Phase protection relay - FKV-24F | TENSE

The FKV series phase protection relays are designed to protect three-phase equipment, especially motors, against faults related to incorrect voltage value, asymmetry, phase failure or incorrect phase sequence. The FKV-24F operates over a wide range of 180-500 VAC and has a fixed asymmetry of 11%.

It ensures reliable operation of equipment with high demands on power accuracy and protects it from thermal and mechanical damage.

Functions and working principle

Voltage asymmetry (11 %)

• Monitors the difference between phase voltages.

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

• When the difference drops by 5 V, the relay evaluates the condition as normal and resumes the output after a delay period.

Phase sequence check

• Correct phase sequence → OUT LED is lit, output is active (NO switched on).

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

High voltage protection (U>)

• If the voltage exceeds 500 V, the high voltage indication is activated.

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

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

Low voltage protection (U<)

• If the voltage drops below 180 V, the low voltage indication is activated.

• If the condition does not end during the error delay, the output will shut down.

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

Status indications

• 5 LEDs inform about:

  • relay status (OUT)

  • high voltage (U>)

  • low voltage (U<)

  • phase sequence

  • asymmetry / fault

Main features

• Wide operating voltage range: 180-500 VAC

• Fixed asymmetry: 11%

• Protection against:

  • Low voltage

  • High voltage

  • asymmetry

  • phase sequence errors

  • phase failure

• No need for a neutral conductor

• Fast response to fault conditions (approx. 1 s)

• LED indication of all functions

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

Technical parameters