Winding resistance measurements in transformers are important for the following purposes:
1. Calculations of the I2 R component of conductor losses.
2. Calculation of winding temperature at the end of a temperature test cycle.
3. As a base for assessing possible damage in the field.
Transformers are subject to vibration. Problems or faults occur due to poor design, assembly, handling, poor environments, overloading or poor maintenance. Measuring the resistance of the windings assures that the connections are correct and the resistance measurements indicate that there are no severe mismatches or opens.
Many transformers have taps built into them. These taps allow ratio to be increased or decreased by fractions of a percent. Any of the ratio changes involve a mechanical movement of a contact from one position to another. These tap changes will also be checked during a winding resistance test.
If you are looking for a winding resistance test set, check out the testers from Raytech
The Raytech WR14 is a battery or line-operated, field-portable instrument designed specifically to measure the dc resistance of all types of magnetic windings safely and accurately.
The revolutionary charge and discharge circuits of the Raytech WR50-12 give you the power to measure resistance of highest Inductivities in shortest time. Including the world unique demagnetizing function.