3-phase undervoltage and phase-sequence phase-loss relay

The K8DS-PU is the simplified 3-phase monitoring relay, 3-wire circuits within one unit. It can monitor undervoltages, phase sequence and phase loss.

  • Greater resistance to inverter noise
  • One SPDT output relay, 5 A at 250 VAC (resistive load)
  • World-wide power specifications supported by one unit (Set with a rotary switch)
  • Relay status can be monitored using LED indicator
Specifications & ordering info

Ordering information

Rated input

Order code

3-phase 3-wire mode

200, 220, 230, 240 VAC


3-phase 3-wire mode

380, 400, 415, 480 VAC



Ambient operating temperature

−20 to 60°C (with no condensation or icing)

Storage temperature

−25 to 65°C (with no condensation or icing)


2,000 m max.

Voltage fluctuation range (UNDER)

Undervoltage 30 to 25% of rated input voltage

Input frequency

50/60 Hz (AC power supply)

Output relays
(1× SPDT, normally closed operation)

Resistive load

5 A at 250 VAC or at 30 VDC

Maximum contact voltage

250 VAC or 30 VDC

Maximum contact current

5 A

Maximum switching capacity

1,250 VA, 150 W

Mechanical life

10,000,000 operations

Electrical life

50,000 operations at 5 A, 250 VAC

Degree of protection

Terminal section: IP20

Case material

PC UL94 V-0


Approx. 65 g

Rated input voltage


3-phase, 3-wire mode: 200, 220, 230, 240 VAC


3-phase, 3-wire mode: 380, 400, 415, 480 VAC

Operation (overvoltage or undervoltage)

Operating value setting range

Undervoltage = −30% to 25% of maximum rated input voltage

Operating value

100% operation at set value

Reset (HYS.)


5% of operating value (fixed)

Resetting method

Automatic reset

Operating time (T)


0.1 to 30 s


0.1 s ±0.5 s


0.1 s ±0.05 s

Power ON lock (LOCK)

0.1 s ±0.5 s

Overload capacity

Continuous input: 500 V

Repeat accuracy

Operating value

±0.5% full scale (at 25°C and an ambient humidity of 65% at the rated power supply voltage, 50/60 Hz sine wave input)

Operating time

±50 ms (at 25°C and 65% humidity, rated power supply voltage)


Power (PWR): Green LED, relay output (RY): Yellow LED, UNDER: Red

Applicable standards

Conforming standards

EN 60947-5-1
Installation environment (pollution level 2, installation category III)


EN 60947-5-1

Safety standards

UL 508 (Recognition), Korean Radio Waves Act (Act 10564), CSA and CCC

Size in mm (H × W × D)

80 × 17.5 × 74

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