Understanding Cable Size Types | mm, mm2, B&S, AWG

Navigating Wire Gauges: mm and mm² Explained

mm: Precision in Smaller Cables - The Role of Diameter

In electrical terms, millimeters (mm) refer to the diameter of a wire, a straightforward measure that's particularly relevant for smaller cables. This measurement is about precision, ensuring that the wire fits perfectly where it's intended, especially in compact spaces. However the cable size will typically be a little larger than this allowing for the cable insulation and sheath.

The Importance of mm² in Cable Performance - Understanding Cross-Sectional Area (CSA)

The cross-sectional area, measured in square millimeters (mm²), is a crucial factor in determining a cable's current carrying capacity. It's not just about the size but about the cable's ability to conduct electricity safely and effectively.

Distinguishing Diameter from Area - Why Both Measurements Matter

While diameter (mm) gives a quick visual indication of the wire's size, CSA (mm²) delves deeper, revealing the wire's electrical capabilities. It's essential to consider both to ensure that a cable is suitable for its intended electrical application.

Technical Insights for Practical Use

Selecting the correct wire requires more than just eyeballing the diameter. Knowing both the mm and mm² of a wire helps in making informed decisions, balancing physical fitting and electrical suitability.

Navigating Wire Gauges: B&S and AWG Explained

British Standard Wire Gauge (B&S): A Traditional Measure in Australia

  • Historical Context: Originating from the British Standard, B&S has been a longstanding measure for wire diameters, particularly in Commonwealth countries.
  • Current Relevance in Australia: Despite the global shift towards the metric system, B&S remains a prevalent standard in certain Australian industries, reflecting its historical significance and practical utility.

American Wire Gauge (AWG): A Global Standard

  • Introduction to AWG: American Wire Gauge, commonly known as AWG, is a standardized system used primarily in North America. It plays a significant role in measuring the sizes of electrically conducting wires.
  • Characteristics of AWG: The AWG system is based on a logarithmic scale where a higher gauge number indicates a thinner wire. This system is integral in applications ranging from household electrical wiring to electronic equipment.

B&S and AWG in Australia: A Unique Coexistence

  • Synergy in Sizes: In a unique industry practice, Australian cable manufacturers often align B&S sizes with those of AWG. This alignment facilitates cross-referencing and compatibility in various applications.
  • Understanding the Equivalence: While B&S and AWG are fundamentally different systems, their correlated sizes in the Australian context simplify the selection and use of wires across diverse projects.

Technical Considerations for B&S and AWG

  • Navigating Between Systems: Professionals working with electrical systems in Australia need to be adept at navigating both B&S and AWG measurements, especially when dealing with international specifications or legacy systems.
  • Importance of Accurate Gauge Selection: Choosing the correct wire gauge is critical not just for ensuring physical compatibility but also for maintaining electrical integrity and safety.

Practical Examples of Cable Sizing

Example 1: Selecting a Cable for a Small LED Light in a Motorhome

Scenario: A customer is outfitting a motorhome with a small LED light. The light requires a minimal current and is situated close to the power source.

Requirement: A cable that can efficiently power the LED light without being excessively bulky, ensuring easy installation in the confined space of a motorhome.

Selection Process:

  1. Cable Size: A 3mm auto cable is chosen. This size is sufficient for the low current requirement of the LED light.
  2. Reasoning: The 3mm cable has a current capacity of 16A, well above the 1-3A needed for the LED light, and provides a balance between physical flexibility and electrical capability. It's easy to route in tight spaces typical of motorhome interiors.
  3. Outcome: The 3mm auto cable efficiently powers the LED light, ensuring minimal energy loss and optimal illumination, while its small size makes it unobtrusive and easy to install.

Example 2: Choosing the Right Cable for a 50A DC-DC Charger in a 4x4 and Caravan Setup

Scenario: Imagine the electrical current as water flowing through a pipe, and you're trying to connect a robust water supply (the 50A DC-DC charger) between your 4x4 and caravan over an 11-meter distance.

Initial Cable Choice: You start with an 8B&S cable, akin to a medium-sized water pipe. It seems adequate for the flow (current) you need to pass through.

The Voltage Drop Challenge: However, just like water pressure drops over a long distance in a pipe, electrical voltage drops over a long cable. The longer your pipe, the more pressure (voltage) you lose by the time it reaches the end.

Upsizing to 4B&S – The Wider Pipe Solution: To combat this drop in pressure (voltage drop), you switch to a 4B&S cable, which is like using a wider pipe. The wider the pipe, the more water (current) it can carry without losing pressure (voltage). It's a bit more bulky and might require more effort to lay down, but it ensures that the water pressure (voltage) remains strong all the way through to your caravan.

Outcome: By using the 4B&S cable, you effectively maintain the 'water pressure' (voltage) from your 4x4 to your caravan, ensuring that your electrical system operates efficiently, even over the lengthy 11-meter 'pipe' run.