Testing a transformer with an ohm meter can provide valuable insight into its overall condition and performance. One of the most important measurements to take is the transformer DC resistance, which is also known as the winding resistance.
To begin testing the transformer, disconnect the unit from any power source. Next, locate the ohm meter and set it to the appropriate range for the transformer's expected resistance reading. This will depend on the size and type of transformer being tested.
Once the ohm meter is set up, connect its leads to the transformer terminals that correspond to the desired resistance measurement. For DC resistance testing, this usually means connecting the leads to the primary and secondary winding terminals, but refer to the transformer's manual for specific instructions.
With the ohm meter leads connected, take a reading of the transformer's resistance and compare it to the manufacturer's specifications. If the reading is significantly lower or higher than the specified range, this could indicate a problem with the transformer's windings or internal connections. In this case, further testing may be necessary to diagnose and rectify the issue.
It's worth noting that transformer resistance measurements can vary depending on the ambient temperature of the unit. For this reason, it's important to record the temperature and take multiple measurements over time to get an accurate understanding of the transformer's resistance.
Testing a transformer with an ohm meter can be a valuable tool for ensuring its proper function and diagnosing issues before they lead to larger problems. Be sure to consult with the transformer's manual and any other relevant resources before proceeding with testing, and exercise appropriate caution and safety practices. Dc resistance test of transformer winding is an essential test item after transformer handover, overhaul and tap-changer change. By measuring the DC resistance of the transformer winding, you can check the welding or connection quality of the lead, whether the winding is short or open between turns, and whether the tap changer contact is good.