The TNS/SJW series three-phase high-precision automatic AC voltage stabilizer delivers reliable voltage regulation for industrial and commercial applications. Built on the foundation of single-phase TND units, it employs a three-phase independent adjustment design to ensure stable and balanced output across all phases. The unit integrates a contact auto-transformer, servo motor, and an intelligent automatic control circuit. When grid voltage fluctuates or load conditions change, the control circuit automatically drives the servo motor to adjust the carbon brush position on the auto-transformer, maintaining a constant output voltage. Designed for a three-phase four-wire (Y-shaped) input system, it offers flexible output options (three-phase three-wire or four-wire). Operation is simplified via a centralized voltmeter with a phase selector switch for line voltage monitoring, complemented by three separate ammeters for real-time phase current display, ensuring operational safety and visibility.