To observe the appearance of transformer has obvious unusual phenomena. Such as coil lead break or not. The insulation materials has scorch marks or not. The stickers meet the engineering requirements or not.
Using multimeter test iron core and primary, the primary and secondary, the resistance of secondary winding separately. The multimeter need to point ∞. Otherwise the insulation performance of the transformer is not good and there maybe leakage.
Make the multimeter at R*1. If the resistance value of a winding is infinite that the winding has short circuit.
The primary lead and secondary lead of the power transformer are drawn from both sides and the primary lead must be double-skin insulated wire. The online leather is UL certified and heat and pressure resistant on the line.
Put the multimeter in ac 500MA frequency series into primary winding. When the plug of the primary winding is inserted, the current value displayed by the multimeter is the no-load static current value. The larger the transformer is, the larger the static current will be. If it’s too much .It shows that there is a short circuit inside the transformer.
Low-power transformer is allowed to heat up to 40-50 degrees. If the insulation material quality is good, the temperature rising can be increased.
No obvious rust on the iron shell and iron core and no obvious defects in the intimate framework of the shell. The lead wire is firmly connected with insulated and non-destructive. The exposed part has no obvious oxidation. Iron core silicon steel sheet arranged neatly, strong. Abnormal noise and vibration are not allowed after electrification.