Transformer have an inrush current on start up. For this kind of application is required special SCR Power Controller.
For 1PH loads we suggest you REVO C 1PH or REVEX 1PH for small current. REVO C 3PH 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.
To avoid the peak current we suggest you to use the following techniques:
1) Phase angle firing with soft start and current limit. This type of firing can be used with all types of loads.
Cold resistance (Example: Kanthall Super elements)
Transformer coupled with normal or cold resistance.
With cold resistance use I feed-back.
2) 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.