Omron K8DS-PM2 — 3-Phase Voltage Relay, 380-480 VAC
SKU: K8DS-PM2USD 12.50
K8DS series 17.5 mm relay for 3-phase under/over-voltage, reverse-phase and phase-loss, 380-480 VAC, 1 × SPDT 5 A output.
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Product Overview
The Omron K8DS-PM2 is a 17.5 mm-wide single-function monitoring relay for three-phase power. It watches the incoming supply and trips on reverse-phase, phase loss, undervoltage, or overvoltage on a 380-480 VAC three-wire supply (rotary switch for 380, 400, 415, 480). The SPDT output drops within 0.1 s of the fault — fast enough to keep a 3-phase motor from spinning the wrong way on first power-up or burning out on a single phase. It is a voltage-detection type, so no current transformers are needed. Wire the three phases to the input terminals and the motor contactor coil through the SPDT contact. It is the standard pick on European and Asian 400 V panels where brownouts, overvoltage, wrong rotation, or single-phasing need to be shut off before damage occurs.
Where it fits in the K8DS lineup
The K8DS family splits by monitored function. K8DS-PH1 is reverse-phase and phase-loss only. K8DS-PM2 adds three-phase voltage monitoring at 380-480 VAC, and K8DS-PM1 does the same at 200-240 VAC. K8DS-PU2 is three-phase undervoltage only. K8DS-PZ2 adds voltage imbalance plus reverse and loss. Pick the K8DS-PM2 when three-phase voltage, rotation, and loss all need to be checked on a 400 V-class supply. Pick K8DS-PM1 instead on a 200 V supply. Pick K8DS-PH1 when voltage monitoring is not needed.
Why this and not the K8AK-PM
The K8AK-PM1 / K8AK-PM2 do the same job in the older K8AK form factor. The K8DS is the modern replacement: half the width (17.5 mm vs 22.5 mm), better immunity to inverter noise, and a faster decision on reverse-phase and phase-loss. New panels should standardize on the K8DS line for spare-parts commonality.
Before ordering
Wire the three phases to L1, L2, L3 — there is no neutral terminal because phase-to-phase voltage is what is monitored. Set the rotary switch to the matching nominal voltage (380, 400, 415, or 480 VAC). Mount the unit on DIN rail (PFP-100N or PFP-50N). Put the SPDT contact into the motor contactor holding-coil circuit so a trip drops the contactor out. Confirm the LED behavior: PWR (green) on when supply is OK, RY (yellow) off when the relay is energized (NC operation — opens on trip).
Key Features
- 3-phase voltage, reverse-phase and phase-loss monitoring
- Rated input 380/400/415/480 VAC, 3-phase 3-wire (rotary switch)
- Voltage-detection method, no CT required
- 0.1 s reverse-phase / phase-loss operation
- 1 × SPDT contact, AC250 V / DC30 V 5 A resistive
- Improved inverter-noise immunity
- PWR (green) and RY (yellow) status LEDs
- 17.5 mm DIN-rail housing, PFP-100N / PFP-50N rail
- SKU: K8DS-PM2
- Series: K8DS three-phase voltage monitoring relay
- I/O: 3 I/O
Best-Fit Applications
- European/Asian 400 V three-phase supply protection for motors and pumps
- Line-side monitoring upstream of a 400 V variable-frequency drive cabinet
- Reverse-rotation guard on conveyors, mixers, and extruders in plants
- Phase-presence check on three-phase compressors in chilled-water plants
- Spare replacement for legacy APR-S phase relays on older panels
Buying Checklist
- Choose K8DS-PM2 for full 3-phase voltage + rotation + loss on 380-480 VAC.
- Choose K8DS-PM1 for the same monitoring on a 200-240 VAC three-wire supply.
- Choose K8DS-PH1 when voltage monitoring is not needed and only rotation / loss matter.
- Choose K8DS-PU2 for undervoltage only at 380-480 VAC.
- Choose K8DS-PZ2 when voltage imbalance is also a concern.
- Confirm the rotary-switch setting (380 / 400 / 415 / 480 VAC) matches the supply.
Technical Specifications
| Series | K8DS three-phase voltage monitoring relay |
|---|---|
| Function | 3-phase voltage (under/over), reverse-phase and phase-loss |
| Rated Input | 3-phase 380/400/415/480 VAC, 3-wire (rotary switch) |
| Input Burden | Approx. 2.7 VA at 400 VAC |
| Operation Time | Reverse-phase / phase-loss: 0.1 s ± 0.05 s; voltage: 0.1 to 30 s |
| Reset Method | Automatic reset (manual reset via power cycle) |
| Output | 1 × SPDT (1c), NC operation (opens on trip) |
| Contact Rating | AC250 V 5 A resistive / DC30 V 5 A resistive |
| Indicators | PWR (green) power / RY (yellow) relay status |
| Mounting | DIN rail (PFP-100N / PFP-50N) or M4 panel screw |
| Operating Temperature | -20 to +60 °C |
| Operating Humidity | 25 to 85 % RH |
Resources & Downloads
FAQ for K8DS-PM2
What is the difference between K8DS-PM2 and K8DS-PH1?
K8DS-PH1 monitors reverse-phase and phase-loss only. K8DS-PM2 adds three-phase undervoltage and overvoltage on a 380-480 VAC supply. Pick PH1 when the cabinet is already on a UPS and only the rotation / phase-presence check is needed; pick PM2 when brownouts and spikes on a 400 V-class supply also need to be caught.
Does the K8DS-PM2 need a neutral connection?
No. It is a three-wire voltage-detection relay — only the three phases (L1, L2, L3) connect to the input. The relay measures phase-to-phase voltage, not phase-to-neutral, so it works on delta and ungrounded-wye supplies where a neutral is not present at the relay.
How do I set the K8DS-PM2 for 380 V / 400 V / 415 V / 480 V?
The rotary switch on the front selects the nominal rated input voltage: 380, 400, 415, or 480 VAC. Set it to the closest match before applying power. The trip thresholds are derived from this setting, so a switch set to 400 V on a 415 V supply will under-detect. Cycle power after changing the switch so the new threshold takes effect.
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