how to test a 480 to 120 transformer?

To test a 480 to 120 transformer, first ensure safety by de-energizing the circuit. Use a multimeter to measure the primary and secondary voltages. Apply 480V to the primary side and check for 120V output on the secondary side. Additionally, inspect for any unusual sounds or overheating. Perform insulation resistance testing with a megohmmeter to ensure the windings are properly insulated. Finally, check for any signs of physical damage or corrosion.