The paper deals with problems connected with the single-phase operation of an induction motor possessing a three-phase winding in the stator and an additional condenser. Simulation calculations have been realized and they have shown that the pulsating torques of great amplitudes have appeared during the single-phase work of the induction motor. The mechanical pulsations generate vibration and noise. The new conception of the choice of the optimum value of the condenser capacitance has been presented. The condenser ought to ensure both the great mechanical power of the motor and decrease of vibration and noise. Besides the mechanical power and amplitude of the pulsation torque, values of many other, important electrical parameters have been simultaneously analysed, for example: power losses in windings resistances, the constant component of the motor torque, the power factor, the efficiency, currents and voltages connected with the phase windings, the electric active and reactive power, the supply current flowing from the single-phase feeding network, the voltage and the current of the condenser.