Abstract: In capacitor equipment which includes a series-connection, connected to an alternating voltage network, of two anti-parallel connected thyristors, one capacitor and one reactor, a control device is connected to the control electrode of the thyristors and arranged to ignite the thyristors alternately at times in the vicinity of the peak value of the alternating voltage. A sensing member is provided for sensing an operating magnitude in the series connection and a level-sensing member is connected to the sensing member and to the control device. The level-sensing member influences the control device to produce ignition of both thyristors of the instantaneous value of the operating magnitude falls outside a pre-determined interval.

Abstract: A controlled static convertor has terminals for connection to an alternating current source and includes controlled rectifiers and a control pulse device for delivering control signals to the rectifiers. The control pulse device includes arrangements for affecting the control angle (.alpha.) of the rectifiers and for limiting the control angle to an upper limit value. Devices are provided to render the control angle limiting arrangement inactive when the direct current of the convertor is discontinuous. The direct current of the convertor is sensed and, if this current at a time corresponding to the upper limit value of the control angle is less than a predetermined limit value, renders the control angle limiting arrangement inactive.