The relays of the SUR353Z series are designed to monitor the voltage of three-phase AC systems. Neutral conductor connection is not required, hence the relays are suitable for 3AC and 3NAC systems. External supply voltage is not required.

• Undervoltage monitoring orr 3AC / 3NAC systems
• Without external supply voltage
• Adjustable response value 0.7…0.95 x Un
• Nominal system voltages
  3AC 100 V, 230 V, 400 V, 415 V, 500 V, 690 V

• Monitoring of the power supply of motors and electrical installations
• Monitoring of loads
• Switching on and switching off at a certain voltage level
• Monitoring of stand-by and emergency supply systems
• Supply voltage monitoring of portable loads