DISCRETE TRANSFORMER–THYRISTOR PROGRAMMABLE VOLTAGE REGULATOR

S. P. PARNIKOV, G. I. KOROLEV

(Presented by the scientific and technical seminar of the Research Institute of AEM)

In various technological processes there arises a need for programmable regulators whose output voltage represents various periodic or nonperiodic functional dependences on time. High-power programmable regulators are usually implemented with the use of movable mechanical parts and electrical contacts [1, 2], which reduces their reliability and speed of response and complicates the rapid obtaining of functions of different types.

The proposed programmable regulator (Fig. 1) has high reliability, speed of response, and flexibility in changing the program. It

Fig. 1. Programmable voltage regulator.

consists of an inverter 1, made on the primary winding of transformer 2, forming voltage-addition sections 3, isolating diodes 4, load 5, current sensor 6, and programming device 7. The windings of the voltage-addition sections (VAS) are connected in opposition with respect to the secondary winding of the transformer and, depending on the state of the controlled valves, the voltages of the VAS are either excluded from the series circuit of the load or are present in it.

The voltages of the VAS windings may be related to one another as the coefficients of a binary, ternary, or any other type of code; they may have completely arbitrary ratios, depending on the purpose of the device. The use of a code law makes it possible to obtain a large number of possible output-voltage levels with a comparatively small number of digit windings and valves.

The voltage-addition sections of the output-voltage shaper may be implemented in various versions, which are shown in Fig. 2. The same figure also indicates the possible states of the sections corresponding to the coefficients of a binary or ternary code.

Fig. 2. Variants of construction of voltage-addition sections.

Depending on the type of controlled valves used, the shaper may consist of one or two parallel branches of series-connected VAS. In the case of unidirectional valves, the branch terminals are connected to the load as in the example of Fig. 1, a; in the case of bidirectional valves, the load is connected into the diagonal of a bridge circuit, the arms of which consist of diodes when obtaining a unipolar function, or of thyristors when obtaining a bipolar function. The use of unidirectional valves increases the reliability of the device, since possible short-circuited loops are eliminated during transient modes and in the event of failures of the control signals.

Fig. 3. Timing diagrams of the programmable regulator.

The operation of the programmable regulator (Fig. 1) in forming a periodic unipolar output voltage is explained by the timing diagrams in Fig. 3, where the following are shown: \(a\)—the voltage of inverter 1, induced in the secondary and discharge windings of transformer 2; \(б\)—the output voltage across load 5; \(в\)—synchronizing pulses generated by programmable unit 7 from the signal of current sensor 6 at the instants when the current of the secondary winding passes through the zero level (an active load is taken as an example); \(г\)—the total voltage of the secondary winding and the voltage-adding branches (positive pulses are for the secondary winding with the right-hand branch, negative pulses for the secondary winding with the left-hand branch); \(д, е, ж\)—pulses for controlling the switches of the ten voltage-adding sections, respectively for the first (least significant), second, and third digits.

The waveform of the regulator output voltage is determined by the program of operation of the device and, in the example of Fig. 3, \(б\), has been chosen arbitrarily. The voltage of sections 1 and 2 is formed by the difference between the voltage of the secondary winding and all the voltages of the voltage-adding sections (VDS) of the right-hand branch (section 1) and the left-hand branch (section 2), since at this time there are no signals for turning on the shunting switches of the VDS. The first section (Fig. 3, \(г\)) is formed when current flows through the circuit: beginning of the secondary winding of transformer 2 (marked in Fig. 1 by a dot), right-hand VDS branch, load 5, left-hand decoupling diode 4, current sensor 6, end of the secondary winding of transformer 2. The second section: secondary winding, current sensor 6, right-hand decoupling diode 4, load, left-hand VDS branch, secondary winding. Thus, the current through the load flows in one direction.

At the beginning of the third section the thyristor of the least significant digit is turned on, and the voltage across the load increases by the value of the increment determined by this digit, since the previously series-connected voltageערע

the lower-order winding is excluded from the series load circuit by being shunted with a thyristor switch, while the blocking diode is closed by the voltage of its own winding, preventing a short circuit. The remaining portions of the output voltage are formed in an analogous manner; the thyristors of the corresponding DVS are turned on by pulses $d$, $e$, $zh$ (Fig. 3), and they are turned off under the action of the DVS voltage in the negative half-periods (natural commutation). By setting different pulse programs with device 7, unipolar functions of various forms can be obtained. The program can be set manually by means of a pushbutton matrix field or by coupling the shaper to a digital computer. In the latter case, direct reading of graphically specified functions from special screens is possible. Each step of the output voltage can be composed of a series of inverter pulses; therefore, the period of the output function can be varied over wide limits.

The output power of the programmable regulator can range from units of volt-amperes to tens of kilovolt-amperes while maintaining high reliability and speed of operation of the device, and the relatively high operating frequency of the inverter makes it possible to obtain small overall dimensions and weight of the regulator.

REFERENCES

1. V. I. Pribora. Calculation and design of a potentiometric programmable device. Pribory i sistemy upravleniya, 1969, No. 7.

2. V. I. Pribora, A. I. Bezrukov, E. P. Frolova. Author’s Certificate No. 153321. Byulleten izobretenii, No. 5, 1963.