The M1PRC/S-4W from Broyce Control is a discontinued but once widely used three-phase voltage monitoring relay. It was designed to protect equipment by monitoring critical aspects of a 3-phase, 4-wire supply. Here's what it offered:

Key Features

• Monitoring Functions:
  • Under-voltage and over-voltage (window type)
  • Phase sequence detection
  • Phase loss and neutral loss
• Supply Voltage:
  • Operates on its own 230V AC 3-phase, 4-wire supply
• Trip Levels:
  • Adjustable thresholds for both under and over-voltage
• Time Delay:
  • Adjustable from 0.2 to 10 seconds to prevent false tripping
• Output Relay:
  • SPDT contact, rated at 8A  250V AC1
• Mounting:
  • Slim 17.5mm DIN rail housing