The SPD480 determines phase rotations on secondary potential transformers. Easy to operate - connect one lead to each phase. Large alligator clips for easy connection to cables and bus bars. Operates properly on variable frequency drives. Does not give false readings by pulsed waveforms. Verify proper rotation on feeder extensions. Determine phase rotation on secondary potential transformers. Voltage range: 110V to 480V 3 phase. Maximum voltage input: 480V. Frequency response: 40Hz to 70Hz. Maximum voltage input time ratings: 480V 4 minutes, 450V 4 minutes, 220V 30 minutes, 110V Continuous. Test lead insulation rating: 1000V. Fusing: 500mA, 50kA interrupting rating. Rotating disk indicates phase rotation. Size: 6" length x 3" width x 1-19/32" height. ROHS Compliant.