Omron K8DT-PH1CN — Phase-Seq / Phase-Loss Relay
SKU: K8DT-PH1CNUSD 32.00
K8DT 17.5 mm 3-phase reverse-phase + phase-loss monitoring relay on 200-480 VAC, SPDT 5 A relay output, Push-In Plus terminals.
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Product Overview
The Omron K8DT-PH1CN is a slim three-phase monitoring relay for the two most common motor-damaging supply faults: a swapped phase wiring hookup that reverses direction, and a lost phase after a fuse or contactor issue. It measures the phase-to-phase voltage on a 3-wire 3-phase 200-480 VAC supply, watching for sequence error or collapse to zero. On a fault it drops a single SPDT contact (5 A at 250 VAC) within 0.1 s. It is the standard pick to protect a 3-phase motor or compressor feed where a wrong phase sequence would drive the shaft backwards.
Where it fits in the K8D family
The K8D line is split by function and supply. K8DT-PH monitors reverse-phase + phase-loss on 200-480 VAC (this unit). K8DT-PM2 is the 3-phase voltage + reverse-phase + phase-loss relay at 380-480 VAC. K8DS-PU2 monitors undervoltage. K8DS-PZ monitors voltage imbalance. Pick the K8DT-PH1CN when the only job is to catch a swapped phase or a blown fuse. Pick the K8DS-PM2 when undervoltage and overvoltage tripping are also needed. Pick the K8DT-PM1 for a 200-240 VAC three-phase voltage relay.
Push-In Plus vs screw terminals
The CN suffix on this unit is the Push-In Plus terminal block. Use stranded wire with ferrules (AWG24 to AWG16, 0.25 to 1.5 mm^2), insert directly, and the contact closes without a screwdriver. Strip 8 mm of insulation. The TN sibling uses M3 screws for sites that already have ferruled wire and want the service pattern. Both terminal styles share the same body and DIN-rail mount.
Before ordering
Confirm the supply is a true 3-wire 3-phase (no neutral needed). Select the right unit for the supply voltage: 200-480 VAC covers most global industrial supplies. Wire 3-phase to the three input terminals. Mount on a DIN track (PFP-100N / PFP-50N) or with M4 screws. Allow the relay to drop any motor contactor or drive enable on its own fault trip.
Key Features
- K8DT-PH family 3-phase reverse-phase + phase-loss relay
- 3-phase 200-480 VAC input, 3-wire (no neutral)
- Input burden ~2.6 VA at rated voltage
- Reverse-phase trip 0.1 s +/- 0.05 s
- Phase-loss trip 0.1 s max on 100 % -> 0 % rapid collapse
- SPDT contact output 5 A at 250 VAC / 30 VDC resistive
- Auxiliary 24 VDC 50 mA transistor output
- Automatic reset, PWR green + OUT yellow LEDs
- Phase-loss detect level 80 % +/- 10 % of rated input
- 17.5 x 90 x 90 mm slim DIN-rail body, Push-In Plus terminals
- SKU: K8DT-PH1CN
- Series: K8DT-PH three-phase monitor
- I/O: 3 I/O
Best-Fit Applications
- Reverse-phase guard on an HVAC or air-compressor feed
- Phase-loss trip on a pump starter for agricultural irrigation
- Pre-charge interlock on a 3-phase battery or DC bus cabinet
- Motor protector on a conveyor or mixer main feed
- Direction-watch on a lift station or hoist controller
Buying Checklist
- Confirm the supply is 3-phase 200-480 VAC with no neutral needed.
- Choose K8DT-PM1 when monitoring 200-240 VAC three-phase voltage.
- Choose K8DT-PM2 when undervoltage and overvoltage are also needed.
- Choose K8DS-PU2 when the job is undervoltage-only protection.
- Choose K8DS-PH1 for the previous-generation 17.5 mm body with screw terminals.
- Confirm the 24 VDC transistor output is wired to a PLC input for fault logging.
Technical Specifications
| Series | K8DT-PH three-phase monitor |
|---|---|
| Function | Reverse-phase + phase-loss detection (3-wire) |
| Rated Input | 3-phase 200-480 VAC |
| Input Burden | ~2.6 VA at rated voltage |
| Operating Time | Reverse-phase 0.1 s +/- 0.05 s; phase-loss 0.1 s max on rapid collapse |
| Reset | Automatic reset |
| Output | SPDT relay 5 A at 250 VAC / 30 VDC + 24 VDC 50 mA transistor |
| Indicators | PWR green LED, OUT yellow LED |
| Mounting | DIN track (PFP-100N / PFP-50N) or M4 screws |
| Dimensions | 17.5 x 90 x 90 mm (W x D x H) |
| Operating Temperature | -20 to 60 degC (no icing, no condensation) |
| Degree of Protection | IP20 (terminals) |
Resources & Downloads
FAQ for K8DT-PH1CN
What is the difference between K8DT-PH and K8DS-PH?
Both are reverse-phase + phase-loss relays. The K8DT is the current generation 17.5 mm slim body with the same trip thresholds (0.1 s reverse-phase, 0.1 s phase-loss) and adds the Push-In Plus terminal option. The K8DS-PH is the previous-generation line with screw terminals. Pick K8DT-PH1CN for new designs; K8DS-PH1 for direct screw-terminal service of existing panels.
Does the K8DT-PH1CN monitor undervoltage?
No. The K8DT-PH only watches phase sequence and the loss of any phase to near-zero on the same 200-480 VAC range. For undervoltage protection on 380-480 VAC use K8DS-PU2. For voltage + reverse-phase + phase-loss on 380-480 VAC use K8DS-PM2. For voltage imbalance on three-phase supplies use K8DS-PZ.
How do I wire the Push-In Plus terminals?
Strip 8 mm of insulation and use stranded wire with a ferrule sized to AWG24-16 (0.25 to 1.5 mm^2). Insert directly into the terminal opening; the clamp closes without a screwdriver. Solid wire and ferruled stranded wire both fit. Up to 50 insertions per terminal. Remove with a flat-blade screwdriver (Omron XW4Z-00B or a 0.4 x 2.5 mm tip).
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