INDUCTIVE LOAD – SELECT YOUR LOAD CONNECTION:
PURE RESISTIVE LOAD ON SECONDARY:
Pure Resistive Elements Secondary 1PH Transformer
Pure Resistive Load Secondary 3PH Transformer
LOAD ON SECONDARY OF TRASFORMER
Transformer have an inrush current on start up. For this kind of application is required special SCR Power Controller.
Up to 700A 1PH loads we suggest you REVO CL. 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.
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.
- Normal resistance.
- 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.
This kind of heaters, MoSi2 Element ( Kanthal Super Elements TM* ), increase resistivity sharply with temperature. The value of the resistance at ambient temperature is very low and increase its value up to 10 times as a function of temperature. To don’t oversize in current the Thyristor unit it’s necessary to limit the current to the load reducing the voltage with phase angle firing and current limit. When the resistance value reach a setted value are possible two types of working method that can be selected from HMI:- Phase Angle plus current limit all the time long Or- Phase Angle plus current limit when the resistance is cold and transfering to Delayed Triggering if load is coupled with transformer. CD Automation can drive this kind of elements with REVO CL and Multidrive 1ph Units.
Select the SCR ( thyristor ) controller for Pure Resistive Elements on the Secondary of 1PH Transformer.
Transformer have inrush current on start up for this reason special SCR Power Controller are required. For 1ph load REVO CL up to 700A is normally used. Over this current we recommend the Multidrive family up to a current of 2700A. Multidrive and REVO E is used for three phase transformer.