ODES Motor Phase‑Sequence Relay Application Guide

TonyZhang
Oct 4
2 min read

Three‑phase motors are exposed to two high‑impact risks during maintenance and temporary hookups: incorrect phase sequence (reverse rotation) and phase loss (overcurrent, overheating, potential burnout). A protection‑grade phase‑sequence relay prevents these conditions by verifying positive sequence (ABC) and supervising phase presence before permissive is issued.

1) Input Wiring — Three Equivalent Methods

Principle: parallel the motor/bus phases A, B, C—in the same rotation order as the site—to relay terminals 1, 2, 3 (often labeled L1, L2, L3). Any one of the following preserves positive sequence:

A→1, B→2, C→3
A→2, B→3, C→1
A→3, B→1, C→2

If two phases are swapped, the relay indicates wrong sequence and drives the outputs to a safe state; correct by swapping any two input phases.

2) Indication & Contacts — Read the State at a Glance

Front‑panel LEDs and output contacts identify the operating condition:

Normal (correct sequence, all phases present) – LEDs: RUN ON, ACT ON – Contacts: 11–14 and 21–24 closed; 11–12 and 21–22 open → permissive to downstream control
Wrong sequence (A/B/C order abnormal) – LEDs: RUN ON, ACT OFF – Contacts return to safe: 11–12 and 21–22 closed; 11–14 and 21–24 open
Phase loss (any phase absent/low) – LEDs indicate fault; contacts revert to safe state (same as wrong sequence)

This combination minimizes meter‑by‑meter probing and accelerates fault location.

3) Operating Modes — WORK vs TEST

A red selector on the front panel provides two modes:

WORK: participates in sequence/phase‑loss supervision and drives outputs per logic.
TEST: supervision bypassed; outputs do not operate—used for maintenance, commissioning, and demonstrations.

4) Commissioning Checklist

Wiring verification: apply one of the positive‑sequence mappings above; confirm normal indication (RUN/ACT ON).
Functional tests: simulate two faults—swap any two phases (wrong sequence) and open one phase (phase loss)—confirm LED and contact states.
Timing settings: apply time‑delayed supervision to ride through brief transients and avoid nuisance operations in frequent‑start drives (cranes, fans, pumps).

5) Integration Notes

Wire the relay output in series with the contactor permissive or feed it to PLC interlock logic to block start or command a controlled stop on fault.
Use the LED state as a first‑line diagnostic before deeper inspection of fuses, terminals, and feeders.

6) Selection Highlights

Narrow DIN‑rail housing (22.5 mm), IP20 touch‑safe, V0 enclosure for dense panels.
Wide input window: 187–528 VAC, 50/60 Hz auto‑sensing.
Adjustable pickup/reset and delays for coordinated permissive/blocking logic.

Conclusion

A phase‑sequence relay provides deterministic prevention of reverse rotation and single‑phasing damage. With clear indication, fail‑safe contact logic, and practical WORK/TEST modes, engineers gain faster commissioning, safer operation, and higher availability.

Need help mapping permissives or tuning delays for cranes, pumps, or compressors?

Email: tonyzhang@odes.com.cn

or visit: https://www.odes-electric.com/

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