XHYZ1668T On-Load Tap Changer Tester| Three-Phase Synchronization Analyzer The on-load tap changer is the only moving part connected to the transformer circuit, and OLTC faults are a leading cause of transformer unplanned outages. The XHYZ1668T lets plant electrical teams measure the transition waveform, transition time, instantaneous transition resistance and three-phase synchronization of transformer on-load tap changers during routine preventive maintenance, without