The invention relates to electronics and automatics, specifically to devices for converting alternating current energy in input into alternating current energy in output for voltage variation without intermediate conversion into direct current by static converters made on semiconductor elements with a control electrode and elements assigned for opening and closing contacts. An ac voltage regulator comprises an input low-pass filter, a series switch, a parallel switch, a choke, an output low-pass filter, an output relay. Moreover, an input relay and a parallel relay are connected. Inputs and outputs of elements are connected in a certain manner. Relays are made capable of commutation its corresponding inputs and outputs. The series switch is made capable of closure when the parallel switch being opened and capable of opening when the parallel switch being closed. A scheme of the voltage regulator allows obtaining a device that, comparing to available analogues, has minimal HWD, weight and cost with reasonably efficiency, and may be used specifically in ac stabilizers.