DE2634742A1 - STATIC CONTROL TRANSFORMER - Google Patents

Description

78/76 Me / Approx

BBC Aktiengesellschaft Brown, Boveri & Cie., Baden (Switzerland)

Static regulating transformer

The invention relates to a static regulating transformer for the generation of variable voltages and / or currents, based on the constant applied to the primary winding Alternating voltages.

The patent (Pat.Anm. P25 32 321 describes a static potentiometer in which a package of 8 resistors with dual graded values is connected to an alternating voltage via a triac each (Fig. 1)

Dual counter controlled in such a way that the total resistance value in

G
2 = 256 steps from a maximum value (only 1 triac open)

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drops to a minimum value (all triaes open). By external Any intermediate value can be preset for the 8-digit binary number at the output of the counter. Under use of the variable resistor, a variable current or a variable voltage can be generated. However, must here the disadvantage must be accepted that the output power because of the heat generated in the variable resistor is limited.

The invention is based on the object of eliminating this disadvantage of the circuit arrangement already proposed and to provide a device which enables a substantially lossless generation of a variable voltage. this is achieved in that with a regulating transformer mentioned at the beginning the secondary winding is divided into a number (n) of series-connected partial windings and each between two partial windings are arranged first electronic switch that a dual counter is provided by a pulse generator Counting pulses of a certain frequency are fed to the respective count at η parallel outputs corresponding binary code combinations generated that the partial windings have dual graded nominal voltages that each Output of the dual counter is connected to the control electrode of a first electronic switch, which is on

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the partial winding with the one corresponding to the said dual counter output dual graded nominal voltage immediately follows, and that second electronic connected in series with one another Switch each bridge the series connection of a partial winding and the subsequent first electronic switch and can be controlled by the outputs of the dual counter so that when any first electronic switch is opened the corresponding second electronic switch is closed, while when the first electronic switch is closed Switch the associated second electronic switch are always open.

Thus, according to the invention, the individual resistors of the arrangement already proposed are replaced by partial coils of the secondary winding of a transformer in such a way that a variable voltage can now be generated without loss, except for the internal transformer losses. This arrangement is therefore suitable for greater powers.

The basic circuit diagram of the regulating transformer according to the invention is shown in FIG. 2. The transformer 1 has, for example, 8 secondary windings with dual graded nominal voltages, for example W ₁ = IV, W ₂ = 2V, W, = 4V >> W ₁₁ = 8V, W ₅ = 16V, etc. On Counter 2, the pulses from a pulse generator, not shown

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A certain frequency are supplied, controls the first electronic switch A. to Ag and the second electronic switch B ₁ to Β «in such a way that a voltage appears at the terminals a and b, which can vary in 256 steps from IV to 256 V. Code combinations corresponding to the count appear at parallel outputs of counter 2, and outputs 1 to 8 are connected to the control inputs of the first switch A, which are connected downstream of the partial windings W that are homologous to the counter outputs, and also to the negated control inputs of the associated second switch B connected. As can be seen, the partial windings W are connected in series with first electronic switches A located between two windings, while the second electronic switches B each bridge the associated series connection of W and A. In addition, the second switches B are all connected in series with one another. The first and second electronic switches are preferably designed as triacs.

When binary zeros are present on all control electrodes of switches A and B, the first switches A are all closed, the second switches B, in which the zero signal is inverted at the control input, are all open. When a binary ^w l ^{n is applied} to a pair of switches A, B , the switching state of the two switches is reversed.

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The mode of action is now on for some code combinations Counter output explained:

a) Counter output 1000 0000 = 1

The switch pair A, B. reverses its switching state, ie A ₁ opens and B. closes. For all other switch pairs, the Α switches remain closed, the B switches open. The windings W_ to Wg are removed from the circuit a - b without being short-circuited. Total voltage Vb = ^1V = ^W l

b) Counter output 0100 0000 = 2

The switch pair Ap, B ₂ reverses its switching state, all other pairs remain.

U. = 2V = 2W _O
starting at 2

c) counter output 1100 0000 = 3

The switch _{pairs A 1} , B. and A_, B_ reverse the switching state, all other pairs remain. Vb = 3V = W _{1 +} W ₂

d) Counter output 0010 0000 = 4

The switch pair 3 reverses the switching state, all others Couples stay.

U. = 4V s W, from 3

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χ) Counter output 1111 1111 = 256

All switch pairs reverse the switching state Vb = 256 V = W ₁

Any binary value can also be specified externally at the counter output. In this way, a certain voltage can ü. can be selected. Further, it is suitably ₅ to switch the switch couples with the zero crossing of I. to synchronize (otherwise unpleasant communication overvoltages will occur at the terminals).

The voltage drop across the switches (which, as mentioned, are preferably triacs) can be compensated for with an additional winding 3. Since 8 switches are always connected in series regardless of the switching state of the secondary windings, a compensation voltage of 8 times the switch loss voltage is correct at any point in time. The compensation winding 3 is designed accordingly.

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Claims (5)

-f- 78/76 Claims 1 / Static regulating transformer for the generation of variable voltages and / or currents, based on the constant alternating voltage applied to the primary winding, characterized in that the secondary winding of the transformer is divided into a number (n) of series-connected partial windings (W, ... W -) is divided and between two partial windings (Wy) first electronic switches (A _v ) are arranged that a dual counter (2) is provided to which counting pulses of a certain frequency are supplied by a pulse generator and which corresponds to the respective count at η parallel outputs binary code combinations generated that the partial windings (Wy) have dual graded nominal voltages, that each output of the dual counter (2) is connected to the control electrode of a first electronic switch (A ^), which is connected to the partial winding (Wy) with the said dual counter -Output corresponding dual graded nominal voltage immediately follows, and that with each other in R e series-connected second electronic switch (B _v ) each bridge the series connection of a partial winding (Wy) and the subsequent first electronic switch (A ^) and are controlled by the outputs of the dual counter (2) so that 709882/0592 ORIQlNAL INSPECTED when any first electronic switch (Ay) is opened, the corresponding second electronic switch (BjO is closed while in the closed state the first electronic switch (Ay) the associated second electronic switch (By) are always open. 2. Static regulating transformer according to claim 1, characterized in that that the first (Ay) and second (B ^) electronic Switches are triacs that are controlled in a complementary manner in pairs by the output of the counter (2). 3. Static regulating transformer according to claim 1 or 2, characterized in that any dual values at the output of the counter (2) can be specified externally, with which a certain voltage (U.) can be preselected. el "" D 4. Static regulating transformer according to claims 2 and 3 »thereby characterized in that the switching of the triac pairs is synchronized with the zero crossing of the secondary current (I,) will. 5. Static regulating transformer according to claims 2-4, characterized marked that to compensate for the voltage drop across the triacs at the end of the entire secondary winding 709882 / 059.2 - # - 78/76 chain an additional winding (3) is provided, which is designed so that the compensation voltage is equal to η times the value of the triac loss voltage. BBC Public Company Brown, Boveri & Cie. 709882/0592