Induction heating device with a setting preset controlled by the actual value

摘要

The invention relates to a parallel-tuned circuit converter for heating workpieces by means of an inductor with a controllable rectifier (1), an invertor (3) connected thereto via an intermediate circuit (2) and consisting of thyristors arranged in a bridge circuit, a parallel-tuned circuit (4) connected to the load points of the bridge circuit, a current measuring device (5) for the load current fed to the tuned circuit (4), a voltage measuring device (6) for the load voltage present on the tuned circuit and with a control unit (7) for the load current, which receives the signals of the measuring devices (5, 6) as input variable and controls the rectifier (1) as a function of desired values preset by a desired current value transmitter (9) and a desired voltage value transmitter (8), the desired voltage value of the desired voltage value transmitter (8) which is transmitted to the control unit (7) being limited to a limiting voltage, the desired current value transmitter (9) being controlled by the current measuring device (5) and having amplification elements of a kind such that the desired current value corresponds to the actual value of the load current which is changed by the amplification factor, and having attenuating elements of a kind such that the desired current value takes into consideration only those actual value changes which are below a permissible rate of change. <IMAGE>