CN100490043C - Permanent magnet non-arching AC contactor - Google Patents

Abstract

A permanent magnet arc-free AC contactor belongs to the field of low-voltage electrical appliances. The contactor includes an upper end cover, a thyristor and a control part, a permanent magnet, a moving contact, a static contact, a main contact terminal, a movable bracket, a conductive rod, Armature, iron core, coil, shell and base; the control part of the thyristor and the control part is composed of a control unit, a switching element, an energy storage element and an IGBT element, and the control unit is connected with the thyristor, switching element, storage The energy element is connected to the IGBT element; one end of the IGBT element is connected to any phase of the three-phase voltage through a coil, and the other end is connected to the other phase of the three-phase voltage; both ends of the switching element and the energy storage element are connected to the coil; the contactor A pair of anti-parallel unidirectional thyristors are connected in parallel at both ends of each contact, and then connected to the power supply and the load respectively. The invention has the advantages of simple structure, no change of the original contactor dimensions, easy process realization, noiseless operation, arc-free on-off, etc., and the power saving rate reaches more than 90%, which greatly improves the electrical life of the contactor.

Description

Permanent magnet arcless AC contactor

technical field

The invention belongs to the field of low-voltage electrical appliances, in particular to a permanent magnet arcless AC contactor.

Background technique

When the traditional AC contactor is working, an arc will be generated during the pull-in and break-off process, and the coil must be energized to keep the contactor in the pull-in state after the contactor is closed. When the circuit is turned on and off, there are shortcomings such as strong arcs on the main contacts, which not only causes a lot of waste of electric energy, pollutes the surrounding environment, but also greatly reduces the electrical life of the contactor.

Over the years, electrical workers have carried out a lot of work to improve various performances of contactors, such as energy saving, some use AC pull-in, DC hold; some use high-voltage DC pull-in, low-voltage DC hold, etc., although they have energy-saving functions , but the coil is still energized, it’s just a low-voltage direct current, and the coil still has current, so the energy-saving goal cannot be fully achieved.

In addition, when the arc is generated in the contactor on-off circuit, many researchers have adopted a variety of methods to extinguish the arc, such as increasing the magnetic field to blow the arc, and using a metal grid arc extinguishing chamber. Figure 1 shows a schematic cross-sectional view of the existing AC contactor structure, which includes arc extinguishing cover, arc extinguishing grid, moving contact, static contact, main contact terminal, movable support, conductive rod, armature, iron core, coil , shell and base.

None of the above-mentioned methods can fundamentally eliminate the arc, but only limit and help to extinguish the arc. Although the non-contact switches currently on the market are arc-free products, they are expensive, and because there are no mechanical contacts, they have high conduction loss, poor overload capacity, and are bulky.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention provides a permanent magnet arcless AC contactor.

The structure of the contactor is shown in Figure 2, including the upper end cover, the thyristor and the control part, the moving contact, the static contact, the main contact terminal, the movable support, the conductive rod, the armature, the iron core, the coil, the permanent magnet, The shell and the base, the shell 10 is covered on the base and 11 to form a cavity, in which the iron core 8 is fixed on the center of the base 11, the iron core 8 is concave, and the bottom of the iron core has a square groove for placing the permanent magnet 13. The two protruding columns are surrounded by coils 9, the tops of the two columns form a closed magnetic path with the armature 7, the armature 7 is fixedly connected with the movable bracket 6, and the main contact terminal 5 forms a mechanical connection with the static contact 4 through the conductive rod 14. Connection, there are two breakpoints between the moving and static contacts, the thyristor and the control part 12 are installed in the upper end cover 15 to form a complete contactor.

A permanent magnet is placed in the center of the bottom of the contactor iron core 8 of the present invention, and its structure is shown in FIG. 3 .

In the present invention, the thyristor and the control part replace the arc extinguishing device of the existing contactor, which includes the thyristor part and the control part, and the control part is composed of a control unit, a switching element, an energy storage element and an IGBT element. The control unit is connected to the thyristor part, switching element, energy storage element and IGBT element; one end of the IGBT element is connected to any phase of the three-phase voltage through a coil, and the other end is connected to the other phase of the three-phase voltage; the switching element Both ends of the energy storage element are connected to the coil; each contact of the contactor is connected in parallel with a pair of anti-parallel unidirectional thyristors, and then respectively connected to the power supply and the load, as shown in Figure 4.

When the contactor of the present invention is working normally, first press the start button SA1, and the control part starts to work, because the inherent pull-in time of the contactor is 20ms, and the control part makes the thyristor conduct before the contactor contact in 10ms, realizing Arc-free connection; at the same time, the control part makes the IGBT element connected in series with the contactor coil conduct for 30ms at 10ms, so that the contactor is turned off after being closed, and there is no more current in the coil. At this time, the contactor is maintained by the improved design The magnetic flux generated by the permanent magnet in the iron core is realized, so that arc-free connection and power-saving and noise-free operation are realized; when the stop button SA2 is pressed and the contactor coil is powered off, the inherent release time of the contactor is 15ms , the switching element first switches the coil of the contactor to the energy storage element, and uses the energy of the energy storage element to reversely demagnetize the permanent magnet in the iron core, so that the contactor starts to release, and at the same time provides the trigger voltage for the thyristor to continue 20ms, so that when the contactor contact is about to open for nearly 15ms, due to the sharp increase in contact resistance, when the voltage drop across the contact increases to about 8V (less than the arc voltage), since the trigger signal always exists, the thyristor is activated by The non-working state short-circuited by the contact turns into a conductive state. This conversion process is extremely short (microseconds). Before the contact is opened, the current flowing through the contact has been transferred to the thyristor, so that the contact is almost It is opened in the case of no-load breaking, that is, to achieve no-arc breaking, until the thyristor is cut off due to the disappearance of the trigger signal at 20ms.

The invention utilizes the cut-off of the thyristor to realize the disconnection of the circuit, thereby realizing the function of arc-free on-off, and at the same time, the conduction of the circuit is carried by the mechanical contact, which overcomes the problems of high conduction loss and poor overload capacity of the non-contact switch. shortcoming. In addition, the contactor coil of the present invention has a large current flowing only at the moment of contactor pull-in and release (no more than 30ms), to ensure the pull-in (excitation) and release (demagnetization) of the contactor, and the contactor is pulled in until released Before, there is no current in the coil. Therefore, the number of turns and the wire diameter of the coil after the improved design have greatly changed, saving a lot of copper. The invention also has the advantages of simple structure, no change of the original contactor dimensions, easy process realization, noiseless operation, etc., and the power saving rate reaches more than 90%, which greatly improves the electrical life of the contactor.

Description of drawings

Figure 1 is a schematic cross-sectional view of an existing AC contactor structure;

Fig. 2 is a schematic cross-sectional view of the contactor structure of the present invention;

Fig. 3 is the magnetic system structural representation that contactor of the present invention is equipped with permanent magnet;

Fig. 4 is a schematic block diagram of the circuit of the present invention;

Fig. 5 is the schematic circuit diagram of the embodiment of the present invention,

(a) is the schematic diagram of the control part circuit in the specific embodiment,

(b) is a schematic diagram of the thyristor part of the circuit in the specific embodiment.

In the figure 1——arc extinguishing cover, 2—arc extinguishing grid, 3—moving contact, 4—static contact, 5—main contact terminal, 6—movable bracket, 7—armature, 8—iron core, 9—coil, 10—shell, 11—base, 12—silicon controlled rectifier and control part, 13—permanent magnet, 14—conductive rod, 15—upper end cover, 16 --Control section.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

Figure 2 is a schematic cross-sectional view of the structure of this embodiment, which includes an upper end cover, a thyristor and a control part, a moving contact, a static contact, a main contact terminal, a movable support, a conductive rod, an armature, an iron core, a coil, The permanent magnet, the shell and the base, wherein the thyristor and the control module replace the arc extinguishing part of the existing contactor, and a permanent magnet is added at the bottom of the iron core. The casing 10 is covered on the base 11 to form a cavity. In the cavity, the iron core 8 is fixed on the center of the base 11. The iron core 8 is concave, and the bottom of the iron core has a square groove for placing the permanent magnet 13. Coils 9 surround the two uprights, the tops of the two uprights form a closed magnetic path with the armature 7, the armature 7 is fixedly connected with the movable bracket 6, and the main contact terminal 5 forms a mechanical connection with the static contact 4 through the conductive rod 14. There are two breakpoints between the contacts, and the thyristor and the control part 12 are installed in the upper end cover 15 to form a complete contactor.

Fig. 3 is a schematic structural diagram of the magnetic system in this embodiment.

Fig. 5 (a) shows the schematic diagram of the circuit of the control module of this embodiment, two relays in the figure, the first relay KA1 and the second relay KA2 realize the switching function, and the circuit formed by the third capacitor C3 and the sixth diode D6 Realize the energy storage function, IGBT, YMDZ realize the IGBT function, the first voltage comparator U1A, the second voltage comparator U1B and their peripheral circuits realize the control function, in which the coil of the first relay KA1 is directly connected with the 12V power supply, a pair of normal The open contacts are respectively connected to the 380V pulsating DC power supply and the collector of the IGBT, while a pair of normally closed contacts are connected to the contactor coil; one end of the coil of the second relay KA2 is connected to the 12V power supply, and the other end is connected to the collector of the transistor Q1 The first end of the first normally open contact is connected to the first end of the second normally open contact through the third capacitor _C3 and the sixth diode D6, and the second end of the first normally open contact is connected to the The second end of the second normally open contact is connected to the ground; the output end of the first voltage comparator UIA is connected to the base of the IGBT through the eighth resistor R8, and the negative end of the two input ends is respectively connected to the first The six resistors R6 are connected to one end of the seventh resistor R7, and the positive ends of the two input terminals are respectively connected to one end of the fifth resistor _R5 , the anode of the fifth diode _D5 , and the negative electrode of the second capacitor _C2 ; The output terminal of the second voltage comparator UIB is connected to the base of the transistor Q1 through the fourth resistor R4, and the output terminal of the second voltage comparator UIB is also connected to the second capacitor C2 through the third diode D3 at the same time, and the two input terminals The positive end of the first resistor _R1 is connected to one end of the first resistor R1, the positive electrode of the first capacitor _C1 and the anode of the second diode _D2 ; the base of the IGBT is connected to the first voltage comparator UIA through the eighth resistor R8 At the output terminal, the collector is connected to the 380V pulsating DC power supply through the sixth diode D6, the emitter is connected to the ground, and a varistor YMDZ is connected in parallel between the emitter and the collector; the first diode is connected between the 12V power supply and the ground Tube D1, the control part of the circuit is connected with the thyristor part of the circuit in Figure 5 (b) through the connection points (a', b').

Figure 5(b) shows the schematic diagram of the thyristor part of the circuit in this embodiment, using a conventional thyristor control circuit. In the figure, a pair of anti-parallel thyristor SCRs are connected in parallel at both ends of each phase contact KM , when the contactor coil is energized, the inherent pull-in time of the contactor is about 20ms, and the trigger circuit in the figure makes three pairs of anti-parallel thyristors turn on at 10ms, so that the thyristors are already ahead of the touch of the contactor. The head connects the circuit, and when the contact is closed in 20ms, the contact only short-circuits the silicon controlled rectifier, because the voltage drop of the silicon controlled rectifier is not enough to generate an arc, so the arc-free connection function is realized. When the coil is powered off, the inherent release time of the contactor is about 15ms, and the thyristor trigger circuit keeps the triggering state until 20ms due to the current released by the energy storage capacitor C1, so that when the contactor is nearly 15ms When the contact is about to open, due to the sharp increase of the contact resistance, when the voltage drop across the contact increases to about 8V (less than the arc voltage), since the trigger signal always exists, the thyristor is short-circuited by the contact. This transition process is extremely short (microsecond level). Before the contact is opened, the current flowing through the contact has been transferred to the thyristor, so that the contact is almost in the case of no-load breaking. Open until 20ms when the thyristor is cut off due to the disappearance of the trigger signal, so that the circuit can realize arc-free breaking.

Claims (2)

1. permanent magnetism Arcless AC Contactor, comprise upper end cover, moving contact, fixed contact, main contact terminal, travel(l)ing rest, conducting rod, armature, iron core, coil, shell and base, it is characterized in that also comprising controllable silicon and control section, permanent magnet, iron core becomes matrix, the iron core bottom has square groove, place permanent magnet, controllable silicon and control section are installed in the upper end cover; Control section is made up of control unit, switching device, energy-storage travelling wave tube and IGBT element in controllable silicon and the control section, and control unit links to each other with controllable silicon part, switching device, energy-storage travelling wave tube and IGBT element respectively; IGBT element one end is connected to any phase in the three-phase voltage by coil, and another links to each other the other end and three-phase voltage; The two ends of switching device and energy-storage travelling wave tube all link to each other with coil; Each two ends, contact of the contactor of being made up of moving contact and fixed contact a pair of reciprocal one-way SCR respectively in parallel is connected with load with power supply respectively again.

2. according to the described a kind of permanent magnetism Arcless AC Contactor of claim 1, it is characterized in that the first relay (KA in the control section circuit ₁) coil directly link to each other with DC power supply, its a pair of normally opened contact links to each other with the collector electrode of Voltage pulsating direct-current supply and IGBT respectively, and two moving contacts of a pair of normally-closed contact link to each other with two end points of contactor coil; Second relay (the KA ₂) coil one end link to each other the other end and triode (Q with DC power supply ₁) collector electrode link to each other, first end of its first normally opened contact is by the 3rd electric capacity (C ₃) and the 6th diode (D ₆) link to each other with first end of second normally opened contact, second end of first normally opened contact links to each other with AC power, and second end of second normally opened contact links to each other with ground; The output of first voltage comparator (UIA) is by the 8th resistance (R ₈) link to each other negative terminal in its input and the 6th resistance (R with the base stage of IGBT ₆) and the 7th resistance (R ₇) an end link to each other, the anode in the input respectively with the 5th resistance (R ₅) an end, the 5th diode (D ₅) the anode and the second electric capacity (C ₂) negative pole link to each other; The output of second voltage comparator (UIB) is by the 4th resistance (R ₄) and triode (Q ₁) base stage link to each other the anode in its input and the first resistance (R ₁) end, the first electric capacity (C ₁) the positive pole and the second diode (D ₂) anode link to each other the negative terminal in the input and the second resistance (R ₂) and the 3rd resistance (R ₃) an end link to each other, the collector electrode of IGBT is by the 6th diode (D ₆) link to each other with Voltage pulsating direct-current supply, emitter links to each other with ground, a piezo-resistance in parallel between emitter and the collector electrode; Be connected to the first diode (D between DC power supply and the ground ₁), control section circuit and controllable silicon partial circuit link to each other by tie point (a ', b ').

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