Proceedings of the Tomsk Polytechnic Institute named after S. M. Kirov

Volume 262, 1973

150 kW DC Voltage Regulator-Stabilizer with Natural Current Limiting in the Load Circuit

A. V. Kobzev, E. G. Zavatskii, N. A. Kuchin, G. A. Shadrin

(Presented by the Scientific and Technical Seminar of the NII AEM)

In the laboratory of magnetic-valve converters of the NII AEM, a 150 kW converter has been developed with natural current limiting in the load circuit. The power regulating element is implemented on three saturable reactors with combined windings (DNSI), controlled by a pulsed method [1], connected in series with the primary windings of the matching transformer STR. The functional diagram of the regulator-stabilizer is shown in Fig. 1.

Fig. 1.

The external characteristics, which have a steeply falling character, are ensured by the natural properties of the DNSI. This makes it possible to reliably protect the power supply from short circuits and overloads. The DNSI also makes it possible to increase the efficiency and reduce the consumption of active materials.

In order to obtain the greatest effect, it is necessary to apply the control-voltage pulses at the moments of current minima in the bias circuit, coinciding with the passage of the load current through zero [2]. To satisfy this condition, current sensors are used. The signal of the current transformer (TT), proportional to the load current,

through the step-up transformer Tr1 (Fig. 2a) is applied to the bases of transistors T1, T2 of the synchronizer. The time diagrams explaining its operation are shown in Fig. 2b.

At the moment when transistors T1 and T2 are turned off, rectangular pulses are formed at the output; along their trailing edge the operation of the intermediate semiconductor amplifier (IPA) is controlled. When the load current is small, the signal of the secondary winding

a)

b)

Fig. 2

of Tr1 is insufficient to control transistors T1 and T2; therefore the initial starting of the synchronizer is carried out by the voltage from a separate winding of transformer Tr2. When the load current increases to the required value, the relay circuit transfers contact relay R1, thereby connecting the winding of Tr1 and carrying out synchronization by the load current.

In the converter, stabilization of each phase of the output voltage and stabilization of the voltage across the load are performed. The circuit

The feedback circuit is shown in Fig. 3. The algebraic sum of the output, reference, phase, and bias voltages is applied through diode D1 and winding I of comparator I to resistor \(R1\). When the voltage of the sawtooth-voltage generator (SVG) \(E_{\mathrm{p}}(t)\) is greater than the voltage drop across \(R1\), diode D2 is open and current flows through winding II of the comparator. In this case the comparator generates voltage pulses at its natural frequency. When the output or phase voltage changes, the voltage drop across resistor \(R1\) will change. This will cause a change in the duration of the pulses at the output of the switching element SE, i.e., the magnetizing current of the DCSI will change. The value of the bias voltage determines the limiting width of the magnetizing pulses. By adjusting \(E_{\mathrm{op}}\), the current-limiting set point is changed.

Current limiting in the proposed converter is characterized by high speed, and current peaks are limited both under a static and under a sudden short circuit; therefore, no additional protective elements need be introduced.

Fig. 3

The regulator-stabilizer described is competitive in all parameters with other known converters and can be recommended for wide application in systems with technologically unavoidable overloads and short circuits of the output circuit.

REFERENCES

1. V. P. Obrusnik, A. V. Kobzev. Method of pulse control. Author’s certificate No. 245842, class 21a² 18/08. Bulletin of Inventions, No. 20, 1969.

2. A. V. Kobzev. Development and investigation of pulse-magnetized ferromagnetic devices. Candidate dissertation, Tomsk, 1971.