LPRD/2 Three Phase Under Voltage Relay

  • Under voltage with restart delay
  • Selectable nominals for popular 3-wire or 4-wire supply voltages
  • Detects incorrect phase sequence, phase and neutral loss
  • Adjustable Trip level and Time delays
  • DPDT Relay output
  • 17.5mm wide, DIN Rail mount
  • UL Listed

The product monitors it’s own three-phase supply and can be set for either 3-wire or 4-wire monitoring. For the output relay to energise, all phases (and neutral – if applicable) must be present, phase sequence correct and measured phase voltages above the set trip level. If any of these conditions are not met, the relay will de-energise. An adjustable restart delay allows the user to set a period of time before the relay is allowed to re-energise.

  • Monitoring function: Under voltage
  • Monitored supply voltages: (3-wire) 380V, 400V or 415VAC/(4-wire) 220V, 230V or 240VAC
  • Under trip level: 75 – 95% of selected nominal
  • Hysteresis: ≈2%
  • Time delay: 0.2 – 10s (Restart delay: 1s – 5m)
  • Output: DPDT 5A @ 250V (AC1)
  • Dimensions(mm): W:17.5 x H:89 x D:66.5

(Order Code: 99-4208)

Distributors Stock Code Link
RS Components 1356184 (400VAC) Go to product
Farnell 2677818 (400VAC) Go to product

Typical applications include:

  • Refrigeration compressor panels
  • Booster pump installations
  • Air-handling units
  • Process cooling systems

Key benefits:

  • Helps reduce low-voltage operation — Under-voltage monitoring releases the output relay when the monitored supply falls below the operating threshold, allowing equipment to be inhibited.
  • Allows a controlled return to operation — The adjustable restart delay holds the relay de-energised after acceptable supply conditions return, giving the control circuit a deliberate recovery interval.
  • Responds to phase and neutral faults — Phase-loss detection and neutral-loss detection in the supported four-wire arrangement can release the control permissive when the incoming supply is incomplete.
  • Matches the monitored supply arrangement — Selectable nominal voltage allows the relay to be set to a supported supply, while the documented output provides an external control permissive.
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