what is means re, rm, se, sm for cable conductors?

re     :  solid single round conductor
rm    :  multi wire round  conductor
se    :  solid sectorial conductor
sm   :  multi wire sectorial conductor

    RE: Single-wire round conductor
    SE: Single-wire sector-shaped conductor
    RM: Multiwire stranded round conductor
    RMV: Multiwire stranded round compacted conductor
    SM: Multiwire sector-shaped conductor

sm/se - conductor needs to be pre-rounded
rm = round multi-stranded
rm (v) = round multi-stranded compacted
sm = sector stranded
re = round solid
se = sector solid

In the past, the terms in the NEC® related to conductor stranding were all over the book but not properly defined in Article 100.

NEC Tables 312.6(A) and (B) specify the minimum wire-bending space required at terminals and the minimum width of wiring gutters. These tables have only two columns describing the conductor type; "Compact Stranded Aluminum", and "All Other Conductors".

How would one know which column to use for an installation into a cabinet using stranded aluminum wire without an Article 100 definition for the three different types of stranding configurations? If it's not "compact stranded" aluminum wire, then Tables 312.6(A) and (B) would consider it "all other conductors" and require a greater wire-bending space for the installation.

Most code readers had no idea that the definition of "compact stranding" has been at the bottom of Tables C.1(A) through C.13(A) in Annex C for many years.

The term "compressed" was mentioned (but not defined) in footnote 3 under Chapter 9, Table 8; and the term "concentric" was mentioned (but not defined) in Chapter 9, Table 1, foot note (10), and Annex C.

Now there are definitions that will help the code reader know exactly which type of stranding applies.

Compact Stranding is a stranding method where each layer of strands is pressed together, minimizing gaps between the strands so the overall diameter of the finished conductor is less than a concentric stranded conductor and also less than a compressed stranded conductor.

Compressed Stranding is a stranding method where the outer layer of conductor strands is pressed together which results in the overall diameter of the finished conductor being smaller than a concentric stranded conductor but larger than a compact stranded conductor.

Concentric Stranded conductors have a straight central strand surrounded by one or more layers of strands, helically laid in a geometric pattern.

Source : You are not allowed to view links. Register or Login

Code    Description

R    Circular conductor

S    Sector shaped conductor

E    Solid conductor

M    Stranded conductor

RE    Circular conductor, solid

RM    Circular conductor, stranded

SE    Sector shaped conductor, solid

SM    Sector shaped conductor, stranded

OM    Oval shaped conductor, stranded

RF Flexible stranded round conductor

H    Waveguide

/V    Compacted conductor

RM/V Circular, stranded, Compacted conductor

Conductor cross-section, shape and structure
Code    Description
R    Circular conductor
S    Sector shaped conductor
E    Solid conductor
M    Stranded conductor
RE    Circular conductor, solid
RM    Circular conductor, stranded
SE    Sector shaped conductor, solid
SM    Sector shaped conductor, stranded
OM    Oval shaped conductor, stranded
H    Waveguide
/V    Compacted conductor

Conductor cross-section, shape and structure
Code    Description
R    Circular conductor
S    Sector shaped conductor
E    Solid conductor
M    Stranded conductor
RE    Circular conductor, solid
RM    Circular conductor, stranded
SE    Sector shaped conductor, solid
SM    Sector shaped conductor, stranded
OM    Oval shaped conductor, stranded
H    Waveguide
/V    Compacted conductor

IEC 60228: Conductors of Insulated Cables
IEC 60228 is the principal standard that classifies conductors for electrical installations. It specifies requirements for conductor types, sizes, and resistance values.

Class 1 (Solid Conductors): Includes RE (Round, Solid) and SE (Sector-Shaped, Solid).

Class 2 (Stranded Conductors): Includes RM (Round, Stranded) and SM (Sector-Shaped, Stranded).

Key Characteristics
RE (Round, Solid)

IEC 60228: Solid Class 1

EN 13602: Standards for copper conductors

Applications: Fixed installations, building wiring

Advantages: High mechanical strength, lower electrical resistance

RM (Round, Stranded)

IEC 60228: Stranded Class 2

EN 13602: Standards for copper conductors

Applications: Flexible connections, automotive wiring, portable devices

Advantages: Flexibility, ease of installation, vibration resistance

SE (Sector-Shaped, Solid)

IEC 60228: Solid Class 1

Applications: High-density power distribution, urban networks, aerospace

Advantages: Space efficiency, high current carrying capacity

SM (Sector-Shaped, Stranded)

IEC 60228: Stranded Class 2

Applications: Industrial automation, robotics, power cables in confined spaces

Advantages: Combination of flexibility and space efficiency

Technical Details
RE (Round, Solid)
Construction: Single solid wire with a uniform round cross-section.

Diameter Range: From very fine wires (0.5 mm²) to larger sizes used in power distribution.

Resistance: Lower due to the absence of air gaps, ensuring efficient electrical conductivity.

Installation: Best for static installations where the cable does not need to flex or move.

RM (Round, Stranded)
Construction: Composed of multiple smaller wires twisted together to form a round conductor.

Stranding Types: Standard (basic twist) or compact (tightly packed strands for better performance).

Diameter Range: Similar to RE but available in more flexible configurations.

Flexibility: High, making it suitable for dynamic applications like movable machinery and vehicles.

Installation: Easier to install in constrained spaces due to its flexibility.

SE (Sector-Shaped, Solid)
Construction: Single solid conductor with a sector (wedge) shape.

Space Utilization: Designed to fit together with other sector-shaped conductors in a cable to reduce overall diameter.

Mechanical Strength: High due to the solid structure, but less flexible.

Applications: Used in cables where high current carrying capacity and compact design are critical.

SM (Sector-Shaped, Stranded)
Construction: Multiple smaller wires twisted to form a sector-shaped conductor.

Flexibility: Provides the best of both worlds: the flexibility of stranded conductors and the space efficiency of sector-shaped conductors.

Stranding Techniques: Can be concentric (standard) or compact (for even tighter packing).

Applications: Suitable for high-power applications in industrial settings and complex machinery.

Detailed Use Cases
RE (Round, Solid)
Building Wiring: Used for wiring in residential and commercial buildings where flexibility is not required.

Switchgear and Control Panels: Provides reliable connections that need to remain static.

RM (Round, Stranded)
Automotive Wiring: Ideal for car wiring harnesses due to its ability to withstand vibrations and flexing.

Portable Appliances: Used in the cables for appliances that are frequently moved or handled.

SE (Sector-Shaped, Solid)
Urban Power Distribution: Efficiently packed within multi-core cables, used in underground and high-rise power distribution systems.

Aerospace Applications: Where space and weight are critical, and high current carrying capacity is needed.

SM (Sector-Shaped, Stranded)
Industrial Automation: In machinery and automation systems where cables must navigate through tight spaces and handle movement.

Robotic Systems: Provides flexibility and compact design essential for robotic arms and moving parts.

Advantages and Challenges
RE (Round, Solid)

Advantages: High mechanical strength, low resistance

Challenges: Limited flexibility, more difficult to install in tight spaces

RM (Round, Stranded)

Advantages: Flexibility, ease of installation, good vibration resistance

Challenges: Slightly higher resistance, more complex manufacturing process

SE (Sector-Shaped, Solid)

Advantages: Space-efficient, high current carrying capacity

Challenges: Limited flexibility, challenging to handle during installation

SM (Sector-Shaped, Stranded)

Advantages: Flexibility and space efficiency combined, high performance in dynamic environments

Challenges: Higher manufacturing complexity and cost