How To Test Power Transformer

Power transformers can be tested using a multimeter. 

The test method is as follows:

(1) Measurement of DC resistance of transformer windings.

Transformer winding DC resistance is very small, use the multimeter's R × 1Ω block detection to determine whether the transformer windings have short circuit or open circuit condition. Under normal circumstances, the DC resistance of the primary winding of the power transformer (buck type) is several tens of ohms to hundreds of ohms, and the secondary dc resistance is more than a few ohms to several ohms. Relative to the transformer, the DC resistance of the transformer winding is generally very small, only a few ohms

(2) Testing of transformer insulation performance.

The insulation performance of the transformer can be easily measured using the R×10k block of the analog multimeter. Measure the resistance values between the transformer core and the primary, primary and secondary, core and each secondary, static shielding layer and the primary and secondary windings respectively. The pointer of the multimeter should be fixed or resistance at infinity. Should be greater than 100mΩ, otherwise the transformer insulation performance is poor

(3) The detection of the no-load voltage of the power transformer.

Connect the 220V mains of the power transformer's primary and use the multimeter's AC voltage to measure the no-load voltage value of each winding in order to meet the required value. The allowable error range is generally ≤±10% for the high voltage winding and <±5% for the low voltage winding. The difference between the voltages of two symmetrical windings with a center tap should be ≤±2%