DE1515603A1 - Switch arrangement for switching an AC-powered consumer on and off - Google Patents

Description

PATENT LAWYERS DIPL-ING, CURT WALLACH DIPL.-ING. GÜNTHER KOCH 1515603 DR. TINO HAIBACH

8 Munich 2, December 6, 196

OUR MARK: 10 Il6 - W / Κβ

Switch arrangement for switching on and off an AC powered Consumer

The invention relates to a switch arrangement for switching on and off an AC-powered consumer with semiconductor valves connected in parallel to a mechanical main contact, which are switched by an auxiliary contact activated depending on the main contact.

There are already completely contactless semiconductor switch assemblies known in which there is no wear. You will instead the conventional switch used when it is heavily used and operated very frequently.

However, in certain cases of application, especially when tempering of squirrel-cage motors, extremely strong inrush currents occur when starting, which is the case when dimensioning of the semiconductor must be taken into account. Because of their low heat capacity, these semiconductors can only overload tolerated for a very short time. One is therefore because of the operational safety too strong oversizing, which reflected in high prices, forced.

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Therefore, in such a case, purely contactless switching is dispensed with and semiconductors and mechanical contacts are used common switch. Through the semiconductors, the arcs and the mechanical stresses on the mechanical Contacts are avoided and vice versa, the mechanics see contacts in the semiconductors avoid thermal voltage surges. This combination is quite inexpensive while eliminating the disadvantages of the other components.

However, the devices proposed so far require for one Effective way of working at the same time, complicated and very precise control means in order to carry out the synchronizations that are particularly necessary when opening to ensure.

The object of the invention is to simplify the control circuit while avoiding forced mechanical synchronizations using an auxiliary contact in the control circuit of the valves, which is operated with the main mechanical contacts.

In the case of a switch arrangement for switching an AC-powered consumer on and off, this task becomes one mechanical main contact semiconductor valves connected in parallel, which are actuated by a depending on the main contact Auxiliary contact are switched, according to the invention achieved in that the semiconductor valves anti-parallel connected semiconductors are, of which at least one is controllable and with its control electrode with the help of the mechanical auxiliary contact when the main contact is closed, it is switched to open-air operation and after the main contact is opened, it is switched to blocking operation, and that the actuation circuit for the main contact is parallel to the consumer.

When switching on, the valve is first switched to its conductive state and briefly takes over the current until the mechanical main contact is closed, which is against

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Effects of switching operations is protected. When switching off, conversely, the valve takes over the current first while the main contact opens, only then does the valve also block after its control voltage has been switched off.

Semiconductor arrangements which conduct in two directions are preferably used as valves, for example in the form of two parallel and oppositely connected valves, at least one of which is controlled and which are arranged in such a way that that a current flow is prevented as long as no valve has been made conductive. Because the auxiliary contact is in the control circuit the valve is firmly connected to the actuation mechanism of the mechanical contacts and itself again by an electromagnet is controlled depending on the consumer, the desired switching sequence is inevitably achieved.

In a further embodiment of the invention, the mutual Dependency of the mechanical contacts and the controlled semiconductor valves through an electrical interlock of the Control circuits for the contacts and the semiconductors ensured.

The invention is explained below on the basis of exemplary embodiments. Show it:

1 shows the basic circuit of the invention;

2 shows an embodiment of the switch arrangement according to the invention with two controlled valves in a single-phase system

3 shows a modification of the circuit for the control electrodes the valves used in Fig. 2;

4 shows a modified single-phase circuit for single-phase power with various types of valves;

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Pig. 5 the switch arrangement according to the invention in a three-phase system with star connection of the consumer}

Pig. 6 an example of the electrical interlocking of the control circuits of the mechanical contacts and the controlled ones Valves in one of the phases of the device according to FIG. 5.

The one shown in Fig. 1, connected to a single-phase network Main circuit comprises a consumer 1 connected in series, a thyristor 2 and the coil 3 of the control electromagnet one Switch, the changeover contact 4 of which is parallel to the thyristor 2. The control electrode of the thyristor is connected to a resistor 6 fed from a direct current source 5. In the idle state, the control electrode is connected to contact 4 and a closed-circuit contact M at the potential of the cathode of the thyristor, so that it is blocked.

To switch on, the contact M is pressed briefly; thereby the control electrode of the thyristor 2 becomes positive and it becomes conductive. The coil 3 of the electromagnet, through which a current now flows, switches the main contact; through this the thyristor 2 is short-circuited after the connection of its control electrode to its cathode is finally severed is, so that the button M can be released and the thyristor 2 then remains conductive.

The movement of the changeover switch is very slight, i.e. it closes very quickly, and the thyristor also remains only a very small amount switched on for a short time, so that it can be considerably overloaded can: a thyristor with a relatively low load capacity can be used, the rated current of which is considerably lower than that to be switched Electricity can lie.

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To open the switch button A is pressed, the one Working

& eta * contact actuated, which bridges the coil 3. Through this ia «xi8t» ngKL stops the excitation of the electromagnet and the Changeover contact 4 returns to its original position. During the movement of the contact 4, the current flows through the thyristor so that sparks are avoided when opening. Then will when the second contact is closed at the end of the switch stroke, the control electrode is put back to cathode potential, see above that the thyristor 2 blocks as soon as the current goes through zero » goes through. The current flowing through the resistor 6 is im Retirement is very low, so that the power dissipation is negligible.

In the practical application of this principle, the changeover contact 4 is divided into two simple contacts, i.e. one for the main current and one for the control current] the control current contact or auxiliary contact is preferably a vacuum contact or even a semiconductor switch. In the same way the contact A for short-circuiting the coil 3 is only a low-current contact. Finally, depending on the application, a diode is connected in anti-parallel to the thyristor.

The main circuit shown in FIG. 2, which is connected to a single-phase network, contains, in series connection, a consumer and an anti-parallel hold of two thyristors 2 and 7, to which the contact 4a of a contactor is held in parallel. The excitation coil 3 of his electromagnet is in series with a normally closed contact A ₁ at the terminals of the consumer 1. At the end of the stroke of the armature an auxiliary contact 8 opens or 11 and 12 connected. A resistor 13 in series with an Arbeltkontakt M. connects the control electrode of the two thyristors to one another. The auxiliary contact 8 is parallel to the contact M ₁ .

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The switch arrangement is shown in the switched-off state. To switch on the contact M, is closed briefly. When the diode 10 is conductive, it lets the control electrode of the thyristor 2 become positive via the resistor, so that it becomes conductive. In the following half cycle, the thyristor 7 becomes conductive, since the diode 12 has become permeable. The resistors 9 and 11 in parallel with the corresponding diodes stabilize the control electrode circuits. Therefore, current flows in the consumer regardless of the half-period, coil 3 is energized, contacts 8 and 4a close one after the other, which above all _{ensures that the thyristors continue to fire after the actuation button of contact M 1 has been released} and that the thyristors are short-circuited . For this reason, the contact 4a is immediately short-circuited by the thyristors in the event of a bounce back, thereby avoiding any risk of spark formation.

To switch off, press the button that opens contact A. whereby the excitation current of the electromagnet is interrupted. The contact 4a is opened without radio formation, since the current flows through the thyristors, and at the end of the stroke the contact 8 opens, whereby the blocking command is given to the thyristors is so that this eöschen as soon as there is electricity in the consumer passes through zero.

In Fig. 3, another embodiment for the ignition circuit of the thyristors 2 and 7 is that described above Circuit shown. Each control electrode is connected in series with the cathode of the respective thyristor via a resistor direction with a zener diode of the appropriate sense of direction and 16 and 15 and 17, respectively.

Fig. 4 shows a modified circuit diagram of a single phase holding in which the main circuit is connected in series

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Consumers 1 and each includes an anti-parallel connection of a diode and a thyristor. A mechanical contact 4b is parallel to the anti-parallel circuits. He's going through an electromagnet controlled, the coil 3 of which is in series with the primary winding of a transformer 20 and with a resistor 21 is connected to the terminals of consumer 1.

A normally closed contact A ₂ is connected to the secondary winding of the transformer 20. When the circuit of the secondary winding is interrupted, the impedance of the primary winding of the transformer is sufficient to practically interrupt the excitation current in the coil 3.

An auxiliary AC power source 22 feeds through a resistor 23 the primary winding of the transformer 24 of a rectifier circuit 25 and 26, which supplies the control voltage for the thyristors via resistors 27 and 28.

/ rest An auxiliary contact 29 actuated with the main contact 4b is located in series with a normally closed contact Mg at the terminals of the primary winding of the transformer 24. To switch on the contact Mg is opened briefly in order to apply the control voltage to the To put thyristors, which are conductive and allow a current to flow through the coil 3, so that successively

the contact 4b closed and the auxiliary contact

29 can be opened as in the previous example.

Switching off takes place by briefly opening the contact A ₀ , whereby the excitation of the electric agent is canceled, ^ er
so that / returns to its rest position and its contact sequence takes place in the opposite sense.

Fig. 5 shows a circuit diagram for a symmetrical three-phase system. _{The phase loads 1 R} , Ig, and!, Ρ of the consumer are connected to the terminals R, S and T of the network

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are connected in series with a Antlparalleleohaltung from a diode and a thyristor 7 _R and 2 _R , 7 _g and 2 _g or 7 _T and 2 _T , the ends facing away from the load are together. As long as no thyristor has been made conductive, no Strom.Im shunted to each Antiparallelschal device is a contact 4 _R , 4 _g and 4- ,, which are controlled by the contactor, whose solenoid 3 in series with a normally closed contact A, and one Resistor 21 is connected to the terminals of the phase _{load 1 R of} the consumer. An auxiliary break contact 29, which is also operated by the contactor, is connected in series with a break contact M and a resistor 6 and is connected to the terminals of a direct current source 5 in order to control electrodes _{via resistors 3O D} , JJO ₀ and 3O _n to polarize the corresponding thyristors. The mode of operation corresponds to the Pig single-phase circuit. 4, where the contacts A, and M, act directly on the controlled circuit, while the contacts A ₂ and Mp both act via a transformer.

Within the scope of the invention, that shown in FIG. 5 can be used Star connection of the mechanical contacts can be replaced by a delta connection in such a way that every contact between the connection point of a phase load with the anti-parallel connection of two adjacent phases, i.e. similar to the one in Flg. 4 shown single-phase hold.

In the switch arrangements described above, the mutual The dependency of the mechanical contacts and the semiconductor valves lying parallel to them are thereby ensured, that in the control circuit of the valves one with the actuating mechanism the main contacts are permanently connected to the auxiliary contact.

.A

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The same sequence of operations can be used for other switch designs for example also by a suitable choice of the time constants of the control circuits of the main and auxiliary contacts achieve. The invention also relates to such circuits with electrical interlocking of the control circuits of the respective Contacts. It is essential that the controlled valve is made conductive first and remains in this state, and immediately afterwards the mechanical contact is closed, while the reverse order for the rest position takes place: first there is mechanical contact without sparking opened, because the valve lying parallel to it remained conductive, and then the valve is blocked.

In the case of a purely electrical lock, an and the same auxiliary power source via a single circuit breaker that serves as a switch-on and switch-off pushbutton that feeds the various control circuits. Fig. 6 shows such an electrical one Locking.

The load Iq of the phase R is in series with the thyristor 2 ", to which the mechanical contact 4" and the Diet !; J ^ are oppositely connected in parallel. The coil 3 of the electric magnet is connected to the terminals of the auxiliary power source 31 for a direct current or a rectified alternating current via a switch 32. A potentiometer 33 "that is connected to the same power source through the same switch, supplies through a diode 3 and a resistance 35 ^ permanently a control voltage for the control electrode of the thyristor 2 _R. A second potentiometer 36, which is held in parallel with the first one, charges the capacitor 37, which feeds the resistor 35 via a diode 38. As a result of the capacitor 37 «whose discharge into the potentiometer 36 is prevented by a further diode 39, the circuit feeds the control electrode of the thyristor 2 _R with a delay. Therefore, when the switch 32 is opened, the circuit of the potentiometer 36, the capacitor 37 and the diode 38 hold the thyristor 2 «

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ignited so that contact 4 _{R has} enough time to open without sparking. The time constant of this delay circuit only has to be greater than that of the electromechanical disconnection device of the contactor.

When the switch 32 is closed, on the other hand, a control voltage is immediately applied via the circuit of the potentiometer 33 *, the diode 34 and the resistor 35 to the control electrode of the thyristor 2 ^, while the contact 4 " _{closes shortly after the thyristor 2 P} has been made conductive . The time-

is the constant of the circle of elements 34 and 35 / negligible and therefore always smaller than that of the electromechanical Contactor control device.

The desired sequence of operations is thus obtained in that the time control circuits of the control circuits are dimensioned in such a way that that of the electromechanical control device of the mechanical Contacts always smaller than the time constant of the Verltungen 1st, each control circuit having two in parallel, one of which and the other responds with a delay. As a result, the desired current flow sequence is always achieved.

Instead of the valves connected in anti-parallel, for example also a valve like a "symmetrical thyristor" with two line directions, of which at most one is continuously conductive, can be used.

The switching sequence described results in voltages of a mechanical, electrical and thermal nature, which The main causes of wear and tear are avoided. The uncritical simple control results in a very high level of reliability.

Patent claims:

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Claims (14)

Claims 1) Switch arrangement for switching on and off an AC powered Load with / a mechanical main contact semiconductor valves connected in parallel, which through an auxiliary contact actuated depending on the main contact can be switched, characterized in that, that the semiconductor valves are anti-parallel connected semiconductors (2,7), of which at least one is controllable and with its control electrode using the mechanical auxiliary contact (8) before the main contact is closed (4) is switched to open mode and after opening the main contact to blocking mode, and that the actuation circuit (3) for the main contact is parallel to the consumer (1). 2) switch arrangement according to claim 1, characterized in that the valve control circuit is one of Has manually operable pressure contact (M). 3) switch arrangement according to claim X, characterized in that that the main contact actuation circuit has a manually operable pressure contact (A). 4) switch arrangement according to claim 1, characterized in that with a single-phase current a single one Antiparallel retention (2.7) is provided. 5) Switch arrangement according to claim 4, characterized in that two series-connected anti-parallel circuit tungen (2,18; 7,19), their corresponding elements opposite Have forward direction, are connected in parallel to the mechanical main contact (4) (Fig. 4). 909832/0642 ., ut. £ 3g <ii. v. 6) switch arrangement according to claim 1, characterized in that in a three-phase system for each Phase (R, S, T) a mechanical main contact (4R, 4s, 4T) with an anti-parallel connection (2R-7R, 2S-7S, 2T-7T) in parallel is switched. 7) switch arrangement according to claim 1, characterized in that g e k e η η, that in a three-phase system with star-connected consumer elements, the main mechanical contacts in the triangle between the common points of the consumer elements and the anti-parallel connections of each phase are switched. 8) switch arrangement according to claim 1, characterized in that for the mutual dependence of mechanical contacts and the controlled semiconductor valves an electrical interlocking of the respective circuits by choosing the time constants of the electromechanical Control circuit of the mechanical contacts is provided with regard to the time constant of the valve control circuits and that a single power source (31) via a single, as On and off pushbuttons formed switch (32) feeds the control circuits connected in parallel. 9) switch arrangement according to claim #, characterized in that the tent constant of the electromechanical The control circuit of the mechanical contacts is smaller than that of the control circuits for the delayed action controlled valves is. 10) Switch arrangement according to claim 8, characterized in that the current source common to the control circuits (31) is a source of constant oil or rectified alternating current. 909832/0642 11) Switch arrangement according to claim 8, characterized by two potentiometer circuits serving to control each valve (2R), the potentiometers (33 * 36) of which are connected in parallel and one of which as a switch-on circuit (33 * 3 ² O has the smallest possible time constant, while the other as the switch-off circuit (36,39,37,38) has a greater time constant corresponding to the desired switch-off delay (Pig. 6). 12) Switch arrangement according to claim 1, characterized in that the controlled valves are thyristors are. 13) Switch arrangement according to claim 1, characterized in that the controlled valves are symmetrical Double thyristors with two forward directions are, of at most one of which is kept in the lead. 14) Switch arrangement according to claim 1, characterized in that g e k e η η draw t that the actuation of the main and control contacts in a manner known per se as with subsequent contacts one after the other with the other way around in the opposite direction Order happens. 909832/0642 -41 ' Blank page