Phase protection relay – FKV-24F | TENSE

Phase protection relays of the FKV series are designed to protect three-phase devices, especially motors, from faults related to incorrect voltage values, asymmetry, phase loss, or incorrect phase sequence. The FKV-24F model operates in a wide range of 180–500 V AC and has a fixed asymmetry of 11 %.

Ensures reliable operation of devices with high power supply accuracy requirements and protects them from thermal and mechanical damage.

Functions and operating principle

Voltage asymmetry (11 %)

• Monitors difference between phase voltages.

• If asymmetry exceeds 11 %, relay switches off output and opens NO/COM contacts after approx. 1 s.

• When difference decreases by 5 V, relay considers state normal and reactivates output after delay.

Phase sequence control

• Correct phase sequence → OUT LED lights, output is active (NO closed).

• Incorrect phase sequence → LED turns off and output enters fault state.

Overvoltage protection (U>)

• If voltage exceeds 500 V, overvoltage indication activates.

• If the condition lasts longer than 2 s, the relay switches off the output.

• After voltage drops 5 V below U>, the relay starts delay countdown and then resumes operation.

Undervoltage protection (U<)

• If voltage drops below 180 V, undervoltage indication activates.

• If the condition persists during the fault delay, the output switches off.

• After voltage rises 5 V above U<, the relay reactivates the output after a time delay.

Status indicators

• 5 LEDs indicate:

  • relay status (OUT)

  • overvoltage (U>)

  • undervoltage (U<)

  • phase sequence

  • asymmetry / fault

Main features

• Wide operating voltage range: 180–500 V AC

• Fixed asymmetry: 11 %

• Protection against:

  • undervoltage

  • overvoltage

  • asymmetry

  • incorrect phase sequence

  • phase loss

• No need for neutral conductor

• Fast fault response (approx. 1 s)

• LED signaling of all functions

• Suitable for motors, compressors, pumps, and other three-phase loads

Technical parameters