In this monograph, the creation of today's perfect techniques and the growth of the economy are inextricably linked to the increase in energy consumption, the use of digital technologies is required in the assessment of the symmetrical magnitude and parameters of the reactive power of the asynchronous motor. The high accuracy, reliability, and compactness of the current transformers used in the assessment of the symmetrical values of the reactive power of the asynchronous motor widely used in production, the ability to perform non-contact measurement process, provide standardized and controllable output information expansion is one of the important tasks. It is important to implement various modeling methods and to develop and put into practice new, compact, single-shaped structures of primary signal converters based on them in the assessment of asynchronous motor reactive power.