A small-sized voltage stabilizer without switching condensers in comparison with widely known analogue provides smaller mass parameters due to the application of a minimum quantity of semiconductor devices and more effective current loading of the device and a network as a whole.
It is necessary to recognize as a lack of many stabilizers comparative complexity and big mass parameters connection with the necessity of application of switching condensers.
In comparison with widely known analogues the offered voltage stabilizer  provides smaller mass parameters due to the application of a minimum quantity of semiconductor devices and more effective current loading of the device and a network as a whole. The device provides a combination of voltage adding transformer functions and functions of a compulsory locking thyristor device.
Let´s consider the stabilizer operation (Figure) the network and loading voltage are smaller than a nominal level, i.e. at Us < 220 V. It is assumed that in this case relay 6 is initially switched on and its contacts 5 shunt a primary winding of transformer 1, accordingly, the voltage at its secondary winding is also equal to zero. When thymistor 4 is off, the loading forms a series circuit with a secondary winding of transformer 2, which in this case acts as a reactor. Thus the most part of the mains voltage will be applied to a winding and loading voltage can be practically equal to zero. However it takes place only on the initial site of a mains voltage half-wave the duration of which is determined by the «breakdown» voltage of stabilitron 9
When the voltage reaches the specified level and stabilitron 9 in transformer 8 primary winding of galvanic outcome starts to conduct current, the in thymistor 7 control circuit will be increased and the latter will be on. Shunting of transformer 2 secondary winding by means of thymister 7 will result in spasmodic change of the loading instant voltage up to the level of the network Us voltage.
It is assumed that the automatic control and output voltage stabilization system functions according to the principle of output coordinate (Uс) deviation from a present value (Uy). The signal of a regulation mistage from an output of regulator 12 enters the input of pulse phase control device 11 which develops unlocking pulses for thymistor 4. The smaller the stabilizer output voltage, the smaller the phase angle of thymistor a control, the more the voltage adding which is delivered to the loading circuit by transformer 2 primary winding is connected to the mains voltage source, the e. m. being induced in the secondary winding, the phase of which due to the way of primary and secondary winding connection specified in the scheme coincides with the network voltage phase. As a result thymistor 7 is under the influence of the specified winding indirect voltage and is locked. Thymistor 7 locking out results in the fact that the loading instant voltage from the moment a up to the end of a half -cycle is determined by the sum of the mains voltage and voltage adding transformer 2 secondary winding voltage. Thus the effective value of voltage adding provided by transformer 2 during the period is in direct dependence on a regulation mistake and it provides a stabilization effect of an output voltage. Thymistor 4 at the considered half-cycle is switched off naturally after the mains voltage reduction and then the current in transformer 2 primary winding is decreased up to zero. It is necessary to note that the repeated switching of thymistor 7 and shunting of the specified transformer secondary winding is possible only when thymistor 4 is switched off. During the following mains voltage the circuit will function similarly.
If the network voltage exceeds the nominal level Us > 220 V relay 6 will be switched and deliver the mains voltage to the transformer 1 primary winding via contacts 5. The winding of the specified transformer are connected in such way that the induced in the secondary winding e.m.f. is opposite to the network voltage in phase, therefore the resulting loading voltage will be determined by the difference of the mains voltage and the e.m.f. of stepping down transformer 1 secondary winding. If the output voltage reduction is excessive, the stabilization system with stepping up transformer 2 begins its functions.
A small-sized stabilized without switching condensers
Thus, the considered stabilizer provides constant maintenance of output voltage at the mains voltage fluctuations in both nominal value directions employing a minimum quantity of semiconductor devices. Additional thymistor 7 provides shunting of a stepping up transformer winding at the moments when voltage adding is not necessary and it promotes more effective current device loading and loading of a network as a whole.
Combing voltage adding transformer functions and thyristors artificial switching device functions allowed us to exclude switching condensers, it being an advantage of the technical decision
1. The patent № 2128393 Russian federation. A voltage stabilizer / L.T. Magazinnik, J.J. Magazinnik // 27.03.1999.