Synchronous motors which are over-excited in the branched radial network, to which a large number of high-voltage asynchronous motors and transformer stations are connected, can operate as synchronous compensators. By adjusting the excitation current on the rotor, synchronous motors can be supplied by appropriate active power P ≈ Pr = const. from the network, and send reactive power back to the network Q = f (Ie) and thus improve the power factor. The adjustment of synchronous motor excitation current depends on the load, and it is necessary to analyze the load by measuring electrical quantities of a synchronous motor with variable load. This paper presents an analysis of synchronous motor loads, using fuzzy c-clustering method. A classification of load groups has been designed and the maximum load for certain working conditions has been determined as well as currents of excitation circuit in the given conditions.