Control process for operating a parallel-resonant circuit inverter that supplies an inductive charge, as well as the parallel-resonant circuit inverter operated by this method

A method for operating a parallel-resonant circuit inverter with a rectifier, a thyristor DC/AC converter connected to this rectifier and operated with controllable frequency, which converter feeds the parallel-resonant circuit containing the inductive load, comprising the steps of

• measuring of DC/AC converter voltage U, and the thyristor extinction time t.sub.L during the operation,
• controlling the DC/AC converter frequency .omega. to maintain the DC/AC converter voltage U constant at an operating value U.sub.B, for a constant direct current I.sub.g = I.sub.go, in a first control range characterized by a low resonant-circuit damping, and
• controlling the direct current I.sub.g for the purpose of maintaining the DC/AC voltage constant at its operating value U.sub.B, in the case of a constant thyristor extinction time t.sub.L = t.sub.L0, in a second control range characterized by a high damping, as well as by transition from the first to the second control range, if t.sub.L becomes equal to t.sub.L0 in the case of increasing resonant-circuit damping, and transition from the second to the first control range, if I.sub.g become equal to I.sub.go in the case of decreasing damping.