Phase sequence and phase failure sensor CKF-B contacts: 1 CO (Changeover) contact, I=10A, 2 modules

Phase sequence and phase failure protection relay – reliable motor protection

This relay, catalog number CKF-B, is a key element in protecting three-phase powered electric motors. Its function is to monitor the presence of all phases and detect voltage asymmetry, which helps avoid motor damage and ensure its long-term operation. The device is mounted on a standard TH-35 rail and occupies 2 modules (35 mm).

Versatile application and protection

The CKF-B relay protects against the effects of phase loss or asymmetry, which can lead to overheating and damage to the motor windings. Additionally, it protects against unwanted changes in motor rotation direction in case of phase sequence changes at the input. This is particularly important in applications where the direction of rotation is critical for the proper operation of the device.

How does it work?

If an irregularity is detected – phase loss or exceeding the voltage asymmetry threshold (55V) – the relay switches off the motor with a 4-second delay. This delay prevents accidental motor shutdown due to momentary voltage drops. After the correct power supply conditions are restored, the motor will start automatically after the voltage increases by 5V above the trip value. In the event of a phase sequence change, the relay will block motor start until the correct sequence is restored.

Key features and parameters:

This relay is characterized by a supply voltage of 3 × 400 V + N, a rated current of 10 A, and has 1 x NO (normally open) separated contact. The voltage asymmetry trip value is 55 V, and the voltage hysteresis is 5 V. The shutdown delay is set to 4 seconds. The connection is made using 4.0 mm² screw terminals. The operating temperature is in the range of -25°C to +40°C, and the degree of protection is IP20. Mounting is on a TH-35 rail and occupies 2 modules (35 mm).

For installers and end-users:

The CKF-B relay is easy to install and connect thanks to the use of screw terminals. Its compact size allows installation in limited space within the switchboard. LED signaling indicates the device's operating status: a green LED indicates correct phase sequence and readiness for operation, a red LED indicates an incorrect phase sequence, and the absence of both LEDs indicates a phase failure or excessive voltage asymmetry. This facilitates diagnostics and quick problem solving. The device is reliable and provides long-term protection for electric motors in various industrial and domestic applications.