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Working principle and testing method of AC contactor

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AC contactor is a kind of inductive control switch. It is a kind of automatic household appliances with the help of electromagnetic induction force. It is used to connect or disconnect the power supply circuit of motor or other power consumption machinery and equipment. It is suitable for long-distance connecting or disconnecting the main power supply circuit of AC / DC power supply or large space control circuit.

Principle and inspection method of AC contactor

AC contactor is divided into AC contactor (working voltage AC) and DC contactor (working voltage DC). It is used in power engineering, distribution equipment and power consumption places. In theory, AC contactor refers to the household appliances that use the coil to pass through the current to cause the electromagnetic field in the industrial production of electricity, and make the contact close, so as to control the load.

AC contactor consists of four parts

Principle and inspection method of AC contactor

(1) The software of electromagnetic induction system includes attracting coil, moving transformer core and Kuqa transformer core;

(2) Contact system software consists of three groups of main contacts and one to two groups of on-off and normally closed auxiliary contacts. It is connected with the iron core of dynamic transformer and moves with each other. The main contact is generally on-off contact, while the auxiliary contact often has a pair of on-off or normally closed contact;

(3) For arc extinguishing equipment, generally large volume AC contactor is equipped with arc extinguishing equipment, which is convenient to quickly disconnect the electric arc and avoid burning the main contact;

(4) Insulation shell and accessories, all kinds of springs, transmission mechanism, short circuit fault ring, wiring head, etc.

Principle and inspection method of AC contactor

The principle of AC contactor is: when the coil of AC contactor is connected with power supply, the coil current will cause electromagnetic field, which makes the static transformer iron core cause electromagnetic induction adsorption force to attract the dynamic transformer iron core, and push the point posture of AC contactor. The normally closed contact is broken and the normally open contact is closed. They are linked. When the coil turns off the power supply, the electromagnetic induction adsorption force dissipates, and the streamline coil is released under the effect of spring yellow, so that the contact is restored, the normally open contact is broken, and the normally closed contact is closed.

Principle and inspection method of AC contactor

The mark no indicates on and off. Normally open contact is broken in general, that is, the coil is not powered. NC indicates that it is normally closed. Normally closed contacts are normally open, that is, closed when the coil is not powered on.

There is a coil mark in the middle of A1 and A2 terminal blocks, which means the following meanings:

M5 coil is communication AC 220 V 50 Hz, M7 coil is communication AC 220 V 50 / 60 Hz; Q5 coil is communication AC 380v50 Hz, Q7 coil is communication AC 380v50 / 60 Hz. AC contactors generally cooperate with each other for auxiliary contact application. Model selection of AC contactor Rated current of main contact 1 The rated current of the main contact exceeds the rated current of the load. 2. Rated voltage of main contact The rated voltage of the main contact exceeds the rated voltage of the load. 3. Rated current of coil The rated current of the coil is selected according to the working voltage of the control circuit. Coil resolution Set the compass digital multimeter to "R × 100", zero or set the digital multimeter to 2m. Principle and inspection method of AC contactor 2. Touch coil screw A1 and A2 according to DC ammeter, if it is zero, it indicates short circuit fault; if it is infinite, it indicates lead. The distinguishing way of contact 1. Set the compass digital multimeter to "R × 100", zero or set the digital multimeter to 2m. 2. Use the two DC ammeters of the digital multimeter to contact the terminals of the two contacts at random. If the needle does not move, it may be the normally open contact; if not, it may be the normally closed contact. Principle and inspection method of AC contactor 3.If the needle doesn't move, when the function key of mechanical equipment is pressed and held, the needle will turn to zero, then it is a normally open contact pair; when the normally closed contact pair is pressed and held, the needle will return to infinity from zero.

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