Frequency converters are frequency converters which create an oscillating circuit without rotating parts via a combination of a condenser and a choke. In the case of so-called triductors, 3-fold mains frequency, and quinductors, 5-fold mains frequency, the 3-fold or 5-fold mains frequency is generated as the operating frequency direct from the mains frequency with a converter efficiency level of approx. 0.94. Modern converters have an efficiency level of 96%, and generate the required operating frequency of approx. 70 – 10,000 Hz via a rectifier.
These converters are equipped with a rectifier, which generates a 1-phase direct current from the 3-phase rotary current by means of thyristors or diodes. A direct current smoothing is incorporated between the rectifier and the inverter as an intermediate circuit. After the choke comes the adjustable inverter, which automatically generates the corresponding operating frequency in relation to the inductivity of the furnace, the capacity of the condenser bank and the power consumption. These are referred to as load-controlled converters, which are known as “A” parallel or “B” series oscillating circuit converters, depending on the condenser switching.
A: high current between furnace and condensers only
B: high current in the complete furnace circuit
