Basic technical data on contactors and relays

Thus, E5 means 5 A, Д1 – 10 А, С6 – 600 А. The number that stands in the fifth place indicates the number of normally closed contacts and in the sixth - the amount of normally opened contacts. Lack of normally closed or normally opened contacts is indicated with zero. In case when the number stands at the fifth position and the letter П is in the sixth one, they together mean the number of switching contacts.

The letter, which is in seventh place and points the kind of the given apparatus according the mode of operation, for example: Д – long winding operation; K - short mode of it. In the eighth place a letter can stand, indicating heat mode of relay operation, such as T -temperature relay. For example, ТКЕ52ПК is a switching relay of the intermittent operation, that is designed for a voltage of 30 V and has two switching contacts that can operate at currents that reach 5 A.

Fig. 1.10 presents a general view of the contactor K series of the

retractive type, consisting of an anchor 17, fixed core 14, return springs 15, buffer springs 18, axis of moving contacts 3, moving and 2 fixed 1, 5 contacts, coil 13, a casing 12, panel 7 with the cap 6, washers 4, bus 8, basis 10, screws 9, studs 11and 16.

In case of the power supplying to the coil 13 the magnetic flux is created and it is closed through the fixed core 14, though the air gap, the anchor 17 and through the casing 12. To direct the magnetic flux through the air gap, on the anchor 17 and the stop 14 the brass sleeve is attached. In the process of attraction of the anchor 17 to the core 14, the axis 3 and

the moving contacts 2 begin to move. Fig. 1.10

At this time the return spring 15 starts to shrink. At the collision of moving contacts 2 with the fixed ones 1 and 5 the buffer spring 18 begins to shrink creating pressure between these contacts. The magnetic gap between the anchor and stop is reduced until the moment of their collision. When moving parts are off the voltage contactor returns to its original position under the influence of buffer and return springs.

In these cases, disconnection of contacts is always after the anchor got some speed. This ensures quick opening contacts without sparking.

Fig. 1.11 shows a diagram elektrokinetic contactor series КП: 1 - spring of auxiliary contact; 2 - rod; 3, 6, 10 - springs;

Fig. 1.11

4 - flange; 5 - anchor; 7 - stop; 8.9 - holding and accelerating coil; A - fixed contacts; Б - buses; B - movable contacts.

КП series of switching contactors are designed for remote switching of electric circuits with large current values.

Fig. 1.12 represents the design КП-400Д of contactor: 1 - the screw; 5 - rack; 2, 3 - flanges of the electromagnet; 4 - housing; 6 - cap; A - fixed contacts; Б - buses; B - movable contacts; Г - shunts. As contactors of the series K and KM, they are made for long-term operation mode and are designed for currents of stress 50, 100, 200, 400, 600 A.

Coil of any contactor КП has two windings that are switched on in the certain sequence to the work.

As it is represented on the scheme (fig.1.11), switching on the contactor the current flows through the small-Ohm accelerating coil 9 only. At the end of the movement of the anchor 5 its flange 4 presses the spring contact 1, shunting contacts are opening and consequently with the winding the high-launcher

Fig. 1.12 holding winding 8 switches on.

The scheme of forcing reduces the overall size of contacts due to the large current density in the accelerating coil when it is switched on. Contact device consists of four pairs of power contacts: two pairs of normally opened and two pairs of normally closed are located on two buses. Both movable contact buses are isolated from each other. Due to previous pulling of the return spring 6 (fig.1.11) the necessary contact pressure between normally closed contacts is created. The buffer spring 10 during compression causes pressure on the normally opened contacts. The spring 3 is a damper one. When contactor is switched off it enables the anchor 5 to continue movement after closure of normally closed contacts.

Springs are made from steel, movable and fixed contact buses - from copper with following galvanic tin plate. Power contacts are made from an alloy OK12. Shunt contacts are made silver, and rod - from non-magnetic steel. Cap that protects the contactor from damages is made of aluminum. The plug, which moves the anchor, is made from brass. Contactors of other types are constructed of the same materials.

Contactors КМ-100Д, КМ-200Д, КМ-400Д, КМ-600Д have much similar features with contactors of series КП because they are made with forcing, with magnetic path of retractive type and with flat end of a stop. These contactors are working only to switch on, so they have only one moving bus with two contacts and no damper spring. In double-coils series KM ф single-coil contactors are applied, but they work only in short-term modes. Relays and contactors of valve type differ from each other only by the capacity of switched circuits.

Contactors in aircraft three-phase alternating current circuits are divided into two parts: three-phase closing switching and switching. Fig. 1.13 represents principal circuit diagram for three-phase closing switch contactor 1 - alternating winding; 2 - holding winding; К – mechanic contacts.

Fig.1.13

A peculiarity of the three-phase contactors is the contact system separation into three separate contact groups placed in separate cells. These contact chambers must be electrically isolated from each other.