The invention concerns an electromagnetic contactor element which makes it possible to connect or commutate various electrical apparatus and devices, e.g. to switch on, start and control the operation of asynchronous electromotors for which several contactors and a time-lag relay are normally required. The invention generally belongs to class H 01 H, or more precisely to class H01H 03/46 of the International Patent Classification.

The technical problem will be explained on an example of control of an asynchronous electromotor, although this does not exclude the application of the invention in other fields. The technical problem which is successfully solved by present invention is the conception and realization of a contactor element that will successfully replace several contactors, particularly in applications where one element can replace a combination of two or three contactors required according to known solutions, and which form a contactor set; the power and the control part between the contactors have to be linked correctly by way of conductors, as the set may otherwise be damaged or even destroyed.

Known solutions of the given technical problem of e.g. starting and operation of electromotors with powers above 4 kW include a star-delta set consisting of three conventional contactors and a time-lag relay for switching from a star position to a delta position. In order to make the set operate properly it is necessary to link the power contacts of all three contactors in a proper way by conductors, which is a difficult task in sets of higher powers, where conductor cross-sections are greater.

The electromagnetic contactor element in accordance with the invention basically consists of three spatially and functionally installed parts, i.e. a driving part, a contact part and a part which may include an electronic circuit, all three parts being covered by a common cover and fixed by fixation means which, once the cover has been placed, snap into the grooves of the casing, closing in this way the electromagnetic contactor element.

The electromagnetic contactor element in accordance with the invention will be explained in detail by way of example and with reference to the accompanying drawings in which:

Fig. 1 is a side view illustrating an electromagnetic contactor element in accordance with the invention in cross-section;

Fig. 2 illustrates an electromagnetic contactor element in accordance with the invention in A-A cross-section;

Fig. 3 is a plan view illustrating an electromagnetic contactor element in accordance with the invention in B-B cross-section with the support and contacts in position according to embodiment I;

Fig. 4 is a plan view illustrating an electromagnetic contactor element in accordance with the invention in B-B cross-section with the support and contacts in position according to embodiment II; and

Fig. 5 is a plan view illustrating an electromagnetic contactor element in accordance with the invention in partial cross-section.

An electromagnetic contactor element consists of three main parts: A - the driving part, B - the contact part and C - the electronic part; a casing 1

which is closed by a cover 2 which is also fitted with fixation means 3 snapping into the grooves 4 of the casing 1 and causing the closing of the electromagnetic contactor element. The position of the electromagnetic contactor element is indicated by two LEDs 33 installed together with a potentiometer 32 on the cover 2, the red LED indicating the star position and the green LED indicating the delta position.

Two coils 7, 7' are fixed by means of special spring loops 5, 5' in the driving part A to fixed cores 6, 6', the coils having a common moving core 8 over which the force is transmitted through a steel support 9 and a transmission lever 10 to the contact part B. One fixed core 6 is installed in the casing 1, the other fixed core 6' is installed in the cover 2 of the electromagnetic contactor element. The cores 6, 6' are inserted into the grooves of the driving part's casing 11 , and beneath them two leaf springs 12 are placed which absorb the vibrations at making and which are designed so as to make it possible to fix the cores 6, 6' into the casing of the electromagnetic contactor element 1 , 2 in such a way that when the cores 6, 6' are inserted, the springs 12 snap into the grooves 13 of the cores. Between the coil frames 7, T and the fixed cores 6, 6' a coating 14 of e.g. thin rubber is inserted which protects the coil frames 7, T against damage caused by vibrations at making. The common core 8 which floats between the two coils 7, 7', has a groove 15 on both sides, and in this groove lies a steel support 9 across which the motion of the core 8 is transmitted to the lower part of the electromagnetic contactor element to which the transmission lever 10 is fixed, and this transmits the motion from the driving part A to the contact part B.

The contact part B which is composed, in the proposed embodiment, of nine fixed and nine moving contacts, is positioned in the middle of the electromagnetic contactor element in accordance with the invention. The supply contacts 16 - L1, L2, L3 are positioned on the one side, and the discharge contacts U, V, W and 2, X, Y on the other side of the contact part B. The moving contacts 17 are installed on a special moving support 18, which is held in neutral position by four springs 19, so that the moving contacts 17, while at rest, are in a sufficient distance from the fixed contacts 16. The support 18 moves along two grooves 20 in which the springs 19 are installed, which at the same time also hold the moving common core 8 in the driving part A of the electromagnetic contactor element in neutral position via the lever 10 which links the contact part B with the driving part A. The moving contacts 17 are inserted into openings 21 of the support 18 and fixed by springs 22, which when making ensure a sufficiently firm and reliable contact. The central moving contacts 17 perform a double function: they are active in the star position as well as in the delta position and they have contact points 23 on both sides of contact plates 24.

The discharge fixed contacts U, V, W and Z, X, Y are inserted into the casing in such a way that their contact points 25 reach into the middle between the moving contacts 17 far enough to be covered by the contact points of the moving contacts 23. The supply contacts L1 , L2, L3, on the other hand, are built in such a way that each contact has two contact points which also reach into the middle between the moving contacts 17. The neutral point 26 is installed on an insulating support tooth 27 which lies above the supply fixed contacts 16. The outer parts of fixed contacts 16 are

carried out with screws and spring contact plates 28.

A transmission lever 10 is installed at the bottom of the electromagnetic contactor element which transmits the force from the driving part A to the contact part B. At both ends of the lever there are oblong holes 29 with bolts 30 sliding along them. The transmission lever 10 pivots around its axle 31 which is fixed to the lower part of the element in accordance with the invention.

A time-lag relay is installed in the electronic part C which serves for setting the time of switching from the star position a into the delta position b. A potentiometer 32 for setting the time and two LEDs 33 for indicating the position of the electromagnetic contactor element are installed on the cover 2 of the electromagnetic contactor element. The time-lag relay and the coils 7, T in the driving part A are linked with wires which run under the cover 2.

The electromagnetic contactor element is controlled in the same way as any other conventional contactor element with terminals 34 as connectors. Zero conductor N is brought directly to the element, while phase conductor is brought to it indirectly via a breaking push-button. The electromagnetic contactor element is switched on by means of a making push-button by an L'-phase impulse. Terminals 1-2-3 serve as auxiliary contacts.

When the electromagnetic contactor element is switched on via the time-lag relay, the coil 7 engages the moving core 8 whereby the moving support 18 with contacts 17 moves from the neutral position a, the current from the supply contacts L1 , L2, L3 runs over the moving contacts 17 to the

contacts U, V, W and over the winding back to the Z, X, Y contacts of the electromagnetic contactor element, where a neutral point 26 is formed over the moving contacts 35, and the motor starts running at up to 70% of rated rotations. When the starting time runs out, the time-lag relay breaks the coil 7 and makes the coil 7', upon which the moving support 18 with its contacts moves into the position b and the current runs from the supply contacts to the Z, X, Y contacts. The motor is supplied from two sides (delta), it gets its response voltage and thereby the rated rotations, and can thus permanently operate. At breaking, the coil 7' loses its control voltage, the springs 19 equalize the force and thereby push the moving parts into the neutral position, which also causes the breaking of the electromagnetic contactor element.

The contact part B is protected against inter-phase short circuits by phase-field barriers 36. The electromagnetic contactor element can be fixed by screws 37, or it can be mounted on a support bar in a known way.

The proposed embodiment of an electromagnetic contactor element allows yet another application in the control of operation of an electromotor. In known solutions, for the operation of a two-speed electromotor with one winding (Dahlander winding with 2/4 or 4/8 poles) three inter-linked contactors are used which form a set - two contactors are intended for the higher speed and one for the lower speed. The electromagnetic contactor element in accordance with the invention provides the control of such electromotor with the use of a single element. The driving part A is the same as with a star-delta contactor element, whereas part B (as shown in Figure

4) differs both in the number of contacts and in the function. In the electronic part C of this electromagnetic contactor element there is an auxiliary relay over which the coils 7 and 7' in the driving part A are controlled, and through them the higher or lower rotation speed of the electromotor is also defined. The electromagnetic contactor element is controlled as a conventional Dahlander set, i.e. by two push-buttons for the higher and lower speed and by a breaking push-button for switching off the electromagnetic contactor element.

When the electromagnetic contactor element is switched to the lowest speed, the coil 7 engages the moving core 8 in the driving part A, the moving support 18 with contacts moves into position a, the current from the supply fixed contacts L1, L2, L3 runs over the moving contacts 17 to contacts U1, V1 and W1, whereupon the motor starts running at low rotation speed and can thus operate permanently. Upon switching the electromagnetic contactor element to a higher speed, the coil 7' engages the moving support 18 which moves with its contacts into position b, the current runs from the supply contacts back to the contacts U1 , V1 and W1 , where over moving contacts 19 under the supply contacts the neutral point 26 is closed and the motor starts running at higher rotation speed, at which it can also operate permanently. When the contactor is switched off, the coil loses its control voltage, the springs 19 equalize the force and thereby push the moving parts into a neutral position, and the electromagnetic contactor element is switched off.

This description makes it clear that the electromagnetic contactor

element in accordance with the invention significantly simplifies the contactor sets or links known so far in which two or more contactors were needed for the operation of one motor. By a minor change in the contact part it is possible to produce an electromagnetic contactor element for changing the direction of rotation of the electromotor (two contactors are used at present), and an electromagnetic contactor element for controlling a two-speed motor with incorporated two separate windings of 6/4 or 8/6 poles, for which also two conventional contactors are used at present.