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In-Depth Disassembly of MNS Low-Voltage Switchgear: A Comprehensive Analysis from the Frame to the Drawout Units

Release time:

2026-05-20

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Abstract

The MNS low-voltage withdrawable switchgear is a low-voltage distribution device manufactured under license from ABB, widely used in power plants, substations, industrial and mining enterprises, municipal infrastructure, and other sectors. As one of the most highly modular low-voltage switchgear types, the MNS features… Compact structure, high drawer interchangeability, safe and reliable Well-known. This article will take you through an in-depth analysis of the MNS switchgear, covering everything from its frame and busbar system to compartment layout and drawer units.

I. Cabinet Frame: Modular C‑section Steel Framework

The MNS cabinet body adopts C‑section modular structure , this is the foundation of all components.

Core design parameters:

Design Elements	Specifications and Parameters
Modular Datum	E=25mm (DIN 43660 standard)
Profile thickness	2mm high-strength aluminized zinc-coated steel sheet
Connection method	Self-tapping locking screw / 8.8-grade hex bolt
Preservative treatment	Galvanized finish or aluminum-zinc coated sheet in its original color
Lifting structure	Top frame with lifting lugs

Structural features:
The C‑type frame is punched at 25 mm intervals and precisely assembled with bolts to form a robust structure. This modular design enables… Simply by adjusting the position of the compartment partition, functional units can be arranged flexibly. , highly versatile.

Cabinet dimension series:

Width: 600/800/1000 mm

Depth: 600/800/1000 mm

Height: 2200 mm

II. Busbar System: The Aorta of Electrical Power Distribution

The busbar system of MNS is divided into Main busbar and Distribution busbar (vertical busbar) Two levels.

1. Main busbar

The main busbar is arranged within the switchgear. In the rear independent busbar compartment , Copper busbars are manufactured in accordance with German industrial standards.

Configuration features:

A single-layer or double-layer arrangement may be adopted.

The double-layer busbar system is arranged on the upper and lower levels, respectively.

Copper busbar specifications: 30×10 mm, 40×10 mm, 60×10 mm

The rated current can reach 6300A

Rated short-time withstand current: 30–100 kA (1 second)

Connection process: Secure using bolts coated with ESLOK, conical spring washers, and a torque wrench; this design has been approved. Maintenance-free certification 。

2. Distribution busbar (vertical busbar)

The distribution busbar is installed within the multifunctional partition and is responsible for distributing electrical power from the main busbar to each drawer unit.

Technical Specifications:

L-shaped right-angle copper busbar, with a cross-section of 50×30×5 mm.

Rated current: 1000–2000 A

Short-time withstand current: 50–80 kA

Unique Design — Multi-Functional Divider:
The distribution busbar is installed within an insulating, multi‑functional partition, a design that serves multiple purposes:

It meets the IP20 protection rating against electric shock. Prevents fingers from being accidentally inserted.

possessing Fault‑tolerant arc performance

Isolation compartment and busbar compartment

The material has Flame-retardant, self-extinguishing, arc-quenching Characteristics

III. Compartment Layout: A Safety Design with Four Separate Zones

The MNS cabinet is divided into Four independent compartments , Rooms are separated from one another by steel panels or high‑strength flame‑retardant plastic functional panels.

Compartment Name	Location	Equipment enclosure	Function Description
Main Busbar Room	Rear or top of the cabinet	Main busbar, copper busbar	Electric Power Collection and Distribution
Drawer compartment (functional unit room)	Front of the cabinet	Drawer unit, components	Control and Protection of Each Circuit
Cable Room	Rear of the cabinet or right side of the front of the cabinet	Outgoing cables, terminal blocks	Incoming and outgoing line connections
Busbar compartment	Upper part of the cabinet front	Control of the auxiliary busbar and secondary components	Secondary control circuit

Isolation characteristics:

A metal panel with ventilation holes separates the upper and lower drawers.

Effectively prevents failures caused by switching device malfunctions. Arc propagation

Prevent the escalation of accidents caused by short circuits between busbars and other lines.

IV. Drawer Units: The Core of Modularity

MNS’s drawer system is a hallmark of the cabinet design, engineered on a 25 mm modular grid and supports Mixed configuration of multiple specifications 。

1. Drawer Specification Series

Drawer specifications	Height	Rated current range	Applicable Scenarios
8E/4 (1/4 unit)	50mm	≤63A	Small-capacity feeder circuit
8E/2 (1/2 unit)	100mm	≤125A	Medium and small capacity circuit
8E	200mm	≤250A	Standard power feed circuit
16E	400mm	≤400A	High-capacity circuit
24E	600mm	≤630A	Extra-large-capacity circuit

Installed capacity: Effective installation height per cabinet 1800mm (72E), can hold up to 36 drawer units 。

2. Three-position operating mechanism for the drawer

Each drawer unit is equipped with Operating mechanism with mechanical interlocking , enabling three distinct positions:

Location	Status	Mechanical interlocking function
Connection Location	Both the main circuit and the secondary circuit are energized.	The drawer cannot be pulled out to prevent plugging and unplugging under load.
Test position	Main circuit disconnected, secondary circuit connected.	Control loop testing can be performed.
Separation position	Both the main circuit and the secondary circuit are open.	The drawer can be safely pulled out for replacement.

Additional security features: Can be on the control handle Padlock , to prevent unauthorized operations.

3. One-time connector

A single plug-in connector is a critical component for connecting the drawer to the vertical busbar:

Craftsmanship features:

The contacts undergo during the manufacturing process Functional and Stress Testing

Test data and the serial number are engraved on the contact assembly. Fully traceable throughout the entire process

Tin-plated, rated current 250 A

Equipped with Plug protective cover , ensure complete isolation before contact

New plug technology:

The spring uses Manganese steel material + Heat treatment, with stable and reliable performance

Laminated structure (4 copper plates per group), with independent contact springs for each group.

Minimal pressure variation after 500 mating cycles, with excellent durability.

4. Adapter

The adapter enables the vertical busbar to achieve horizontal power distribution. Optimize cabinet space utilization ：

Adapter Type	Rated current	Features and Benefits
Four-circuit adapter	45A per circuit	Four functional units are arranged at the same horizontal level.
Dual-circuit adapter	63A per circuit	Two functional units are at the same horizontal level.

Standard configuration for each functional unit 20 auxiliary terminals , meeting the requirements for control signal transmission.

V. Summary of Technical Parameters

Parameter item	MNS Standard Performance
Rated operating voltage	400V/690V
Rated Insulation Voltage	690V~1000V
Rated impulse withstand voltage	8kV
Rated current of the horizontal busbar	≤6300A
Rated current of the vertical busbar	≤2000A
Rated short-time withstand current	30~100 kA (1 second)
Rated peak withstand current	≤220kA
Protection rating	IP30~IP54
External dimensions (width × depth × height)	600/800/1000×600/800/1000×2200mm

VI. Summary of MNS Core Advantages

Modular design : With 25 mm as the basic module, it features a flexible structure and offers over 200 combination options.

100% drawer interchangeability : Drawers of the same specification can be interchanged at will, making maintenance and replacement convenient.

Quarantine in Zone Four : The busbar compartment, drawer compartment, cable compartment, and auxiliary busbar compartment are physically isolated, preventing fault propagation.

Three-station mechanical interlocking : Clear identification of connection, testing, and disconnection positions to prevent misoperation.

Maintenance-free busbar connection : Special fastening process, no periodic tightening required

Fault‑tolerant arc : The multifunctional partition plate features arc-extinguishing and arc-suppression capabilities.

About Hunan Electrical Appliance Co., Ltd.

Hunan Electrical Appliance Co., Ltd. As a professional manufacturer of complete electrical equipment covering the entire value chain, we possess independent R&D, production, and service capabilities for MNS low-voltage withdrawable switchgear. We maintain end-to-end in-house control across the entire process—from design and sheet metal fabrication to system integration and commissioning—providing customers with safe, reliable, and highly efficient low-voltage power distribution solutions.

Whether it’s an industrial plant, a commercial complex, or a municipal project, Hunan Electrical Appliance Co., Ltd. can provide standardized or customized MNS complete solutions tailored to your specific needs. Feel free to call us for inquiries, submit your drawings for a quote, or visit our factory for a site inspection!

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Hunan Chengyuan Electrical CO.,LTD