<p>This paper describes the use of a current transformer to monitor and control the reactive power of an induction motor. The current transformer is placed between the induction motor stator windings and the main winding. The result is a voltage signal due to the main and stray magnetic currents generated in the induction motor stator winding. The study of dynamic properties of the signal received from the measuring instrument, taking into account the interaction of various specific quantities, differential equations describing the transient processes in the primary and secondary sections of the transformer signal change, signal transmission elements and due to the difficulty in formation, is conducted on the basis of the developed mathematical apparatus - the graph model and its analytical expressions. The main element of the current transformer is the measuring coil, i.e. sensitive element. Depending on the number of slots of the induction motor stator the sensing element is made in the form of two- or three-ring. The measuring accuracy, reliability and sensitivity are increased compared to an independent measuring device. The sensor rings are connected independently or in series. When measuring circuits are connected in series, the output voltage value doubles. Influence of asynchronous motor on primary stator current at independent and series connection of gauge rings is obtained by means of dynamic descriptions.</p> <p> </p> <p> </p>