The Vanguard TRF-100 Automatic Three Phase TTR is a microprocessor-based, automatic, three phase, transformer turns-ratio tester.

A lightweight, portable unit designed for testing transformers at utility power substations, the TRF-100 determines the transformer turns-ratio using the IEEE C57.12.90 measurement method.

The transformer turns-ratio (ranging from 0.8 to 50,000) is determined by precisely measuring the voltages across the unloaded transformer windings. To ensure accuracy, the TRF-100’s measuring circuitry self-calibrates before each measurement. It requires neither adjustment nor temperature compensation. The TRF-100’s turns-ratio measurement accuracy is 0.1% or better.