K8AK-PH Omron Phase Failure Relay

The Omron Phase Failure Relay is a three-phase Phase-sequence Phase-loss Relay Using Voltage Detection Method. 22.5 mm (W). Two SPDT output relays

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Feature of K8AK-PH Phase-sequence Phase-loss Relay

• Greater resistance to inverter noise.

• Distinguishes between correct phases, phase sequence, and phase loss when power is turned ON.

• Supports phase loss detection when the motor is operating.

• 5 A (resistive load) at 250 VAC, DPDT x 1.

• Output status can be monitored using LED indicator.

• Ideal to prevent reverse operation of motors.


Specifications of K8AK-PH Phase-sequence Phase-loss Relay

Rated input voltage 3-phase, 200 to 480 VAC (3-wire)
Input load Approx. 4.1 VA
Operating time Phase sequence 0.1 s±0.05 s
Phase loss 0.1 s max. (when the voltage changes rapidly from 100% to 0% of rated voltage)
Reset method Automatic reset
Indicators Power (PWR): Green, Relay output (RY): Yellow
Output relays One DPDT relay (NC operation)
Output relay ratings Rated load
Resistive load
5 A at 250 VAC
5 A at 30 VDC
Minimum load: 24 VDC, 4 mA (reference values)
Mechanical life: 10 million operations min.
Electrical life:
5 A at 250 VAC or 30 VDC: 50,000 operations
3 A at 250 VAC/30 VDC:100,000 operations
1 A, cos θ = 0.4 at 250 VAC: 100,000 operations
0.2 A, L/R = 100 ms at 48 VDC: 12,000 operations
Recommended fuse: NT00-6A
Rated operating voltage (Ue)
Rated operating current (Ie)
AC-12 Ue:250VAC, Ie:5 A
AC-15 Ue:250VAC, Ie:1 A
DC-12 Ue:30VDC, Ie:5 A
DC-13 Ue:24VDC, Ie:0.9 A
DC-13 Ue:48VDC, Ie:0.2 A
DC-13 Ue:24VDC, Ie:0.05 A
Ambient operating temperature -20 to 60°C (with no condensation or icing)
Storage temperature -25 to 65°C (with no condensation or icing)
Ambient operating humidity 25% to 85% (with no condensation)
Storage humidity 25% to 85% (with no condensation)
Altitude 2,000 m max.
Terminal screw tightening torque 0.49 to 0.59 N·m
Terminal wiring method Recommended wire
Solid wire: 2.5 mm2
Twisted wires: AWG16, AWG18
Note: 1. Ferrules with insulating sleeves must be used with twisted wires.
Note: 2. Two wires can be twisted together.
Recommended ferrules
Al 1,5-8BK (for AWG16) manufactured by Phoenix Contact
Al 1-8RD (for AWG18) manufactured by Phoenix Contact
Al 0,75-8GY (for AWG18) manufactured by Phoenix Contact
Case color N1.5
Case material PC and ABS, UL 94 V-0
Weight Approx. 130 g
Mounting Mounts to DIN Track.
Dimensions 22.5 × 90 × 100 mm (W×H×D)




Allowable operating voltage range 85% to 110% of rated input voltage
Input voltage range 200 to 480 VAC
Input frequency 50/60 Hz (no presumed range)
Overload capacity Continuous 528 V
Phase loss detection level 80%±10% of rated input
Calculation Formula
= 1 – ((Highest phase-to-phase voltage – Lowest phase-to-phase voltage)/
Average three-phase phase-to-phase voltage)
Conforming standards EN 60947-5-1
Installation environment (pollution level 2, installation category III)
EMC EN 60947-5-1
Safety standards UL 508 (Recognition), Korean Radio Waves Act (Act 10564),
CSA: C22.2 No.14, CCC: GB/T 14048.5
Insulation resistance 20 MΩ min.
Between external terminals and case
Between input terminals and output terminals
Rated insulation voltage 690 V
Dielectric strength 2,000 VAC for one minute
Between external terminals and case
Between input terminals and output terminals
Rated impulse withstand voltage 6 kV
Noise immunity 1,500 V power supply terminal common/normal mode
Square-wave noise of ±1 μs/100 ns pulse width with 1-ns rise time
Vibration resistance Frequency: 10 to 55 Hz, 0.35-mm single amplitude
10 sweeps of 5 min each in X,Y, and Z directions
Shock resistance 100 m/s2, 3 times each in 6 directions along 3 axes
Degree of protection IP40 (Terminals: IP20)
Conditional short-circuit current 1,000 A