Difference between 3-phase PARACON (thyristor + diode element) and (thyristor + thyristor element)
With normal heater control, temperature can be controlled with either a thyristor + diode element or a thyristor + thyristor element.
In the case of transformer primary control, when a sudden power fluctuation, power failure, load fluctuation, load disconnection, etc. occur, the biasing phenomenon of the transformer occurs because the thyristor + diode element controls only one side of the sine wave. It is easy to do, and direct current may flow to the PARACON and transformer, causing damage.
At that point, the thyristor + thyristor element controls both sides of the sine wave, and since it has a symmetrical shape, the magnetic bias phenomenon of the transformer does not occur. In addition, the thyristor + thyristor element does not generate even when harmonics are generated, making it easier to take measures against harmonics.