Nowadays, with the wide automation of production processes and the introduction of automatic control systems, the requirements for the creation of contactless electric devices have substantially increased. The development of power semiconductor electronics allows the solution of complex technical problems aimed at improving the efficiency of electrical devices. The leading role in this direction is given to optoelectronic devices and thyristor devices, which provide contactless switching processes and galvanic isolation, and have improved transient and frequency characteristics The article deals with the creation of compact, reliable, highspeed optoelectronic contactless voltage relays with an extended service life, combining a sensitive system and a powerful actuator having a sinusoidal shape of the voltage curve at the load. Theoretical, experimental studies and the principle of operation of an optoelectronic contactless voltage relay with time delay are given.

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Work it is devoted to research of autoparametrical fluctuations at a frequency of the third subharmonica in nonlinear electric chains by two nonlinear elements. Conditions and a zone of steady excitement of a subharmonica of the third order, and also critical parameters the subharmonicas of the third providing steady excitement an order are defined.

The article discusses the research issues and methods of analysis of semiconductor circuits used in electronic circuits of contactless switching devices, provides analytical, graphic and numerical methods for the analysis of nonlinear semiconductor resistive circuits. The approximations of the Volt-Ampere characteristics (VACh) of semiconductor elements and the solution of the differential equations of state of electrical circuits by a numerical method using a computer are given. Diode, thyristor semiconductor nonlinear resistive circuits with active and inductive loads are considered. In the analysis of steady-state modes and transient processes, numerical methods for solving differential equations of states by the Euler method were used.