Omron K8DS-PH1 — 3-Phase Phase Relay, 200-480 VAC
SKU: K8DS-PH1USD 11.00
K8DS series 17.5 mm DIN-rail relay for 3-phase reverse-phase and phase-loss protection, 200-480 VAC, 1 × SPDT 5 A output, automatic reset.
1-Year Warranty
Full manufacturer warranty
Global Shipping
Worldwide delivery available
Genuine Omron
100% authentic product
Ready to Ship
Usually ships within 24h
In Stock
This item is available for immediate shipment from our warehouse.
Contact for pricing, bulk discounts, and shipping
Product Overview
The Omron K8DS-PH1 is a 17.5 mm-wide single-function monitoring relay for three-phase power. It watches the incoming supply and trips when the phases are in the wrong order (reverse phase) or when one phase drops out (phase loss). The relay output drops out within 0.1 s, 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 directly to the input terminals and the motor contactor coil through the SPDT contact. It is the standard pick as a low-cost reverse-rotation guard on a conveyor, mixer, compressor, pump, or anywhere a wrong-phase event can damage the driven equipment.
Where it fits in the K8DS lineup
The K8DS family splits by what each relay monitors. K8DS-PH1 is reverse-phase and phase-loss monitoring at 200-480 VAC. K8DS-PM2 adds three-phase voltage monitoring in the 380-480 VAC range. K8DS-PU2 is three-phase undervoltage at 380-480 VAC. K8DS-PZ adds voltage imbalance plus reverse-phase and phase-loss. K8DS-PA1 is over / under voltage only. K8DS-AS is single-phase current monitoring. Pick the K8DS-PH1 when only the phase rotation and phase-presence checks are needed, especially on a 200 V-class three-phase supply where PM2/PZ/PH1 is the right range.
Why this and not the K8AK-PH
The K8AK-PH1 / K8AK-PM2 do the same job in the older K8AK form factor. The K8DS line is the modern replacement: half the width (17.5 mm vs 22.5 mm), better immunity to inverter noise, and a faster reverse-phase decision (0.1 s). New panels should standardize on the K8DS line for spares 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. Mount the unit on DIN rail (PFP-100N or PFP-50N). Set 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 reverse-phase and phase-loss monitoring
- Rated input 200-480 VAC, 3-phase 3-wire
- Voltage-detection method, no CT required
- 0.1 s reverse-phase / phase-loss operation
- 1 × SPDT contact, AC250 V / DC30 V 5 A resistive
- Automatic reset when fault clears
- PWR (green) and RY (yellow) status LEDs
- 17.5 mm DIN-rail housing, PFP-100N / PFP-50N rail
- SKU: K8DS-PH1
- Series: K8DS three-phase voltage monitoring relay
- I/O: 3 I/O
Best-Fit Applications
- Reverse-rotation guard on conveyors, mixers, and extruders in plants
- Supply monitoring for compressors and pumps in water plants
- Phase-presence check on three-phase pumps and fans running 24/7
- Line-side protection upstream of a variable-frequency drive cabinet
- Spare replacement for legacy APR-S series phase relays on old panels
Buying Checklist
- Choose K8DS-PH1 for reverse-phase + phase-loss only, on a 200-480 VAC supply.
- Choose K8DS-PM2 to also monitor three-phase voltage at 380-480 VAC.
- Choose K8DS-PU2 for three-phase undervoltage only at 380-480 VAC.
- Choose K8DS-PZ when voltage imbalance is also a concern.
- Choose K8AK-PH1 for the older 22.5 mm form factor on legacy panels.
- Confirm the supply is 200-480 VAC three-wire; no neutral is required.
Technical Specifications
| Series | K8DS three-phase voltage monitoring relay |
|---|---|
| Function | Reverse-phase and phase-loss |
| Rated Input | 3-phase 200-480 VAC, 3-wire |
| Input Burden | Approx. 2.7 VA |
| Operation Time | Reverse-phase: 0.1 s ± 0.05 s; phase-loss: 0.1 s or less |
| Reset Method | Automatic reset |
| 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-PH1
What is the difference between K8DS-PH1 and K8DS-PM2?
Both monitor three-phase supplies at 200-480 VAC, but they trip on different faults. K8DS-PH1 trips on reverse-phase and phase-loss only. K8DS-PM2 trips on those plus three-phase over / under voltage. Pick PH1 when only the rotation check matters; pick PM2 when the panel also needs overvoltage and brownout protection.
Does the K8DS-PH1 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.
What contact rating does the K8DS-PH1 carry?
The single SPDT contact is rated for AC250 V 5 A resistive or DC30 V 5 A resistive. That is enough to switch a contactor holding coil directly. For higher inrush loads or longer cable runs, put an intermediate relay (e.g., LY2N-J) downstream to keep the contact healthy.
Similar Products
Explore related Omron models often viewed alongside this product.
