Power disconnector LN4, 3-pole 1250A LN4-1250-I 112014

Application and Key Features in Industrial Installations

A power disconnector with a rated continuous current of 1250 A is a device intended for handling high-current circuits where reliable isolation and safe disconnection are required. With three poles and the capability to operate at voltages up to 690 V, it is suitable both as a main disconnector in industrial switchboards and in power supply systems for motors or heating equipment. Its construction allows it to fully perform the functions of a main disconnector, as well as serve as an emergency switch-off device – which is crucial in situations requiring rapid power disconnection for personnel safety or equipment protection.

The device features high short-circuit current resistance: it withstands a short-time withstand current of 25 kA, and when coordinated with appropriate protective devices (e.g., fuses), achieves a conditional short-circuit current of up to 100 kA. This performance makes it a robust component in circuits exposed to high current surges or short-circuit risks. Notably, at 400 V, the device can safely operate with power up to 710 kW (AC-23 category), making it suitable for controlling high-power motors.

Construction, Installation, and Expansion Options

The device is designed for fixed mounting within a switchboard cabinet, ensuring stability and safety during long-term operation. Main terminal connections are made via pin/busbar connections, facilitating integration with busbar systems and reducing installation time. The disconnector is equipped with a mechanical lever drive with locking functionality – meaning that after switching, the contact position is permanently maintained, giving the operator certainty about the circuit status (open/closed).

The device dimensions are 210 mm in width, 207 mm in height, and 401 mm in depth – these should be considered when planning cabinet installation. The front protection rating is IP20, providing protection against solid objects larger than 12 mm, but additional covers or installation within an enclosure with a higher protection rating (IP40 or above) is required for full protection against dust and water.

Thanks to the modular concept of the LN4 series, the device can be easily expanded with additional functions:

• Motor drive – an optional remote drive enables automatic disconnection or connection of the circuit without manual intervention.
• Undervoltage release – allows automatic power disconnection in case of voltage drop below a set threshold.
• Mechanical interlocks – solutions are available to lock the manual drive of multiple devices simultaneously, enhancing safety during maintenance work.

Compliance with Standards and Operating Conditions

The device is designed to maintain full electrical parameters even at ambient temperatures up to +50°C – which is important in hot technical rooms or production halls. It does not include built-in auxiliary contacts (either normally open or normally closed), but thanks to compatibility with a wide range of accessories from the LZM/LN/NZM/N series, they can be easily added according to project requirements.

Key device parameters include a rated continuous current of 1250 A and a maximum operating voltage of up to 690 V AC. Regarding short-circuit resistance, the device withstands a short-time current of 25 kA and a conditional short-circuit current of up to 100 kA with appropriate protective coordination. Connections are made via pin/busbar method for three poles, and the drive mechanism is based on a lever with mechanical locking. The overall construction supports optional accessories such as motor drives or undervoltage releases, allowing flexible adaptation to industrial automation project requirements.