SUBSTANCE: flywheel of alternate moment of inertia comprises a shaft where a three-arm bracket is rigidly fixed and a central gear wheel is installed bymeans of bearings. The bracket ends are fitted by coaxially set flywheel segments providing for the accumulation of kinematic energy and toothed segments rigidly connected to the flywheel segments. The toothed segments are geared with the central gear wheel. Potential energy accumulator is made as a spring coiled around the shaft in the cavity formed by the shaft and the central gear wheel. The spring ends are connected to the central gear wheel and the three-arm bracket.