Power disconnector LN1 4-pole 125A LN1-4-125-I 112000

Application and functionality in industrial installations

This device is a key element in distribution systems where reliable isolation of high-current circuits is required. As a main disconnector with a rated continuous current of 125 A, it is suitable for circuits powering electric motors (up to 55 kW at 400 V) and other industrial loads. Its construction allows for safe disconnection of voltage to perform maintenance or repair work, complying with safety requirements for power supply devices.

It is worth noting its versatility – it can serve not only as a main disconnector but also as:

• Safety disconnector (in specific configurations),
• Emergency switch (thanks to appropriate marking and mechanism),
• Maintenance disconnector.

Thanks to this, a single device covers many operational scenarios, simplifying component selection for distribution boards. It is designed for operation in power supply networks with a voltage up to 690 V, making it suitable for both standard 400 V installations and systems with higher rated voltages.

Construction, mounting, and resistance to external conditions

The device is built on a solid plastic housing providing an IP20 protection rating from the front – protecting against access to live parts by fingers or tools with a diameter above 12 mm. External dimensions (120 mm width, 145 mm height, and 88 mm depth) allow for efficient use of space in distribution boards while maintaining required insulation clearances.

A key structural element is the locking mechanism, which ensures the control lever remains in the selected position (I - ON, + - neutral/disconnected, 0 - OFF). The "rocking" lever (grey) enables intuitive manual operation. For installers, the possibility of intermediate mounting and permanent fixing of the device in the distribution board is important.

Regarding electrical connections, cage terminals (box terminals) are used, which accept:

• Rigid and flexible copper conductors with a cross-section from 6 to 95 mm² (depending on the connection configuration),
• Busbars with a thickness up to 16 mm x 5 mm,
• Aluminum conductors up to 16 mm².

This flexibility facilitates integration with various types of cabling without the need for additional end fittings or adapters. It is worth adding that the device can be expanded with an optional motor drive or undervoltage release, opening the way for automation of switching processes in remote systems.

Safety and short-circuit resistance

Under fault conditions, the device exhibits high resistance to short-circuit currents. The rated conditional short-circuit current (Iq) is as high as 100 kA at 400 V, meaning that with appropriate overcurrent protection (e.g., gG fuses), the disconnector will withstand a short-term short-circuit current flow without mechanical or electrical damage. The rated short-time withstand current (Icw) is 2 kA for the duration of the short circuit (e.g., 1 second), providing time for upstream protection devices to operate before permanent damage to the main contacts occurs.

Additional features increasing safety include:

• Total short-circuit breaking time below 10 ms – fast reaction minimizes thermal and dynamic effects of the short circuit.
• Impulse withstand voltage of both main and auxiliary contacts at 6000 V – ensures insulation even during voltage surges.
• Overvoltage category III – adapted for industrial installations powered directly from the distribution network.

The device complies with IEC/EN standards for isolating switches and main disconnector characteristics, confirming its suitability for professional electrical installations in accordance with current HSE regulations. Thanks to a high number of mechanical switching cycles (up to 20,000 operations) and electrical cycles (up to 7,500-10,000 operations depending on load), it ensures a long service life even with frequent use as a service or emergency switch.