Magnetic contactors: device and assignment

The contactor is called the electromagnetic device of remote action intended for frequent inclusions and shutdowns under loading of the electric power circuit.

Контактор переменного тока типа КТ, трехполюсный, с дугогашением.

Figure 1: 1 - the yoke with the core, 2 - the short-circuited round, 3 - the anchor, 4 - the emphasis; 5 - the involving coil, 6 - the holder of the anchor, 7 - the shaft insulating, 8 - the disconnecting interlock contacts, 9 - the closing interlock contacts, 10 - mobile main contact; 11 - motionless main contact; 12 - arc-suppressing cameras.

Except inclusion and shutdown the contactor carries out  also zero protection of electric motors, i.e. disconnects him at disappearance of tension in the power line, and at repeated giving of tension itself does not join.

In remote control of electric motors the contactor finds the broadest application.

By the principle of action the contactor represents the vyklyuchayotel with the contacts managed by the electromagnet. The main parts of the contactor are the main contacts, the magnetic sisyotema, the involving coil, the arc-suppressing device, interlock contacts.

Let's trace work of the contactor on the example of action of the alternating-current contactor like KT produced by the domestic industry. The device of this contactor is represented in fig. 1.

 Электрическая схема включения контактора с управлением при помощи двух штифтовой кнопки.

The fig. 2 Circuitry of Inclusion of the Contactor with management by means of two the bayonet button.

And the unrolled circuitry of the vklyuyocheniye of the contactor together with the two-bayonet button of management is given in fig. 2. If to press the start-up button, then the electric circuit is formed: current goes from the phase L to the involving coil K, further through the disconnecting contacts of the feet button, via the start-up button (closed when pressing) and to the phase L3. Owing to the current flow through the involving coil 5 the motionless part of magnetic system 1 (the yoke with the core in fig. 2) is magnetized and attracts the mobile part of magnetic system (the anchor 3). The anchor, being fastened to the contactor's shaft, turns it and closes podyovizhny contact 10 with motionless 11 (in fig. 2 contacts of group of companies). Besides, also closing interlock contacts 9 will work, and interlock contacts 8 are disconnected. After inclusion of the contactor the start-up button can be released, and the elektriyochesky chain is not broken off by it as current goes on the zamkyonuty chain now: the phase L1 — the involving coil K — the feet button — the BQ interlock contact (which will close now) and the phase L3. At the nayozhatiya of the feet button the control circuit is disconnected, and the anchor shaft under the influence of the weight disappears, breaking off the power chain.

At reduction of tension below the certain size (it dayotsya in catalogs percentage of rated voltage) the konyotaktor is automatically disconnected as the weight of mobile parts of the contactor exceeds force of interaction of mobile and nepodyovizhny parts of magnetic system at the reduced tension. If tension is given, and the start-up button is not pressed, then the contactor does not work as the chain of the involving razomkyonut coil. Zero protection of the electric motor is provided to these.

Contactors are produced for work in chains constant and alternating-current.

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