Circuit arrangement for energy economy

In a circuit arrangement for economizing the use of electrical energy in a drive which includes an induction motor and a clutch-brake unit particularly for sewing machines, in which the windings of the induction motor are such that the motor speed remains virtually constant in a stable speed range under under normal service conditions, and in which the clutch-brake unit serves to control the drive output speed so that the motor operates in an alternation of load phases and no-load phases, the improvement wherein switches (7, 8) are included in the current paths of said windings (1,2) to reduce the current flow through said windings (1,2) by a predetermined amount, and wherein the arrangement includes modulation circuit means (9) operatively cooperable with said switches (7,8), said modulation circuit means (9) containing a delay element (10) which is triggered when the mains voltage is applied, and an impulse prolongation element (13) which receives a switching signal when said clutch is engaged, wherein at least one of said switches (7 or 8) comprises a Triac (41) or thyristor (43), and wherein a phase shifter circuit (19) cooperates with at least one of said switches (7 or 8), whereby at least one of said switches (7 or 8) is controlled so as to minimize the current loss in the circuit arrangement via said at least one switch (7 or 8).