Phase sequence and phase failure sensor, with adjustable lower and upper voltage threshold CKF-318 CKF-318-TRMS

Phase Sequence and Loss Detector – Reliable Motor Protection

This microprocessor-based phase sequence and loss detector, model CKF-318, is designed to protect three-phase 400V electric motors (without a neutral wire). The device monitors key network parameters, providing protection against various anomalies that could damage the motor or disrupt its operation. This is particularly important in industrial applications and in buildings where power supply reliability is critical.

The CKF-318 sensor offers comprehensive protection, reacting to:

• voltage asymmetry between phases – prevents overloads and overheating of the motor.
• complete phase loss – immediately shuts down the motor, protecting it from serious damage.
• symmetric voltage drop in three phases – ensures stable motor operation even with reduced supply voltage.
• change in phase sequence – prevents incorrect motor rotation, which can lead to damage or inefficient operation.
• exceeding the upper voltage threshold (>480V) and lower voltage threshold (<320V) – protects the motor from excessive or insufficient supply voltage.

Thanks to the use of TrueRMS technology, the sensor provides accurate voltage measurement even in networks with harmonic disturbances, guaranteeing reliable operation in harsh industrial conditions.

Functionality and Signaling

The CKF-318 sensor has two changeover contacts (2 x NO/NC) with a maximum load current of 6A each, allowing integration with various control and protection systems. Mounting on a TH35 rail simplifies installation and servicing. Intuitive signaling with LEDs informs about the device's operating status:

• Green LED [R]:
  • Solid – network parameters correct, contact closed.
  • Flashing – countdown for restart delay.
• Red LED [U]:
  • Solid – voltage asymmetry or voltage below 320V.
  • Flashing ×1/s – incorrect phase sequence.
  • Flashing ×3/s – voltage above 480V.

Adjustable setpoint thresholds and time delays allow precise adaptation of the sensor to specific application requirements and minimize the risk of false alarms. Compatibility with generators increases the versatility of the device. 3x400V power supply ensures compatibility with most standard electrical installations. Width 18 mm (1 module) allows for efficient use of space in the switchgear cabinet.