Factors to select a power transformer.

To Select the Right power Transformer, First Determine the following things:

• Three Phase or Single Phase ,according to load
• Primary voltage, which is the available voltage
• Secondary voltage required by load equipment
• Frequency (in Hz)
• KVA load  with possible future increases factored in 0.20
• Is the transformer to be used indoors or outdoors?
• Is the transformer to be floor or wall-mounted?
• Is an auto transformer or a double-wound transformer required?
• Insulation Type (Liquid-Filled or Dry Type)
• Low-Loss Core Material
• Regulation
• Voltage Taps
• Cooling system
• Temperature Class

The manufacturers of transformers recommend that the connected wattage not exceed 90% of the Transformer's rated wattage. For example, don't connect more than 450 watts to a 500 watt transformer.

Nominal Data of a power transformer:

Description	Unit	Data
Rating Voltages	kV	11/0.4
Power rating	KVA	1000
On Load /Off Load Tapping	kV	03 Position
Coupling	-	Star/Star
Vector Group	-	Yyn0
Frequency	Hz	50
Maximum Oil Temperature	K	40
Hot Spot Winding Temperature	K	65
Temperature Class		A
No Load Loss	kW	1
Full Load Loss	kW	3
No-Load Current	%	0.4