Inductive Load
Load on Secondary of Transformer
Transformer have inrush current on start up. Special Tyristor Power Controller are required. REVO CL up to 700A is normally used for 1PH loads. Over this current we recommend the Multidrive family up to a current of 2700A. REVO E and Multidrive is used for three phase transformer. Close examination of the transformer application needs to be made a the typical inrush current, when switched on. This over-current will have the result to damage Fuses or Thyristor.
CD AppNotes Eng Application Notes – Rev2 (576,9 KB)
To avoid this peak current two techniques can be used:
Phase angle firing with soft start and current limit. This type of firing can be used with all types of loads.
- Normal resistance.
- Cold resistance (Example: Kanthall Super elements)
- Transformer coupled with normal or cold resistance.
- With cold resistance use I feed-back.
Burst firing using the Delay Triggering (DT) technique. To avoid magnetic circuit saturation, the thyristor unit will switch OFF when the load voltage is negative and switch ON again when positive. The unit also has an adjustable delay on voltage zero crossing. In this way it is possible to switch ON when current is zero. This Firing technique can only be used with normal resistance, where its resistive value remains constant with temperature variations.