LPRA/2 Under Voltage and Asymmetry Monitoring Relay

  • Under voltage and asymmetry monitoring
  • Selectable nominals for popular 3-wire or 4-wire supply voltages
  • Detects incorrect phase sequence, phase and neutral loss
  • Adjustable Trip level and Time delay
  • 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 asymmetry/unbalance within the set limits. If any of these conditions are not met, the relay will de-energise.

  • Monitoring function: Under voltage/asymmetry
  • Monitored supply voltages: (3-wire) 380V, 400V or 415VAC/(4-wire) 220V, 230V or 240VAC (Order Code: 99-4202)
  • Asymmetry trip level: 2 – 20%
  • Hysteresis: ≈2%
  • Time delay: 0.2 – 10s
  • Output: DPDT 5A @ 250V (AC1)
  • Dimensions(mm): W:17.5 x H:89 x D:66.5
Distributors Stock Code Link
RS Components 1356186 (400VAC) Go to product
Farnell 2677819 (400VAC) Go to product

Typical applications include:

  • Industrial pumping systems
  • Three-phase compressor installations
  • Conveyor systems
  • Motor control centres

Key benefits:

  • Helps reduce exposure to supply unbalance — Adjustable phase-asymmetry monitoring can release the equipment control permissive when the measured voltage unbalance exceeds the selected limit.
  • Avoids phase-order restrictions — The relay operates irrespective of phase sequence, allowing voltage supervision where phase order is immaterial or checked separately.
  • 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.
  • Allows the response to suit the equipment — The asymmetry threshold and fault delay can be adjusted to suit the supply-unbalance sensitivity and response requirements of the connected equipment.
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