A transformer turns ratio test confirms ratio accuracy of a transformer. The test ensures the correct ratio of both primary turns and secondary turns. It can also help to identify issues related to tap-changer performance, shorted turns, incorrect winding connections, and open windings. Due to the many benefits a transformer turns ratio test can reap, it is crucial and also within your best interest to have your transformer tested frequently.
WHY RATIO MEASUREMENTS OF TRANSFORMERS ARE IMPORTANT
Ratio measurements of a transformer are of extreme importance for several reasons, such as:
- Quality verification
- Validation of design specifications
- Assessment of possible damage
- Establishment of transformer condition and condition trends
Transformer turns ratio tests should be completed on a frequent basis to ensure the accuracy of a transformer. During testing if ratio results differ from the expected target values, the likeliness of a defect or error is high. Untargeted results could indicate a defect in winding or a tap-changer.
STYLE VARITIES OF TRANSFORMER TURNS RATIO TEST SETS
Before testing a transformer, it’s important to observe which transformer test set is necessary. Types of transformer turns ratio test sets vary in style and test connections; however, all test sets consist of at least two high leads and two low leads. Different styles of transformer turns ratio tests sets include:
Single-phase models are designed to measure the turns ratio and exciting current windings in power transformers. These models are primarily used for testing single-phase power with low ratios; however they can be used to test three-phased transformers. If used to measure three-phase transformers each phase has to be tested separately.
Three-phase models are designed to measure the turns ratio of power, instrument and distribution transformers in a manufacturing setting. Unlike the singe-phase model, the three-phase model can test high ratios.