Aikacewa da Jimin Kalmomin AC | Tushen Littattafan Inganci a Kan Jimin Kalmomi Da Zaka Yi A Farko

1 Bayanin Muhimman Kompontantuka na AC Contactor

AC contactor shi ne fayilolin kimiyya mai karfi da ake amfani da ita don zaba da gudanar da tushen AC masu zaman kansu da tushen kontrol. Ana iya yi aiki da ita daga lokacin da yake da tsari zuwa lokacin da yake da hankali. Ana iya haɗa aikinsu da aiki da ita, inganci da kuma lalacewar abubuwan da suka rage, aiki da muhimmanci, damar daidai, da kuma lafiya da ba sa shiga. A cikin tushen kontrol na makaranta, ana amfani da AC contactors domin kontrola mutane da kuma abubuwan da suka rage.

Muhimman kompontantukan na AC contactor sun hada da kimiyyar tushen magana, tushen magana, da kuma tushen mafi girgirar kimiyya, baka daya. Ana iya haɗa aikinsu da tushen magana, iron core mai yawa, coil, iron core mai rike, da kuma tushen magana mai biyan.

1.1 Kimiyyar Tushen Magana

Kimiyyar tushen magana na AC contactor ya haɗa da coil, moving iron core, static iron core, da kuma short-circuit ring. Idan coil ta shiga ko ta rage, za a yi aiki a taka da tafiyar pulling-in ko releasing, wanda zai taimaka da tushen magana mai yawa da tushen magana mai rike suka ci gaba ko ci gaba, don haka za a iya bayyana tushen magana.

Don jin dadin eddy current da hysteresis, iron core da armature na AC contactor suna da E-shaped silicon steel sheets da ake samun aiki a matsayin tashar tushen magana. Don haɗa aiki a kan tashar tushen magana, coil an samu a cikin insulating frame, da karamin hanyar da ake da a taka da iron core. Iron core na E-shape na da air gap na 0.1 - 0.2 mm a kan end face na middle cylinder don jin dadin residual magnetic field da kuma jin dadin armature jamming.

A lokacin da AC contactor ya shiga aiki, alternating current a cikin coil ya shiga akiyar magnetic field a cikin iron core, wanda ya taimaka da armature suka shiga da noise. Ana iya haɗa aiki a kan iron core da armature, da kuma short-circuit ring da ake samu a cikin groove. Ba a yi short-circuit ring, idan alternating current ta shiga winding, za a samu magnetic fluxes Φ₁ da Φ₂ da ake da hanyoyi, wanda zai taimaka da akwai attractive force daga iron core zuwa armature, da kuma jin dadin vibration da noise.

1.2 Tushen Magana

An samu tushen AC contactor da tare da point contact type, line contact type, da kuma surface contact type, kamar da ake bayyarta a cikin wannan rubutu. Daga haka, ana iya haɗa aiki a kan bridge contacts da finger contacts. Bridge contacts sun hada da point-contact bridge type da surface-contact bridge type, wadanda suka da muhimmanci a cikin yanayi da tushen magana. Finger contacts suna da line contact mode, wadanda suka da muhimmanci a cikin yanayi da tushen magana mai yawa. Daga haka, ana iya haɗa aiki a kan main contacts da auxiliary contacts. Main contacts suka da muhimmanci a cikin tushen magana mai yawa, da kuma 3 pairs of normally open contacts. Auxiliary contacts suka da muhimmanci a cikin tushen kontrol mai biyan, da kuma 2 pairs of normally open contacts da 2 pairs of normally closed contacts.

1.3 Tushen Mafi Girgirar Kimiyya

Idan tushen magana mai yawa ko tushen magana mai yawa, za a samu arcs lokacin da AC contactors suka ci gaba, wanda zai taimaka da tushen magana suka rage, da kuma tushen magana suka rage, da kuma tushen magana suka rage, da kuma tushen magana suka rage. Saboda hakan, duk contactors da suka da capacity mai yawa 10 A, ana bukatar tushen mafi girgirar kimiyya. Ana iya haɗa aiki a kan double-break electric force arc extinguishing, longitudinal slot arc extinguishing, da kuma grid arc extinguishing.

Double-break electric force arc-extinguishing device ya haɗa da arcs da ake samu biyu, da kuma ake samu electric force da ake samu a cikin contact circuit itself, wanda zai taimaka da heat dissipation da cooling da kuma taimaka da arcs suka rage. Longitudinal slot arc-extinguishing device an samu a cikin arc-resistant clay, asbestos cement, da kuma abubuwan da ake samu a cikin inner side, wanda zai taimaka da contact area da arcs da wall of the arc-extinguishing chamber suka rage, da kuma taimaka da arcs suka rage. Idan tushen magana suka ci gaba, arcs an samu a cikin slots through an external magnetic field or electric force, da kuma heat energy an samu a cikin wall of the arc-extinguishing chamber, don haka arcs suka rage saki.

Daga haka, an samu sabon grid arc extinguisher structure. Metal grid an samu a cikin herringbone copper-plated or galvanized iron sheets da ake samu a cikin arc-extinguishing cover. Arcs da ake samu a cikin contact breaking an samu strong magnetic field, da kuma magnetic resistance an samu electric field intensity a cikin area da ke da uneven, wanda zai taimaka da arcs an samu a cikin gaps of the grid to form short arcs. Each grid an samu as an electrode, da kuma an samu entire arc voltage drop into several sections, da kuma arc voltage between each section an samu less than the arc ignition voltage. Da kuma, grid an samu heat to eliminate the arc quickly, taimaka da arcs suka rage [3-5].

1.4 Tushen Biyan

Tushen biyan na AC contactor sun hada da reaction spring, buffer spring, contact pressure spring, transmission mechanism, base, baka daya. Reaction spring an taimaka da armature suka rage a lokacin da power failure, wanda zai taimaka da tushen magana suka rage a cikin harkokin da suka rage. Buffer spring an taimaka da impact force suka rage. Contact pressure spring an taimaka da contact pressure suka rage da kuma taimaka da contact resistance suka rage. Operating contacts an taimaka da armature or reaction spring suka rage, don haka za a iya bayyana tushen magana suka rage.

2 Amfani da AC Contactors Da Hukuma

2.1 Principles of Selection na AC Contactors

Rated voltage na main contacts ba zai iya da rated voltage na control circuit. Rated current na main contacts ya kamata aiki da load requirements: for resistive loads, it should be equal to the rated current; for motor loads, it should be slightly greater than the rated current. Voltage na attraction coil an samu according to the complexity of the control circuit: 380 V or 220 V can be selected for simple circuits, and 36 V or 110 V for complex circuits. The number and type of contacts must meet the basic standards of the control circuit.

2.2 Installation and Maintenance na AC Contactors

For the pre-installation inspection, it is necessary to confirm whether the technical data of the contactor (such as rated voltage, current, operating frequency, etc.) comply with the standards, check whether the appearance is damaged and the movement is flexible, and measure the DC resistance value and insulation resistance value of the coil. The installation position should be vertical, with an inclination not exceeding 5°, and the side with heat dissipation holes should face the vertical direction. During installation and wiring, prevent parts such as screws, washers, and terminals from falling, which may cause the AC contactor to be stuck or short-circuited.

After installation, it is necessary to check whether the wiring is correct. Without energizing the main contacts, energize and de-energize the contactor several times to check the movement of the main contacts and whether there is noise after the iron core is pulled in. It can be put into use only if there is no error. It is not allowed to connect the AC contactor to a DC power supply, otherwise the coil will be burned out.

3 Common Faults and Maintenance Methods na AC Contactors

3.1 Main Contact Faults

3.1.1 Severe Sparking at the Moment of Connection and Disconnection of Moving and Static Main Contacts

When the load is working normally, sparking occurs at the moment the contacts are connected and disconnected. The contact surface forms irregular small pits due to the high temperature of the arc, resulting in reduced contact area, increased current, and severe sparking. To repair the damaged contacts, it is necessary to check the degree of damage on the contact surface; the contact can be repaired only if its thickness is more than 2/3 of the original thickness. When repairing the contacts, first place fine sandpaper on a horizontal surface, then grind the damaged contacts flat on the sandpaper, check the repair situation until all damaged points are ground off, and finally deal with the burrs.

3.1.2 Melting, Burning and Adhesion of Moving and Static Main Contacts

The main causes of melting, burning and adhesion of moving and static main contacts include short circuit of the load, short circuit of the main circuit, or reduction of load impedance. Among them, the simultaneous occurrence of short circuit and main circuit short circuit is the key factor. Due to work needs, the operating frequency of the AC contactor ranges from low to high; during the frequent connection and disconnection of the contacts, the surface temperature rises, and under the action of the arc, the moving and static main contacts will eventually melt, burn and adhere.

There are generally two treatment methods: first, replace the AC contactor with one with a higher voltage and current rating; second, repair the AC contactor: replace the contacts with the same specification, clean the carbon deposits around the moving and static contacts, etc., and connect Resistor-Capacitance (RC) arc-extinguishing devices in parallel with each of the 3 pairs of main contacts.

3.2 Auxiliary Contact Faults

3.2.1 Excessively High Contact Resistance of Moving and Static Auxiliary Contacts

Excessively high contact resistance of moving and static auxiliary contacts will lead to an increase in the loop impedance of the control circuit and a decrease in voltage. There are two main reasons for this phenomenon: first, a large amount of oil stains and dust are deposited on the contacts; second, an oxide layer is formed on the contact surface. Based on the under-voltage protection mechanism of the AC contactor, when the voltage across the AC contactor coil is lower than 85% of the rated voltage, the control circuit will stop working. The solution is to take out the contacts, wipe them dry with clean gauze, and then gently treat the contact surface with fine sandpaper.

3.2.2 Severe Sparking at the Moment of Connection and Disconnection of Moving and Static Auxiliary Contacts

The main reasons for this fault may be that the controlled circuit has experienced a short circuit, or the impedance value of the energy-consuming components in the control circuit has decreased, etc.

3.3 Coil Faults

3.3.1 Coil Open Circuit

An open circuit of the AC contactor coil will cause the control circuit to fail to work. This phenomenon is relatively rare, and it is generally caused by quality problems of the contactor or improper installation during assembly.

3.3.2 Coil Short Circuit

A short circuit of the AC contactor coil will cause the fuse of the short-circuit protection in the control circuit to blow. A common situation of coil short circuit is that the AC voltage applied across the coil is not 0.85-1.05 times the rated voltage; long-term operation of the coil under low or high voltage may cause a short circuit. A damaged AC contactor coil must be replaced; when replacing the coil, attention should be paid to the coil size, rated voltage, and the specification of the AC contactor.

3.4 Faults of Moving and Static Iron Core Contact Surfaces

3.4.1 Adhesion of Moving and Static Iron Core Contact Surfaces

The main reason for this fault is the presence of oil stains on the contact surfaces of the moving and static iron cores. After pressing the start button, the motor runs normally, but when pressing the stop button, the AC contactor coil loses power, the contacts do not return to their original state, and the motor continues to run. After the hand leaves the stop button, the coil remains energized, and the motor continues to run. The treatment method is to clean the contact surfaces of the moving and static iron cores.

3.4.2 Loud Noise from the Iron Core

The main reasons for loud noise from the iron core are the breakage of the short-circuit ring, or a large amount of rust on the contact surfaces of the moving and static iron cores. For the case of a large amount of rust, fine sandpaper can be used to treat the contact surface. If the short-circuit ring is damaged, the iron core is generally replaced to repair the fault.

4 Conclusion

The proper use, fault diagnosis and maintenance skills of AC contactors are crucial to the stable operation of electrical control systems. In order to improve the service efficiency of AC contactors and extend their service life, common faults should be repaired in a timely manner to reduce the failure rate during production.