The Single-Phase TTR® Transformer Turns Ratio Test Set measures the turns ratio and exciting current of windings in power, potential and current transformers. Deviations in turns ratio readings indicate problems in one or both windings or the magnetic core circuit.

The single-phase model is available in either hand-cranked or line-operated versions and measures highly sensitive turns ratios of up to 129.99:1 with accuracy of ±0.1%. An optional auxilary transformer extends the ratio range to 329.99:1.

The TTR set operates on the principle that the voltage ratio of the transformer at no load is practically equal to the true turns ratio.

The major source of error in a transformer is a primary impedance drop due to magnetizing current, which is kept to a minimum by excitation at a fraction of rated voltage. By employing a design that meets both of these conditions along with the use of a null balance system, the turns ratio of a transformer can be determined accurately.

The single phase models are primarily used for testing single-phase power and distribution transformers, for low-ratio readings up to 129.99:1, or up to 329.99:1 with an auxiliary transformer. They also can be used to test three-phase transformers by connecting and testing each phase separately.