PBD Series 3-Phase Sequence & Voltage Band Monitor Relays The PBD Series offers protection to three-phase sequence sensitive equipment that is required to operate between two voltage limits. All three phases are monitored individually for a pre-selected UNDER and OVER VOLTAGE limit, with adjustable release delay. With normal operating voltages applied in the proper ABC sequence, the internal relay will energize (PICK-UP). When the voltages on any or all phases fall outside the preset Over/Under trip points for longer than the Adjustable Release delay, the relay will de-energize (DROPOUT). When line conditions return to normal, the PBD Series Monitor automatically resets and the internal relay energizes. Both Delta and Wye systems may be monitored. In Wye systems, connections to neutral are not required. The LED fault indicators aid in set up and system troubleshooting, and glow on fault condition. The LED indicators have an immediate response to voltage conditions and operate independently of the relay. In a phase reversal condition the LED responds to voltage conditions but the relay will NOT energize. The Adjustable Release Delay is provided to ignore momentary voltage fluctuations that cause nuisance tripping. The HYSTERESIS in each unit provides a differential of 4 percent between the PICK-UP and DROP-OUT trip points. The PBD Series is UL Listed under UL File Number E55826.