Designed to protect three-phase equipment from adverse voltage and/or operating conditions, the SLD Series of three-phase motor protection relays recently earned UL approval. When full line voltages are applied to the input terminals and are in proper sequence, the internal DPDT relay will pick up. When an incorrect sequence or phase loss occurs or the line voltages fall outside the unbalance or undervoltage adjustable settings, the relay will drop out. An adjustable release delay feature is provided to ignore momentary voltage fluctuations that cause nuisance tripping. Both Delta and Wye systems may be monitored.