Single or double phase transformers are used on energy systems either as security - isolation type transformer or  step up -down transformer, in some cases step-up and step down transformers can be produces as auto transformer for reducing the price.     
•    Nominal Power        
•    Isolation type or auto type       
•    Input-output voltage and current values according to duty factor      
•    Galvanic isolation       
•    Input - Output voltage steps        
•    Input-output connection materials        
•    Isolation class       
•    Metal enclosure and ventilation      
•    Mounting type ( horizontal - vertical ) ... Etc
GUVEN-IS determines these technical specifications by communicating directly to the customer before designing process in order to avoid any problem.  When every detail is clear a sample transformer is produced and tested by GUVEN-IS and submitted to the customer for the final approving before the ordering.