DE1084761B - Electronic switch for consumer circuits fed from an alternating current network - Google Patents

Description

In the main patent application there is an electronic switch for powered from an alternating current network Consumer circuits specified, which works like a current gate with gate control. It consists of transistors which are fed back supercritically by means of a saturation-free current transformer. The gear ratio of the current transformer may be at most equal to the current amplification factor of the transistor. Since the tax performance is almost entirely is taken from the consumer group, you can get by with small tax rates. As transistors are used Advantageously, silicon transistors are used, with which one consumes power in the order of magnitude can control from kW.

In the main patent already different arrival have been given application possibilities ¹ S 'for the new electronic switch. In this case, a valve is usually connected in series with each transistor, which valve impresses the direction of the current on the collector circuit. Full-wave rectifiers, anti-parallel circuits, etc. can be built from this basic element.

Closer investigations have shown that the maximum achievable output power with the today available silicon transistors not through the heating, but solely through the height the maximum permissible collector current is limited. This leads to what is surprising at first glance The fact that two transistors in two-way or anti-parallel connection do not have any higher performance can dominate as a single transistor when this both half-waves of the AC mains voltage controls.

For such an electronic switch for consumer circuits fed from an alternating current network with a transistor that is supercritically fed back via a saturation-free current transformer is that the transformation ratio of the current transformer is at most equal to the current amplification factor of the transistor, based on the above knowledge, according to the invention, the transistor in already otherwise proposed way arranged in the direct current branch of a Graetz bridge and the The feedback stream supplied by the converter is rectified by another Graetz bridge.

Exemplary embodiments of the invention are shown schematically in the drawing. Fig. 1 relates on the control of a consumer alternating current. The transistor 1 is in the direct current branch one Graetz bridge 6, so that the current only flows through it in one direction, but both half-waves can control. The primary winding is in series with the Graetz bridge and the alternating current consumer 11 3 of the current transformer 2 arranged. The secondary winding 4 feeds via a Graetz bridge Electronic switch

for from an alternating current network

powered consumer circuits

Addition to patent application S 57104 Villa / 21 a *
(Exhibition guide 1 061 823).

Applicant:

Siemens-Schuckertwerke

Corporation,

Berlin and Erlangen,

Erlangen, Werner-von-Siemens-Str. 50

Dipl.-Ing. Rudolf Weppler, Nuremberg,
has been named as the inventor

13 the feedback loop. To control the transistor, a control set 21 is provided, which as in Switch can be designed according to the main patent. The tax variable supplied by it leads in opening of the transistor for each half-cycle, which is then completed by the feedback. A Resistor 7 is used for decoupling from the feedback circuit.

In the arrangement of Fig. 1 still further circuit elements are shown, which are useful for the practical Operation have proven beneficial. For example, it has been shown that with purely ohmic Do not load the consumer voltage of the mains voltage right up to its point after the »ignition« has taken place Zero crossing follows, but the transistor blocks just before the zero crossing, so that the Working current suddenly cuts off. However, this leads to the fact that in the secondary winding 4 of the converter 2 a Voltage is induced which - after rectification in bridge 13 - immediately closes transistor 1 again open so that a control in the desired sense would not be possible.

To prevent this, the secondary winding of the converter is terminated by a resistor 12 and a counter voltage is introduced into the feedback circuit, which in the exemplary embodiment is tapped at a variable resistor 16. A set of rectifiers connected to AC terminals 19, 20 is used to generate the counter voltage 18 with smoothing choke 17. The counter voltage is dimensioned so large that the voltage

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the drop in the magnetizing current at the ohmic resistor 12 is always smaller than the counter voltage and therefore cannot open the transistor 1 unintentionally.

In addition, the Graetz bridge can also be equipped with a series connection of ohmic resistance 14 and Throttle 15 be bridged. The purpose of the ohmic resistor 14 is for the counter voltage at the variable resistor 16 to create a bypass next to Graetz Bridge 13. As is well known, every transistor has some leakage current, d. In other words, in the blocking state, current flows from the collector via the base and the control circuit to the emitter. This leakage current can lead to a resistance in the control circuit produce large voltage drop that the transistor is opened inadvertently. To avoid this, the voltage drop must be compensated for by a counter voltage. The existing Serve counter voltage at the variable resistor 16, it only has to be ensured that it is not is blocked by the Graetz bridge 13, which has the opposite forward direction.

The choke 15 supports the counter voltage insofar as they maintain their current flow and therefore a voltage in introduces the feedback circuit that seeks to block the transistor.

To control a consumer direct current, the consumer is in series with the transistor in the Direct current branch of the Graetz bridge laid. A corresponding embodiment is shown schematically in FIG shown. It refers to the speed control of a DC motor, being the switch acts as a regulator. The individual circuit elements, insofar as they correspond to those of FIG. 1, provided with the same reference numerals. A counter-tension 16, which is only indicated here, provides as in the device of Fig. 1 for the fact that the voltage drop of the magnetizing current across the resistor 12 cannot accidentally open the transistor.

With the motor 11, a tachometer generator 22 is mechanically coupled, which in a known manner The voltage proportional to the speed is generated as an actual variable. It is compared with the nominal voltage, and the control deviation influences the tax rate 21. If necessary, feedback (e.g. for current limitation), Fault values etc. can be switched to the tax rate. In parallel with the ohmic-inductive A zero anode 23 is arranged on the load.

As already mentioned earlier, the transistor 1 may at most carry the maximum permissible collector current. The collector current results directly from the quotient of the mains voltage peak value and the impedance in the entire circuit. If the maximum current determined in this way would exceed the permissible collector current, the current must be limited by suitable means. This can be done in a number of ways. For example, the mains voltage can be reduced with the aid of a transformer, in particular an autotransformer. Furthermore, as shown in FIG. 2, a choke 24 can be arranged in the alternating current circuit. The same purpose is fulfilled by an ohmic series resistor in the direct current circuit, ie in series with the transistor, although active losses occur in the series resistor. In addition, a choke L can be connected in series with the direct current consumer, so that the collector current can only increase proportionally to the time. The transistor must then be closed in good time by a current limiting circuit so that the maximum collector current is not exceeded. Which of these measures is used depends largely on the data of the transistor and the load.

Claims (11)

Patent claims: 1. Electronic switch for consumer circuits fed from an alternating current network with a transistor which is supercritically fed back via a saturation-free current transformer in such a way that the transformation ratio of the current transformer is at most equal to the current amplification factor of the transistor, according to patent application S 57104 VIII a / 21a ¹ , characterized in that that the transistor is in the direct current branch of a Graetz bridge (6) and that the feedback current supplied by the converter is rectified by a Graetz bridge (13). 2. Electronic switch according to claim 1, characterized in that the secondary side of the Converter is completed by an ohmic resistor (12). 3. Electronic switch according to claims 1 and 2, characterized in that in An opposing voltage is introduced into the feedback circuit, which is greater than the voltage drop of the The magnetizing current of the transducer at the terminating resistor (12) is. 4. Electronic switch according to claims 1 to 3, characterized in that the Graetz bridge for the feedback current is bridged with a resistor (14) so that the Counter voltage prevents the transistor from opening as a result of the leakage current. 5. Electronic switch according to claims 1 to 4, characterized in that with The bridging resistor has a throttle (15) in series, which supports the counter voltage. 6. Electronic switch according to claims 1 to 5, characterized in that the Mains voltage is selected so high that the maximum permissible collector current of the transistor is not is exceeded. 7. Electronic switch according to claims 1 to 5, characterized in that im Circuit an impedance to limit the collector current is arranged. 8. Electronic switch according to claim 7, characterized by a throttle in the AC circuit. 9. Electronic switch according to claim 7, characterized by a resistor in the direct current circuit. 10. Electronic switch according to claim 7, characterized by a choke in the direct current circuit and the use of a current limiter circuit. 11. Use of the electronic switch according to one of claims 1 to 10 as a controller, in particular for speed control of DC motors. Considered publications:
German interpretative document No. 1 063 208. 1 sheet of drawings © 009 549/298 6.60