolation effect; The detection of the frequency of the power grid by the voltage detection module further obtains accurate effective values, which can ensure that the armature pulls in to reach a sufficient rated voltage, and broadens the use occasions of the release; (6) The acquisition of the frequency of the power grid can effectively remove the power grid The interference of medium harmonics, together with the EMC two-way filter power filter, can more effectively avoid harmonic interference in the power grid.

Description of drawings

In order to make the content of the present invention more easily understood, the present invention will be described in further detail below in conjunction with the specific embodiments according to the accompanying drawings, wherein

Fig. 1 is the circuit principle diagram of anti-harmonic of the present invention namely multi-frequency and the undervoltage release device that is applicable to three-phase power supply;

Fig. 2 is a circuit structure one of the line voltage detection module of the present invention;

Fig. 3 is the circuit structure two of the line voltage detection module of the present invention;

FIG. 4 is a graph showing the volt-ampere relationship of the optocoupler of the present invention.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the present invention is described in detail:

The parameter design of the AC shunt release of the present invention complies with the low-voltage switchgear and control equipment standards: GB14048.1-2006 and GB14048.2-2008 define the main technical parameters of the undervoltage release. Under the requirements of this standard, the following examples are given for illustration.

Example 1

As shown in Figure 1-2, an undervoltage release includes: an electromagnet coil 3, an armature controlled by the electromagnet coil 3; a rectifier circuit 1, the input end of which is connected to any line voltage in the three-phase power supply; Step-down circuit 2, its input end is connected with the positive output end of described rectifier circuit 1, its output end is connected with the current input end of described electromagnet coil 3, is used for providing the voltage that maintains armature pull-in; Relay 4, its A pair of normally open contacts are respectively connected to the output end of the rectifier circuit 1 and the current input end of the electromagnet coil 3; the switch circuit 7, the current output end of the electromagnet coil 3 is connected to the input of the switch circuit 7 The line voltage detection module is set at the output end of the three-phase power supply and is used to detect at least two groups of line voltages; the sampling circuit 5 is used to detect the output voltage of the rectification circuit 1; the main control module 8 stores There are rated voltage Ue and strong start-up voltage values, which are used to collect the output voltages of the line voltage detection modules 6 to calculate the effective values of the line voltages of the three-phase power supply, when the line voltages of the three-phase power supply When the effective value reaches 80% of the rated voltage Ue at the same time, and the sampling voltage of the sampling circuit 5 reaches the voltage value of the strong start, the normally open contact is first controlled to be closed, and then the switch circuit 7 is controlled to be turned on. After the armature is pulled in, the normally open contact is controlled to be disconnected; if the effective value of any line voltage is lower than 50% of the rated voltage Ue, the switch circuit 7 is controlled to be disconnected. The main control module 8 is also used to: obtain the frequency or period of the line voltage of the three-phase power supply according to the rising edge or falling edge of the output voltage of each line voltage detection module, so as to calculate the frequency of the three-phase power supply The effective value of each line voltage. The specific method is: the main control module opens the interrupt to detect the rising edge and falling edge of the line voltage detection module road output SA, SB signal, to obtain the cycle or frequency of the line voltage, and the sampling of the line voltage detection module road output The voltage value is calculated to obtain the accurate line-to-line voltage effective value of the external network, which can more accurately judge whether the effective value of the external network voltage reaches 80% of the rated voltage Ue, so the release is also very suitable for applications with different frequencies , especially suitable for AC voltage with a frequency of 20Hz ~ 65Hz.

A step-down capacitor CK and an EMC power filter are arranged at the input end of the rectification circuit 1 .

A strong starting capacitor C1 is provided at the output end of the rectification circuit 1 .

The line voltage detection module includes: a step-down circuit 6-1 connected to the line voltage, a photocoupler 6-2 connected to the output end of the step-down circuit, the output end of the optocoupler circuit 6-2 is connected to the The main control module 8 is connected.

The line voltage detection module can also use a rectifier circuit to connect with a voltage divider circuit, and take samples from the voltage divider to keep the linear relationship of the sampling voltage.

The step-down circuit also provides working power for the main control module, switch circuit and relay.

The main control module 8 is a single-chip microcomputer circuit, which includes: a BCD dial switch connected with the single-chip microcomputer, which is suitable for setting and controlling the delay time of switching off the switch circuit 7 .

The main control module 8 can be a single chip microcomputer (MCU), a system on chip (SOC), CPLD, FPGA or ARM and DSP.

Example 2

Referring to Figures 1-3, on the basis of Embodiment 1, the implementation of the main parts of the undervoltage release is described.

After the alternating current passes through the rectifying circuit 1, a full-wave pulsating voltage VH is formed to charge the strong start-up capacitor C1. The VH voltage is stepped down by the step-down circuit 2 to supply power to the main control module 8, and at the same time provide power to the relay 4 and the switch circuit 2. The voltage VO formed by the step-down circuit 2 is isolated by the diode D2 and the voltage VP is obtained. The electromagnet coil 3 is powered. The resistors R1 and R2 form a sampling circuit of VH, and the sampling signal SH is sent to the main control module 8 .

Wherein the line voltage detection module includes: a first line voltage detection module 6a and a second line voltage detection module 6b respectively connected between any two line voltages; The output voltage SA of the first-line voltage detection module (6a) and the output voltage SB of the second-line voltage detection module (6b) obtain the cycle time (frequency) of the power grid, and sample SA several times in one cycle, and apply FFT and other methods to solve Calculate the "effective value" of the corresponding grid line voltage, and according to the effective value, when it is judged to be greater than 80% of the nominal voltage (rated voltage), the main control module 8 further judges whether the voltage VH has reached a certain value at the same time. When these two conditions are all satisfied, the main control module 8 controls the relay to connect the contacts ①─② to provide a high starting voltage for the electromagnet coil 3, and then the main control module 8 controls the The switch circuit 2 turns on the electromagnet coil 3, and the electromagnet coil 3 realizes a strong start. After the strong start is completed, the main control module 8 controls the relay 4 to disconnect the contacts ①─②, and the voltage VP maintains a certain torque of the electromagnet coil 3 . When the effective value is less than 50% of the nominal voltage, the main control module 8 controls the switch circuit 2 to disconnect the current of the electromagnet coil 3, and the return spring inside the electromagnet coil 3 ejects the armature, and the armature Open the self-locking mechanism of the circuit breaker to realize the opening of the circuit breaker.

The isolation diode D1 is set after the full-wave rectification, so that the charging voltage (VH) on the strong starting capacitor C1 does not affect the information of the grid ripple voltage (SP). It provides convenience for analyzing the grid voltage cycle and harmonics.

In the present invention, the relay 4 first connects the contacts ①─②, and the starting voltage of the electromagnet coil 3 is the charging voltage (VH) of the strong starting capacitor C1, which is the input AC voltage times (several times the rated operating voltage of the electromagnet coil 3). At the moment when the switch circuit 2 is turned on, all the charges on the strong start capacitor C1 are released through the electromagnet coil 3 to achieve the purpose of "strong start" attraction. For the power of the strong start, the capacity of the strong start capacitor C1 can be further optimized by appropriately increasing the capacitance of the strong start capacitor C1 in addition to meeting the minimum requirements of the step-down circuit.

In the present invention, the current input terminal of the electromagnet coil 3 is fixedly connected to the voltage VP in advance, so as to prevent the electromagnet coil 3 from being disconnected automatically when the voltage is lost during the switching period of the contacts ①─②. After the electromagnet coil 3 is strongly started, the basic power of the electromagnet coil 3 is maintained by the voltage VP to meet the requirements of the low power operation of the electromagnet coil 3, which not only realizes high torque start, but also makes the undervoltage trip The overall calorific value of the buckle is small, and its circuit structure is simple.

In the present invention, the output voltage VO of the step-down circuit 2 is isolated by the diode D2 to form VP to supply power to the electromagnet coil 3. On the one hand, the diode D2 prevents the backflow of the VH voltage, and on the other hand prevents the contact ①── ② The counter electromotive force generated by the electromagnet coil 3 at the moment of disconnection protects the step-down circuit.

In the present invention, the input voltage is rectified by full wave, the isolation diode D1 charges the strong start C1 after isolation, and the step-down circuit generates 5V, 12V and VO voltages. These three groups of voltages have nothing to do with the frequency and harmonics of the input voltage.

In the present invention, the main control module 8 accurately analyzes the SA and SB signals to calculate the effective value of the grid line voltage through the grid cycle (frequency) obtained by the line voltage detection module, and the effective value corresponds to the cycle. According to the effective value, when it is judged that it is greater than 80% of the nominal voltage, the main control module 8 further judges whether VH has reached a certain value at the same time. When these two conditions are all satisfied, the main control module 8 controls the relay 4 to connect the contacts ①─② to provide a high starting voltage for the electromagnet coil 3, and then the main control module 8 The switch circuit 2 is controlled to turn on the electromagnet coil 3, and the electromagnet coil 3 realizes a strong start and ensures 100% pull-in.

Example 3

See Figure 1-4, on the basis of Embodiment 1-2, taking 330V voltage and the main control module 8 using a single-chip microcomputer circuit as an example, it shows that anti-harmonic and multi-frequency undervoltage are suitable for undervoltage tripping of three-phase power supply The implementation of the main part of the buckle.

The line voltage is connected to the two input ends of the rectification circuit 1 after EMC bidirectional filtering. The positive end of the rectification circuit 1 is defined as (VH), and the negative end is grounded (GND).

After power-on, the rectifier circuit 1 rectifies the AC voltage into a DC pulsating voltage SP, charges the strong start-up capacitor C1 through the isolation diode D1, and the charging voltage VH is equal to the input AC voltage times (80% effective value, approximately equal to 430V). The charging voltage has a voltage sampling circuit 5 composed of R1 and R2 in series, and the production sampling signal SH is sent to the single-chip microcomputer. Voltage VH powers the step-down circuit.

The 12V (15V) generated by the step-down circuit 2 is used by the switch circuit 7 and the relay 4, the generated 5V (3.3V) is used by the microcontroller circuit, and the generated VO (30V) is connected to the diode D2 anode. The cathode of the diode D2 is connected to one end of the electromagnet coil 3 and is marked as VP.

The main control module 8 interrupts the output voltage SA from the first line voltage detection module 6a and the output voltage SB from the second line voltage detection module 6b through the rising edge (or falling edge), obtains the grid cycle time (frequency), and in a Sampling SA several times in the cycle, using FFT and other methods to calculate the "effective value" of the corresponding grid line voltage, according to the effective value, when it is judged to be greater than 80% of the nominal voltage (rated voltage), the single-chip circuit further judges the voltage VH Whether it reaches a certain value at the same time (such as greater than 430V). When these two conditions are met, the single-chip microcomputer circuit controls the relay to connect the contacts ①─② to provide a high starting voltage for the electromagnet coil 3. After a delay (100ms), the single-chip microcomputer circuit controls the The switch circuit 2 is connected to the electromagnet coil 3, and the electromagnet coil 3 realizes a strong start. After the strong start is completed, continue to delay (100 ms), the single-chip circuit controls the relay 4 to disconnect the contacts ①─②, and the voltage VP maintains a certain torque of the electromagnet coil 3 . When the effective value is less than 50% of the nominal voltage, the single-chip microcomputer circuit controls the switch circuit 2 to disconnect the current of the electromagnet coil 3, and the return spring inside the electromagnet coil 3 ejects the armature, and the armature pushes away. The circuit breaker self-locking mechanism realizes the opening of the circuit breaker.

The single-chip microcomputer circuit includes the auxiliary circuit including the dial switch. In the case where a delay trip is required, different combinations of the dial switch are set. After the single-chip microcomputer reads this signal, the delay time of the delay trip is determined. For example, the three-digit BCD code DIP switch represents a delay of 0 seconds, 1 second, 2 seconds, 3 seconds, 4 seconds, 5 seconds, 10 seconds, 20 seconds, or other time values. Among them, the delay of 0 seconds means (no delay) "instantaneous disconnection", and 10 seconds means that when the input voltage is less than 50% of Ue, it will be disconnected after a delay of 10 seconds.

In order to further illustrate the working principle of the phase voltage detection module, the implementation of the main links of the three-phase undervoltage release is described.

Assume that the first line voltage detection module 6a is connected to A-B. One end of the resistor R3 is connected to the A phase, and the other end is connected to an input end of the second rectifier bridge B2. The other input terminal of the second rectifier bridge B2 is connected to the B phase. The positive terminal of the output of the second rectifier bridge B2 is connected to the anode of the input terminal of the optocoupler 6-2, and the negative terminal of the output of the second rectifier bridge B2 is connected to the cathode of the input terminal of the optocoupler 6-2. The collector of the output terminal of the photocoupler 6-2 is connected to 5V, the emitter is connected to the resistor R4, and connected to the single-chip microcomputer. The other end of R4 is grounded. The optocoupler 6-2 may be a linear optocoupler, such as a PC817 whose transfer characteristic is a monotonic function.

The present invention focuses on detecting the voltage values at the two points of "pull-in" and "release (tripping)", and by selecting appropriate resistance values of R3 and R4, the optocoupler 6-2 can be kept linear to meet the voltage The need for accurate detection, see Figure 4. Assuming that the input voltage is 50% of Ue, the output voltage SA is 1V, corresponding to point a; assuming that the input voltage is 80% of Ue, the output voltage SA is 3.8V, corresponding to point b. Then this simple isolation detection circuit fully meets the detection requirements of undervoltage tripping. In addition, when a phase failure occurs, the output voltage SA is 0V, and the single-chip microcomputer can easily distinguish whether a phase failure occurs.

Example 4

On the basis of Embodiment 1-3, the main control module 8 calculates the "effective value" of the corresponding grid voltage by obtaining the sampling voltages SA and SB respectively through the first and second line voltage detection modules, The main control module opens the rising edge or falling edge interrupt to obtain the frequency corresponding to the SA and SB signals, thereby obtaining the cycle of the line voltage, and within one cycle, divide the cycle time by 32 to obtain the sampling time, (for example, the power grid The frequency is 50Hz, and the period time is 20ms. After full-wave rectification, it is divided into 2 positive half-waves, and each positive half-wave period is 10ms. 10ms/32==0.3125ms=312us), according to this interval, point-by-point sampling is formed. 32-point database.

The specific "effective value" of the grid line voltage can be further calculated by the following two methods:

Method 1. Use the FFT algorithm (Fourier algorithm), use the 32-point database to "extract" the primary wave (fundamental wave), and use the fundamental wave to judge whether it is greater than 80%; this algorithm resists complex waveforms after interference, especially against severe interference The effect of the waveform is ideal.

The second method is to use the effective value algorithm, that is, Wherein ui is the instantaneous value of the input AC voltage, and the loss value can be obtained by compensating with the sampling signal input to the main control module 8; the algorithm is against waveforms whose high-order harmonics are not serious (THD total harmonic distortion is less than 15 %), the effect is ideal.

Example 5

See Figure 1-2, on the basis of Embodiment 1-4, a working method of an undervoltage release that is anti-harmonic, multi-frequency and suitable for three-phase power supply, including:

① After the undervoltage release is connected to the three-phase power supply, the main control module 8 detects and calculates the effective value of each line voltage of the three-phase power supply through the line voltage detection module 6;

② When the voltages of each line reach 80% of the rated voltage Ue at the same time, the main control module 8 samples and collects the output voltage of the rectifier circuit 1, if the output voltage reaches the threshold of the strong start voltage value, the main control module 8 first controls the normally open contact of the relay 4 connected between the output terminal of the rectifier circuit 1 and the current input terminal of the electromagnet coil 3 to close, and then controls the contact with the electromagnet The switch circuit 7 connected to the current output end of the coil 3 is turned on, so that the electromagnet coil 3 is energized, that is, the armature is attracted;

Then, the normally open contact is controlled to be disconnected, that is, only the step-down circuit 2 provides the voltage to maintain the pull-in of the armature;

③ When any line voltage is lower than 50% of the rated voltage Ue, the main control module 8 controls the switch circuit 7 to turn off, so that the electromagnet coil 3 is de-energized, that is, the armature pops up.

The method for judging the access of the electromagnet coil 3 includes:

A: When the line voltage is normal, if the sampling voltage is not equal to the voltage value for maintaining the pull-in of the armature, the main control module 8 controls the switch circuit 7 to be disconnected;

B: When the sampling voltage returns to the voltage value of the strong start, the main control module 6 generates a pulse signal to control the conduction of the switch circuit 7 to detect whether the electromagnet coil 3 is connected;

C: When the sampling voltage drops, it is judged that the electromagnet coil 3 has been connected, and when the sampling voltage reaches the voltage value of the strong start, the main control module 6 controls the switch circuit 2 to conduct Pass through to make described electromagnet coil 3 energized.

Apparently, the above-mentioned embodiments are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And these obvious changes or modifications derived from the spirit of the present invention are still within the protection scope of the present invention.

Claims (10)

1. An undervoltage release, comprising: an electromagnet coil (3), an armature controlled by the electromagnet coil (3); it is characterized in that it also includes: A rectifier circuit (1), the input end of which is connected to any line voltage in the three-phase power supply; The step-down circuit (2), the input terminal of which is connected to the positive output terminal of the rectifier circuit (1), and the output terminal of which is connected to the current input terminal of the electromagnet coil (3), are used to provide the power to maintain the armature pull-in Voltage; A relay (4), a pair of normally open contacts connected to the output end of the rectifier circuit (1) and the current input end of the electromagnet coil (3) respectively; A switch circuit (7), the current output end of the electromagnet coil (3) is connected to the input end of the switch circuit (7); A line voltage detection module, located at the output end of the three-phase power supply, for detecting at least two sets of line voltages; A sampling circuit (5), used to detect the output voltage of the rectification circuit (1); The main control module (8), which stores the rated voltage Ue and the voltage value of the strong start, is used to collect the output voltage of each line voltage detection module (6) to calculate the effective value of each line voltage of the three-phase power supply, When the effective value of each line voltage of the three-phase power supply reaches 80% of the rated voltage Ue at the same time, and the sampling voltage of the sampling circuit (5) reaches the voltage value of the strong start, the normally open contact is first controlled to close, Then control the switching circuit (7) to be turned on, and then control the normally open contact to disconnect after the armature is pulled in; if the effective value of any line voltage is lower than 50% of the rated voltage Ue, then control the The switch circuit (7) is disconnected. 2. The undervoltage release according to claim 1, characterized in that: the main control module (8) is also used to: acquire the output voltage according to the rising or falling edge of the output voltage of each line voltage detection module The frequency or period of the line voltage of the three-phase power supply is used to calculate the effective value of each line voltage of the three-phase power supply. 3. The undervoltage release according to claim 2, characterized in that a step-down capacitor CK and an EMC power filter are provided at the input end of the rectification circuit (1). 4. The undervoltage release according to any one of claims 1-3, characterized in that a strong starting capacitor C1 is provided at the output end of the rectification circuit (1). 5. The undervoltage release according to claim 1, characterized in that: the line voltage detection module (6) includes: a line voltage step-down circuit (6-1) connected to the line voltage, and a step-down An optocoupler (6-2) connected to the output end of the circuit, and the output end of the optocoupler (6-2) is connected to the main control module (8). 6. The undervoltage release according to claim 1, characterized in that: the step-down circuit (2) also provides working power for the main control module, switch circuit and relay. 7. The undervoltage release according to claim 1, characterized in that: the main control module (8) is a single-chip microcomputer circuit, which includes: connected with the single-chip microcomputer and suitable for setting and controlling the switch circuit (7 ) BCD dial switch for delayed disconnection time. 8. The undervoltage release according to claim 1, characterized in that: the undervoltage release further comprises a diode (D2), and the anode of the diode (D2) is connected to the step-down circuit ( 2) is connected to the output end, and its cathode is connected to the input end of the electromagnet coil (3). 9. A working method of the undervoltage release as claimed in claim 1, comprising: ① When the undervoltage release is connected to the three-phase power supply, the main control module (8) detects and calculates the effective value of each line voltage of the three-phase power supply through the line voltage detection module (6); ② When the voltage of each line reaches 80% of the rated voltage Ue at the same time, the main control module (8) samples and collects the output voltage of the rectification circuit (1), if the output voltage reaches the specified When the voltage value of the strong start is mentioned, the main control module (8) first controls the relay (4) connected between the output terminal of the rectifier circuit (1) and the current input terminal of the electromagnet coil (3) The open contact is closed, and then the switch circuit (7) connected to the current output terminal of the electromagnet coil (3) is controlled to conduct, so that the electromagnet coil (3) is energized, that is, the armature is attracted; Then, the normally open contact is controlled to be disconnected, that is, only the step-down circuit (2) provides the voltage to maintain the pull-in of the armature; ③ When any line voltage is lower than 50% of the rated voltage Ue, the main control module (8) controls the switching circuit (7) to disconnect, so that the electromagnet coil (3) is de-energized, That is, the armature pops out. 10. The working method of the undervoltage release according to claim 9, further comprising: a method for judging the connection of the electromagnet coil (3), comprising: A: When the line voltage is normal, if the sampling voltage is not equal to the voltage value for maintaining the pull-in of the armature, the main control module (8) controls the switch circuit (7) to disconnect; B: When the sampling voltage returns to the strong start-up voltage value, the main control module (6) generates a control switch circuit (7) conduction to detect whether the electromagnet coil (3) The incoming pulse signal; C: When the sampling voltage drops, it is judged that the electromagnet coil (3) has been connected, and when the sampling voltage reaches the voltage value of the strong start, the main control module (6) controls the The switch circuit (2) is turned on to energize the electromagnet coil (3).