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.


SLA Series Three-Phase Monitoring Relay

SLA Series Three-Phase Monitoring Relay

The 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.

SLB Series Phase Unbalance Monitor

SLB Series Phase Unbalance Monitor

The SLB Series is designed to protect three-phase equipment against Phase Unbalance, Phase Loss, and Phase Reversal conditions.

SLC Series Phase Unbalance and Loss Monitor

SLC Series Phase Unbalance and Loss Monitor

The SLC Series is designed to protect 3-phase equipment against Phase Unbalance and Phase Loss conditions.

SLD Series Phase & Under Voltage Monitor

SLD Series Phase & Under Voltage Monitor

The SLD Series is designed to protect 3-phase equipment against Phase Unbalance, Phase Loss, Under Voltage and Phase Reversal conditions.

SLE Series Phase Monitor

SLE Series Phase Monitor

The SLE Series is designed to protect three-phase equipment against Phase Unbalance, Phase Loss, and Under Voltage.

SLH Series Phase Loss, Under Voltage and Phase Sequence Monitor/Relay

SLH Series Phase Loss, Under Voltage and Phase Sequence Monitor/Relay

  The SLH Series is designed to protect equipment against PHASE LOSS (single phasing), UNDER VOLTAGE (brown outs), and PHASE REVERSAL (improper sequence).  The SLH is unique in that it has a field-adjustable hysteresis.

SLJ Series Phase Sequence & Under Voltage Monitor

SLJ Series Phase Sequence & Under Voltage Monitor

The 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).

PRT Phase Rotation Tester

PRT Phase Rotation Tester

The PRT-100 is a hand-held tester that takes the guesswork out of connecting a three-phase motor.

SLU-0200 Series Universal Phase Monitoring Relay

SLU-0200 Series Universal Phase Monitoring Relay

The SLU-0200 Phase Monitor Relays (3-Phase Monitors) provide cost-effective protection against premature equipment failure or downtime caused by voltage faults or untimely outages on 3-Phase systems (Wye or Delta). The SLU-0200 comes complete with “Rapid Cycle Lockout.”

SLM Series Microprocessor-based Three-Phase Monitor

SLM Series Microprocessor-based Three-Phase Monitor

The SLM series is a microprocessor based 3 phase monitor. This device protects 3 phase equipment from under voltage, over voltage, phase loss, phase reversal, phase unbalance, phase shift and frequency shift.

PRA Series Phase Sequence Monitor

PRA Series Phase Sequence Monitor

For applications where only the phase sequence is critical, consider the PRA Series Phase Sequence Monitor.  

SLU-600 Universal Phase Monitoring Relay

SLU-600 Universal Phase Monitoring Relay

The SLU-600 series is a family of universal phase monitoring relays, designed to provide cost-effective protection from premature equipment failure or downtime caused by voltage faults or untimely outages on three-phase systems (Delta and Wye) up to 700 VAC.

SLU-100 Series Universal Phase Monitoring Relay

SLU-100 Series Universal Phase Monitoring Relay

The 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).