DE2315208A1 - CONTROL LOGIC FOR ELECTRICAL POWER SUPPLY SYSTEMS - Google Patents

Description

DR. MOlLER-BORE DIPL-PHYS. DR.MANITZ l) I ° L. CHEM. DiI. DRUFEL DIPL-ING. PINSTERWALD dipl-ING. GRÄMKOW

PATENT LAWYERS

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ti να 1973

f sharp / F 1089

George Donald Forman

56 Addington Road,

West Wickham, Kent / England

and

St Paul's Engineering Company Limited, Printing House Square,
London EC4P 4DE / England

Patent application

Control logic for electrical power supply systems.

The present invention relates to the control of electrical power systems, and more particularly to the control of groups of electrical devices or groups of energy-consuming elements within a single device, these devices or elements being operated so that they an average Consumption of electrical energy that is much smaller than any maximum consumption.

In a conventional electrical installation in which a number of devices from a common Power source are fed and all devices can be turned on at the same time, the

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Power line the total maximum power demand of all with simultaneous operating devices and the source of supply be able to use these total maximum To cover power requirements. In addition, at large electrical Installations approved by the authorities for the electrical Utility grid fees often and sometimes very pronouncedly based on the peak power requirement of the installation addicted. Thus the endeavor to reduce the peak power requirement as far as possible can be explained.

A feature of many types of electrical equipment, and particularly electrical equipment with electrical Heating elements consists in that the maximum power demand is much greater than the normal average power demand is. Such devices are usually thermostatically controlled, and under normal working conditions, the "off" periods of the thermostat are long compared with the "on" periods. Nonetheless, must the management of an installation containing several units of such a facility for the possibility be provided that all thermostats are switched on at the same time. Similar considerations apply to a Apparatus which includes several independently controlled heating elements, such as an electric cooker.

It has been proposed to create installations in which the maximum load is applied to the power source

is controlled by arranging that an increasing number of parts of the load are turned off by a "stabilizer""as soon as their combined consumption increases" so that the total consumption is limited to a predetermined level, the order of in which these parts are switched off according to a predetermined scheme of priorities. So it has been suggested that

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Load parts of the same priority in such an arrangement are separately connected to the stabilizer ¹¹ by a commutation arrangement, so that their positions in the priority scale are periodically exchanged and over the long term current is distributed to such loads of the same priority according to the average priority level of the connections between the commutation arrangement and the stabilizer will.

A disadvantage of such systems of this nature that have been proposed is that the various Load parts are completely disconnected from the supply source when there is a load or consumer shedding takes place, with the associated switching operations, although they demand below a maximum value cause temporary fluctuations in exposure, which not only lead to radio interference, but can also cause undesirable fluctuations in the supply voltage, especially when the consumers are switched are great.

Power control systems for AC power sources are well known in which thyristors or other related semiconductor devices such as triacs are used. These systems are of two main types. The first system of the phase control type relies on the change of the peak at each main cycle or change main cycle of the power supply at which the control device is switched on. This type of control creates severe radio interference and problems with the power factor, so that it is not suitable for installations with significant power consumption. The other "burst fire" system in which control is done by controlling the frequency and length of the periods or "bursts ¹¹ " for which the control device

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is switched on for an integer number of half cycles, overcomes the problems of the phase control method lays however, a fluctuating consumer to the supply source. In addition, this is the frequency of this fluctuation particularly disadvantageous if the duration of the impact ■ is proportionate is short.

The aim of the present invention is to provide a device for limiting the peak power demand an installation or device that has a number of individually controllable electrical loads or consumers or groups of consumers, this device not having the disadvantages discussed above.

The device according to the invention for the distribution of electricity from a single AC power source to a number of consumer units with approximately the same amount of power consumption, the individual control devices are assigned, has thyristors connected to each of the consumer units are connected in series, as well as a device for generating a continuous sequence of pulses, which are timed so that they essentially coincide at the zero crossing points of the alternating current source, furthermore a control logic which is operative to direct pulse trains and various thyristors or various combinations of these thyristors for successive whole numbers of half cycles, respectively a continuous programmable sequence and a device for programming the Logic according to the state of the individual control devices that are assigned to the consumer units.

The term thyristor is used every week, it being understood that the two-way devices such as Triacs, which are for use in the present case

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are preferred, as are functionally equivalent but now obsolete devices such as thyratrons.

The term consumer units refers to any electrical device or an individually controllable one Element within this device or on any combination of devices or elements with Chargeable electricity consumption when switched on.

The control device for the consumer units can be manually or automatically operated switches, thermostats or transducers of any type which can generate a control signal, the control device so can have the effect that either the circuit to the units assigned to it is interrupted and a state is created will be determined by the programming device can, or preferably acts directly on the programming device.

The control logic is preferably driven forward through its sequence by clock pulses passing through the division of the frequency of the AC power source are generated.

The invention is described below and with reference to the accompanying drawings described; show in it:

1 shows a simplified block diagram of parts of an electrical household installation with a number of electric storage heaters;

Fig. 2 is a simplified block diagram illustrating the hot plate system of an electrical Household cooker;

3 shows a simplified block diagram of an industrial installation with four similar heating plates;

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4, 5 and 6 circuit diagrams of different embodiments of the device according to the invention.

1, 2 and 3 show typical uses of the device according to the invention, which for the purpose of Description in connection with the drawing figures is shown as a "black box", denoted by the reference numerals 5 (Fig. 1), 25 (Fig. 2) or 31 and 33 (Fig.3). is provided and has certain functions. How these functions are achieved is explained with reference to the Fig. 4, 5 and 6 described in more detail.

Referring to FIG. 1, an electrical household installation has, for example, four electrical storage heaters 1-4, which in turn are only considered, for example, as each having a nominal output of 3 kW. These radiators are connected to a fuse and distribution box 5, this box being connected by a cable 6 to a measuring and time switch 7, which in turn is connected by a further cable 6 to a main fuse 8 through which the remainder 9 of the installation is also supplied. The fuse "8 is connected to a supply network 11 by a cable 10. In a conventional installation, the timer 7 switches all four radiators 1-4 on at the same time and since their temperature has usually dropped enough for their heating elements to be integrally formed in the radiators Thermostats can be thermostatically switched, the cables 6 must have a nominal power of 12 kW load and the contacts of the timer 7 have a similar nominal power, whereby the fuse 8 and the cable 10 must have a nominal power of 12 kW beyond the load _s through the rest 9 of the installation is imposed _o If many households in "the neighborhood have the same heating installations _p an increased nominal power for the supply network 11 is required, whereby the sudden-

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borrowed increase in load or consumption to a certain extent Times of the day when all or most of the radiators are on at the same time also contribute to problems the maintenance of the supply voltage within the legal limits.

Assuming normal settings of the radiator thermostats, the individual radiators usually require no more than a fraction of the total "ΕΪΝ" period allowed by the timer 7 to reach a temperature which will cause their thermostats to turn them off, whereupon only short periods of electricity use are required to keep them "populated" to the desired temperatures set by the thermostats for the remainder of the "ON ^M" period. A graph of consumption versus time would thus show an initial period of 12 kW demand, which drops to zero after a few hours, apart from occasional periods of probably no more than 3 kW demand for "replenishment" purposes.

Obviously, it would be desirable to bring this current demand to a mean value in order to broaden it spread over the available "ON" period while the maximum demand is reduced. This can be done by in the distribution box 5 according to the invention Device is included which is effective to supply electricity to each radiator for as long as the thermostat assigned to it maintains this in the circuit. Through an arrangement that programming the device is controlled depending on which radiators are switched off by their thermostats or otherwise it can be guaranteed that an increasing proportion of the energy supplied goes to the other radiators

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is derived when each radiator is removed from the circuit is switched off while the load on the supply source remains constant

Fig. 2 shows the application of the invention in an .electric Cookers with heating plates 21, 22, 23 and 24, two of these plates (for example) having a rating of 2 kW and the other two have a nominal power of 1 1/2 kW. Each hot plate is usually with one independent control device as s.B. a "boiling act" provided, this device being effective to switch the heating plate which controls it on and off, where the mark space ratio of this switching process · accordingly the setting of the control can be adjusted to maintain different hotplate temperatures. It it is clear that with such a system it is possible that all hot plates draw power at the same time, although the setting of their controls is quite low and the current demand for the power source is rapid can fluctuate sharply between 0 and 7 kW. However, the independent control by the invention Device 25 replaces which is effective to keep current of each switched-on hot plate in a continuous • Order of bumps to be fed, with individual hotplate controls 26 control programming facilities in device 25 so that the entire "ON" period each hot plate is controlled in this order, this problem can be overcome. The whole Electricity requirement of the cooker cannot exceed that of the hotplate with a maximum rated power, whereby the versatility of operation of the cooker is somewhat reduced, but in some circumstances this does so Disadvantage is outweighed by the advantage, which consists in that the peak current requirement by this arrangement and the fluctuations in electricity demand as well as the electricity

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nominal power required for power line 27, be reduced. While the ratings of the hot plates are different, they are sufficiently approximate, do to avoid strong fluctuations in the load on the power source.

Fig. 3 shows the object according to the invention when it is used in an industrial installation, which for example has four crucibles 30, which heating elements with a nominal power of 20 kW for each crucible to have. In a conventional installation, the power rating of the line must be based on the installation calculated, that the heating elements of all four crucibles can be switched on at the same time and this corresponds to a peak demand of 80 kW, whereas the average demand is only very low Fraction of this value.

The crucibles are each provided with a power source 35 through a control device 33 according to the present invention connected, the programming device of which is controlled by signals transmitted along feedback loops 32. are transferred back from thermostats 31 in the crucibles 30. The control device 33 switches one after the other those crucibles on and off whose associated thermostats have closed contacts, indicating that the crucible temperature is below a desired level. The melting pigs, whose thermostats have open contacts are excluded from the sequence.

Referring now to Figure 4, that figure shows one embodiment the device 33 (see Fig. 3) according to the present invention. Consumer or load units Lt, L2, L3, L4 (for example the crucibles 30 according to Figure 3)

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are connected between the current-carrying and the neutral lines ACl and ACN of an alternating current supply network by triacs T1, T2, T3 and T4. As shown, each consumer unit is connected to a manually controlled switch and / or thermostatically controlled contacts, which are represented by switches S1, S2, S3 and S 4. These switches act to close or interrupt current circuits, regardless of those which contain the triacs and the loads or consumers, although the switching arrangement shown in FIG. 3 can also be used as described below. The switches are connected via inputs 1A, 2A, 3A and 4A to a programming device for control logic, the latter having data selectors H1, H2, H3, H4 which are assigned to the triacs T 1, T2, T3, T4. The outputs 1B, 2B, 3B and 4b of the data selectors are used to select gates MI, M2 _? M3, M4 to be scanned, a square wave with mains frequency being applied to each port, which is generated by a pulse generator, which is generally provided with the reference number Y and has a flip-flop circuit, which is formed by cross-coupled gates A, which are driven by cut-off pulses that are derived from the power supply network by means of a transformer TXj, resistors R5 and R6 and Zener diodes Z1 and Z2 *

The outputs of the gates MI · = ■ M4 are applied to the gates of the triacs T1 - T4 by power amplifiers and / or pulse transformers X1 - X4, which set the amplitude ^ source impedance and the shape of the outputs of the toie ₉ to alternate positive and negative pulses Beginning of each half cycle of the alternating current supply, which are suitable for firing the triacs. The inclusion of transformers or optical isolators in the circuits X1 X4 is essential if the rest of the device is of the

Circuits to be electrically isolated, -which the Contain triacs T1 - T4, as is often desired for safety reasons.

In another arrangement, the circuits X1-X4 are through. Zero voltage switch of the type that is used in an integrated Circuit shape are well known, a typical example being CA3O59, sold by RCA, is. Since these integrated circuits provide a circuit arrangement for generating expediently timed and shaped pulses from an AC power supply network, the connection to the pulse generator can be omitted are, just like the gates M, with the output lines 1B, 2B, 3B, 4B directly connected to a TTL circuit compatible lock input connected to the zero voltage integrated circuit *. To get correct polarities too received, lines 1B, 2B, 3B and 4B should be inverted Outputs are connected, which are provided at the selectors H1 - H4.

It can therefore be seen that the outputs of the data selectors for driving pulses from the generator Y are closed the triacs to which they are connected to thus route the circuits to the assigned loads or consumers L1 - L4.

The data selectors are made by the programming device programmed in the form of the line which, they with the Connects switches S1 - S4, the latter being connected to act when they are closed, around the lower end of the associated response resistors R1 - R4, which at their upper ends with the positive Logic power supply rail connected to the base rail (not shown) of the logic power supply short-circuit, as a result of which a logical O is applied to those inputs of the voters who are connected to each of them

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Way short-circuited response resistor are connected. In the example discussed here, all inputs are negative logic inputs «, A sampling input s_ on each selector H1-H4 is connected to resistors R1, R2, R3, R4, which ensures that a data selector is only effective when the switch, which is connected to its associated circuit is closed. The switches S1 - S4 are also in various combinations to the program ereingänge a, b und__c every voter connected _e

Depending on which input or which combination of inputs a, b_ and £ on a selector to logic 0 has been brought, the logic state of one of the eight inputs shown in the drawing is as they enter the top of each selector H1 - H4, applied to the associated gate MI - M4. From these entrances one at each voter is constantly withdrawn, whereby the remaining in different arrangements for each voter with different of the nine outputs ti - t9 one Pulse generator and control circuit are connected, which the counters, indicated generally at X and Z. are and which each act to provide appropriate sequences of sampling pulses for the election by the voters H1 - H4 and from there to be delivered to the gates MI - M4 for a selective application «

The pulse generator and control circuit firstly has a “divide-by-S counter ¹ ? X with two JK flip-flop circuits D, a NAND gate N together with output NOR gates E, three sets of It supplies initial pulses with a token space ratio of 1: 2 with 120 ° phase-reversed from one another to the lines t3 »t4, t5. It also has a" divide-by-four counter ^M Z, which

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Circuit F1 is formed, the output pulses with a token space ratio of 1: 1 and in phase opposition to the lines ti and t2, as well as to a JK flip-flop circuit F2, which in connection with the gates G four sequences of pulses of a token space ratio from 1: 3 to lines t6-69, each sequence being 90 ° out of phase with the preceding sequences. The pulse generator and control circuit is clock-controlled by pulses derived from the output of the pulse generator Y after passing through a clock pulse generator W, which in the present example is formed by two cascaded "divide-by-i 6" counters ¹¹ B and C However, the ratio of the divider is an arbitrary choice depending on the length of the period desired for the pulse generator and control part Z, which in turn depends on the nature of the loads L1-L4 the loads heat loads with a large thermal inertia, a long period is readily acceptable, whereas loads of a small inertia require a short period if the operation is to proceed smoothly any suitable square wave generator can be used to generate clock pulses, but it is desirable that d ie clock pulses are timed in such a way that they begin and end in a certain relationship to the phase of the power supply network and thus contribute to avoiding undesired responses in the control logic.

The connections of the lines ti - t9 with the data inputs of the voters H1 - H4 are in relation to the programming of the inputs a, b and £ of the voters by the Switches S1 - S4 arranged so that only when a switch is closed, the associated gate of the gates MI M4 is continuously scanned when two switches are

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are closed, the inputs from lines ti - t2 are connected to the two assigned gates of gates M1 · * · M4. _v applied so that the gates are alternately scanned for half the time? if three switches are closed, the inputs from lines t3, t4 and t5 are applied to the assigned three gates of gates M1-M4, so that the gates are scanned one on the other, for a third of the time? and if all four switches are closed, the inputs from lines t6 - t9 are applied to all four gates of gates M1 - M4, so that the gates are scanned one after the other for a quarter of the time. L4, which are assigned to the gates M1'-M4, are thus in turn supplied with energy for suitable periods corresponding to an integer number of half periods. If the state of one of the switches S1 - S4 changes, the selectors HI - H4 are immediately programmed again, this programming being effective in order to direct the next following pulse from the pulse generator Y to the appropriate triac according to the new program Pulses that mark the beginning of every half cycle of the power supply network ". always directed towards one or the other of the loads L1 - L4.

The circuit arrangement used here was not described in more detail. In any case, it is in the drawing as a Device using standard 74 series TTL integrators shown, the identity of the integrated circuits used in most cases in the Drawings along with pin numbers according to the Dual-in-lead versions of these circuits are shown are. Gates A, N, and M are through 74QQ quadruple NAND gates and gates Ξ and G are through 7402 quadruple NOR gates educated. The person skilled in the art is aware of how

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Circuit can be expanded to handle a larger number of loads or alternate groups of logic too use or how to use them at a purpose-built facility integrated circuit can be revised.

It may be desirable, or more convenient when existing installations are modified, to switch S1 - S4 in To switch series with the consumers, as shown in Fig. 3. In this case, a device must be provided in order to determine whether the circuit containing a particular triac arrangement is not interrupted and to determine whether it is appropriate to apply logic signals to the input lines 1A, 2A, 3A, 4A. However, there is contact arcing usually leads to the mechanical shutdown of a load-bearing circuit and it to the end of a half Period is ineffective, the switching of a load while it is being supplied with current is too late for the control logic scanned in order to be programmed again in good time and the next ignition pulse to a different one Triac order to be addressed. Therefore, the arrangement described above, with the switches S1 - S4 in separate Circuits control the logic directly, preferred.

FIGS. 5 and 6 show two alternative embodiments of the device 33 (see FIG. 3), the output lines 1B-4B controlled circuit is omitted as it is similar and subject to similar modifications like that of Fig. 4.

In Fig. 5 pulses from a clock W, the Clock W in Fig. 4 is similar to that used to control a two-level Johnson counter which has two expedient having connected flip-flop circuits N of the D-type with preset and enabled inputs S and R, which for setting the counter to any level

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in "its counting cycle depending on the determination a certain stage in the counting cycle by a system of NOR gates P and Q can be used, this system both in relation to the determined level (by means of the gates p) as well as the counting level can be programmed * by means of the s and R inputs are set as a function of the determination of the previous stage (by means of the gates Q). This programming corresponds to the logical value of an the inputs 1A, 2A, 3A, 4A, depending on the state of the switches S1, S2, S3, S4 (see above) is applied. The Q and Q outputs of the counter stages are decoded by further NOR gates T and sent to the outputs IB,. 2B, 3B-, 4B, which control circuitry pulses, too the triacs T1, T2, T3 and T4 as with the previous off- management style, controls. The decoding gates T become scanned through the input lines by the inverter I, thus reducing the possibility of unwanted pulses Avoid appearing on an output line when its associated switch S1 - S4 is open.

As can be seen from considering the circuit, is the control logic of the type that the counter only in counting stages which logical 1 outputs can remain in the output lines corresponding to the input lines that generate a logical O input (i.e. inputs that: a Switches S1 - S4 are assigned, which is closed). Therefore, when the counter is clocked », cause that gate pulse trains one after the other on those Triacs T1 - T4 are directed, which with the switches Sl - S4 are connected, which are closed.

Fig. 6 shows an alternative arrangement in which the Clock pulse generator W is used to add a ring counter control the four flip-flop circuits DI, D2, D3, and D4 of the D type, one for each load, which should be controlled, where they are connected and

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to form a slide register. The output lines 1B, 2B, 3B, 4B are connected to the Q outputs of the flip-flop circuits D1 - D4, the register being pulsed is clock-controlled from the clock pulse generator W, which is similar to the pulse generators W described above. When a If a single bit enters the register and is circulated by clock pulses, each output line becomes in turn brought to the high state, whereby an ignition pulse sequence is driven to its associated triac arrangement T1 - T4 will. The input lines 1A, 1B, 1G, 1D are however, used to control a system of gates which program the ring counter to count on those Flip-flop circuits D1-D4, which are assigned to the input lines 1A-4A, their assigned Switches S1, S2, S3 and S4 are open. So they are Flip-flop circuits are switched into the register, in which the Q output of a flip-flop circuit with the D input of the next flip-flop circuit is connected through NAND gates J1 - J4, while the programming inputs applied by the inverters K1 - K4 and thus used when they go down to sample NAND gates E1-E4, each of the D input of one of the flip-flop circuits Apply D1 - D4 to gate J1 - J4 of the subsequent flip-flop circuit. The associated reverse Input 1A-4A is also applied to the reset input R of the flip-flop circuit via a NOR gate N1-N4, which should be bypassed so that the assigned output 1B-4 B remains at the logical 0 value.

Measures must be taken to start the register by introducing a single binary number and to prevent it from operating in the wrong mode. For this purpose, the Q outputs of the flip-flop circuits D1 - D4 are applied to a decoder, which is generally ■■■ -. nen is shown at S, where it is initially effective> um

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to determine a state of the ring counter in which all Q outputs to which it responds are low by sending a digit to flip-flop circuit D1 an additional input is created at gate J1. The decoder also determines a condition in which more than one of the Q outputs is high, to which it responds by resetting all of the flip-flops, The decoder has a decoder DG, with a binary coded decimal of which the 0, 1, 2, 4 or 8 outputs with a NAND gate and from there through an inverter to the NOR gates N1 - N4. Of the O output is also connected to port J1. The presence a 0 output from the decoder corresponds to a state of the counter in which all Q outputs are low are, where the absence of a 0, 1, 2, 4 or ν 8 output corresponds to a state of the counter in which more than one of the Q outputs is high.

It can be seen that this embodiment easily can be expanded to include a device for controlling any desired number of loads obtain. >. . .

It is also evident that the embodiments described above are only given by way of example. Logical systems can be used which allow groups of loads to be supplied with current at the same time, provided that these groups ¹ always have a similar total consumption. Similarly, provision can be made for the periods for which various loads are powered to be changed from one another, or for selected loads or loads to be used more than once in a single one. Switching cycle are to be supplied with power. One way by which this can readily be achieved is by using any of the previously described

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two embodiments are used, but a pair of Inputs and outputs are connected in parallel to to serve a single consumer.

Claims

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Claims (1)

231520 Claims (1 »J Device for distributing power from a single AC source to a large number of consumer units with individual control devices which have thyristors which can be connected in series with each of the consumer units, as well as a device for generating a continuous pulse train which is time-controlled are to essentially coincide with the zero-cross points of the AC power supply, characterized by a control logic (X, Z, H1-H4, MI-M4 | N, Tj D1-D4), which is effective to direct successive pulse trains in order to switch on different heights of said thyristors (T1 T4) or that those combinations thereof for successive whole counts of half periods of supply according to a continuous programmable sequence, a device (1A - 4A; P, Q: K1 - 4, J1 - 4, El - E4, Nt - N4), which is logical according to the state of the individual control devices, "the are assigned to the consumer units (L1-L4) and by a device (W) which controls said control logic through said sequence, • 2. Device according to claim 1, characterized in that that the programming device (1A-4A, Ra-R4; P, Qj K1 - K4, J1 - J4, E1 - E4, N1 - N4> immediately through, manually, thermostatically or otherwise automatically operated switches. (S1 - S4) is controlled which the Form control device for the consumer units. 3. Device according to claim 1 or 2, characterized in that that the clock control device (W) by a factor contained in a number of the frequency of the alternating current source α> ΐ4ί /) Τ ('* 6ί * «^« ifvy / rt-tersynchronously synchronized is. 309841/088 3 4. Device according to one of the preceding claims, characterized in that the control logic means (X, z) for deriving a number of different pulse trains from a clock pulse train which is generated by the clock control device (W), as well as a selector device (H1-H4) which is generated by the programming device (1A - 4A) is programmable to make different choices of different pulse trains select and a gate device (Ml - M4) which is actuated by the selected pulse trains to direct the pulses from the pulse generator (γ) to various of the thyristors (T1 - T4). 5. Device according to one of claims 1-4, characterized in that the control control is a programmable Counter (N or D1 - D4) and a gate device (MI - M4), which by the counter according to the level of its counting can be actuated to differentiate the pulses from the pulse generator of the thyristors (T1 - T4), the counter being controlled by the programming device (P, Q or K1 - K4, E1 - E4, Jl - J4, N1 - N4) is programmable, in order to count along counting levels that are triggered by the control of the pulses to certain thyristors (T1 - T4) are connected, according to the state of the control device (S1 - S4), the consumers or loads (L1 - L4) are assigned, which are controlled by these thyristors. 6. Apparatus according to claim 5, characterized in that that the counter is a ring counter. 7. Apparatus according to claim 6, characterized in that the counter is a Johnson counter. 309841/0883