Phase / Voltage Monitors

Three Phase Monitors

Three-phase monitors from the ATC Diversified Electronics division of Marsh Bellofram offer cost-effective, high-reliability industrial motor and equipment protection. Models are designed to accommodate a variety of voltage ranges and enclosure types, all designed for easy installation, effectively providing early warning of voltage faults, a major contributor to premature equipment failure.

DLA Series

Voltage Band MonitorsThe Marsh Bellofram DLA series is a family of three-phase industrial monitors, providing high-reliability protection for motors and equipment within an easy-to-install, DIN-rail mounted enclosure. The series is available in two unique models, covering voltage ranges up to 480 VAC, and providing effective monitoring three-phase mains for under voltage, phase loss and phase sequence conditions, with an adjustable time delay feature to help prevent nuisance trips

PRA Series

Single Phase For applications where only the phase sequence is critical, consider the PRA Series Phase Sequence Monitor. When the phase sequence is correct (ABC) and the operating voltage is present on all phases, the relay will energize and the green LED indicator will glow. If the phases are in reverse rotation, the relay will not energize and the red LED indicator will glow. Please note that the PRA Series Relay will not detect phase loss while the motor is turning.

SLU-100 Universal Phase Monitoring Relay

Type 110 photoThe Marsh Bellofram SLU-100 series is a family of universal monitor relays, designed to provide cost-effective protection against premature equipment failure or downtime caused by voltage faults or untimely outages on three-phase systems (Delta and Wye), such as those typically found in motor control centers or other critical motor and pump monitoring applications.

SLU-600 Universal Phase Monitoring Relay

Type 110 photoThe Marsh Bellofram SLU-600 series is a family of universal phase monitoring relays, designed to provide cost-effective protection against premature equipment failure or downtime caused by voltage faults or untimely outages on three-phase systems (Delta and Wye) up to 700 VAC, such as those typically found in motor control centers or other critical motor and pump monitoring applications. The SLU-600 series unique rapid cycling feature prevents motors from cycling due to load-induced line fault conditions.

SLA Series Three-Phase Monitoring Relay

Type 110 photoThe Marsh Bellofram SLA series is a family of three-phase universal phase monitoring relays, designed to provide cost-effective protection against from phase loss, under voltage, and phase reversal conditions that can contribute to premature motor or equipment failure and downtime on three-phase systems (Delta and Wye), such as those typically found in motor control centers or other critical motor and pump monitoring applications.

SLB Series

Type 110 photoThe SLB Series is designed to protect three-phase equipment against Phase Unbalance, Phase Loss, and Phase Reversal conditions. With normal operating voltages in the proper ABC sequence and the 120 VAC control voltage applied, the internal relay will energize (PICK-UP). When any combination of Phase Unbalance exceeding the preset value or Phase Loss or Phase Reversal occurs for longer than the preset drop out time, the output relay will de-energize (DROP-OUT). If the control voltage is removed, the relay will de-energize.

SLC Series

Type 110 photoThe SLC Series is designed to protect 3-phase equipment against Phase Unbalance and Phase Loss conditions. With normal operating voltages applied to all three phases, the internal relay will remain de-energized (DROPPED-OUT). When a Phase Loss or Phase Unbalance exceeding the pre-selected trip point occurs, the relay will energize (PICK-UP). The SLC series is typically used in conjunction with a shunt trip breaker. Both Delta and Wye systems may be monitored. In Wye systems, connections to neutral are not required.

SLD Series

Type 110 photoThe SLD Series is designed to protect 3-phase equipment against Phase Unbalance, Phase Loss, Under Voltage and Phase Reversal conditions. With normal operating voltage present on all three phases in the proper phase sequence, the internal relay will energize (PICK-UP). When an incorrect phase sequence or phase loss occurs or the three-phase line voltages fall outside the preset unbalance or under voltage settings, the internal relay will de-energize (DROP-OUT). When all conditions return to normal, the relay will reset.

SLE Series

Type 110 photoThe SLE Series is designed to protect three-phase equipment against Phase Unbalance, Phase Loss, and Under Voltage. With normal operating voltage present on all three phases, the internal relay will energize (PICK-UP). When a phase loss occurs or the voltages fall outside the preset unbalance or under voltage settings, the internal relay will de-energize (DROP-OUT). The relay automatically resets when the line conditions return to normal.

SLH Series

Type 110 photoThe SLH is unique in that it has a field-adjustable hysteresis. The voltage setting is adjusted to the desired pick-up point indicated by the dial setting. Then, the hysteresis adjustment is set to the desired percentage to achieve the preferred drop-out point. When models up to 300 VAC are set at 0%, they will pick-up and drop-out at the same point, when set at 10%, the drop-out will be an average of the phase-to-phase voltages 10% below the dial setting pick-up point. Models over 300 VAC are adjustable from 0% to 15%.

SLJ Series

Type 110 photoThe SLJ Series has a built-in Delay-on-Make Time Delay. The SLJ continuously monitors the three phase lines for adverse conditions such as PHASE LOSS (single phasing), UNDER VOLTAGE (brown outs), and PHASE REVERSAL (improper sequence). When any of these conditions occur, the internal relay will de-energize (DROP-OUT). When the fault is corrected, the field adjustable delay-on-make delay begins. Upon completion of the time delay, the internal relay will energize (PICK-UP). Any subsequent interruptions will reset the delay period.

SLM Series

Type 110 photoThe SLJ Series has a built-in Delay-on-Makeis. The SLJ is a microprocessor based 3-phase monitor. Protects 3-phase equipment against: under Voltage, over voltage, phase loss, phase reversal, phase unbalance, phase shift and frequency shift. Models are available up to 690 VAC with automatic or manual reset.