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.
Ratio measurements of a transformer are of extreme importance for several reasons, such as:
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.
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.
Are you calibrating your Transformer Turns Ratio Test Set often enough?
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