Hollow Conductor

Hollow conductor, made of oxygen free copper, aluminum or stainless steel, offers a continuous conduit free of seams and welds thus reducing the risks of leaks, and the super pure metal material provides superior electrical conductivity and also offers high thermal conductivity, and it offers significant advantages in terms of current density, cooling, weight, and compactness, making them suitable for high-power, space-constrained, and weight-sensitive applications.

 

Description

 

Fabmann supplies high quality copper hollow conductors with a wide variety of cross-section from complex to standard profile shapes, and our copper tubes and hollow conductor tubing are suitable for most diverse engineering applications. We can produce square and rectangular tubing from width with few millimeter to over 100 millimeter with extremely tight dimension tolerance, and they are available in a variety of tempers like hard, half hard, soft annealed. We can supply a wide range different customized shape such as square & rectangular with round bore, or just standard square and rectangular copper tubing, oval and D-shape for both copper and aluminum hollow conductors. For stainless steel hollow conductors usually rectangular tubing, we can supply thin wall thickness only 0,5mm.

 

What is the application of hollow conductors?

 

Hollow conductors offer significant advantages in applications requiring high currents, efficient cooling, and reduced weight. Their versatility makes them suitable for a wide range of applications across various industries as indicated below:

 

Application of Hollow Conductor

 

√ Electric vehicles (EVs), electric vehicle charging systems and battery packs due to their high current-carrying capacity and weight reduction

   potential.

√ MRI devices / gradient coils

√ High power electromagnets such as particle accelerators, fusion reactors, magnetic levitation (Maglev) system,

√ Generators, stator direct cooling

√ Induction furnaces, induction heating and melting

√ Plasma research devices

√ Electrodynamic vibration test systems

√ Ion implantation units for the microcircuit industry

√ High gradient separators

√ Waveguides

√ Renewable energy, transformers in solar power inverters and wind turbine generators.

√ Liquid cooled transformers

√ Busbars, high-current power distribution, hollow conductors are used as busbars in electrical systems for distributing high currents efficiently,

   reducing power losses and improving safety.

√ Aerospace, the lightweight and high-performance characteristics make them attractive for use in aircraft and spacecraft electrical systems.

√ Military, high-power radar systems, lasers, and other military equipment.

 

Why does hollow conductor generate heat?

 

Heat generation in hollow conductors is a complex phenomenon influenced by various factors, including AC resistance, eddy currents, dielectric losses, cooling limitations, and high current densities. By understanding these factors and implementing appropriate design and operational measures, Fabmann can help you to minimize heat generation and ensure the safe and efficient operation of hollow conductors, and you shall be mindful of the causes of heat generation below:

 

√ AC resistance

1. 1. Skin effect, when alternating current (AC) flows through a conductor, the current tends to concentrate near the surface due to the skin effect. This results in higher current density near the surface, leading to increased heat generation.
2. 2. Proximity effect, in bundled conductors, such as hollow conductors with multiple hollow tubes, the current distribution can be further affected by the proximity effect, which causes uneven current distribution and localized heating.

√ Eddy Currents

1. 1. Magnetic fields, when a conductor is subjected to a changing magnetic field, eddy currents are induced within the conductor, and they circulate within the conductor and dissipate energy as heat.
2. 2. Hollow space, the hollow space in a hollow conductor can act as a path for eddy currents, especially for hollow aluminum conductor.

√ Dielectric Losses

1. 1. Insulation materials, they can contribute to heat generation due to dielectric losses, and it can occur when the electric field associated with the AC current causes polarization of the insulation material.
2. 2. Temperature dependence, dielectric losses typically increase with temperature, creating a positive feedback loop that can lead to further heating.

√ Insulation design, fillers and insulation can impede heat transfer, further reducing the cooling efficiency.

√ High current densities, it can lead to significant heat generation.

√ Frequency, higher frequencies can lead to increased skin effect and eddy current losses, resulting in more heat generation.

√ Material properties: The electrical conductivity and magnetic permeability of the conductor material can influence heat generation.

√ Environmental condition, ambient temperature and airflow can affect the heat dissipation performance.

 

Hollow conductors are often designed to carry high current densities to take advantage of their weight and size benefits, yet, high current densities can lead to significant heat generation. Therefore, you shall be reminded that overloading or operating hollow conductors beyond their rated current capacity can exacerbate heat generation issues.

 

Dimension Check of Hollow Conductor

 

Production Control

 

Hollow conductors are used in a variety of applications, and production process involves a number of steps, including casting, extrusion, cold rolling, drawing, and annealing. Production control is essential to ensure that the final product meets the required specifications. To deliver sound quality, Fabmann takes strict production control from raw material to packing, and each stage of production process is under our quality radar system. Below is a summary of what our quality team cares about most.

 

 

Hollow Conductor Material Option (Aluminum, Stainless Steel & Oxygen Free Copper)

 

Aluminum, stainless steel, and copper are three commonly used metals in hollow conductors, each with distinct conductivity & anti-corrosion characteristics. Here's a comprehensive comparison of their conductivity, cost, weight, and other relevant properties:

 

• √ Conductivity

Oxygen free copper, it has the highest conductivity among the three, with a conductivity above 58.3 MS/m, and it means that it can carry the most current for a given cross-sectional area.

Aluminum (1070), it has a conductivity of 35MS/m, significantly lower than copper but still higher than stainless steel.

Stainless steel (304L & 316L), it has the lowest conductivity among the three with a conductivity of 1.40 MS/m.

• √ Cost

Aluminum (1070), it is the most cost-effective option.

Stainless steel (304L& 316L), it is more expensive than aluminum.

Oxygen free copper, it is the most expensive option

• √ Weight

Aluminum, it is the lightest option, with a density of 2.7 g/cm³.

Stainless Steel, it is heavier than aluminum but lighter than copper, with a density of 7.9 g/cm³.

Oxygen free copper, copper is the heaviest option, with a density of 8.9 g/cm³.

• √ Other Properties:

Corrosion resistance, aluminum forms a protective oxide layer that makes it more resistant to corrosion than stainless steel and copper, however, copper is more resistant to oxidation at high temperatures. Stainless steel also offers excellent corrosion resistance.

Tensile strength, stainless steel has the highest tensile strength among the three, making it suitable for high-stress applications. Copper has moderate tensile strength, while aluminum has the lowest.

Ductility, aluminum is the most ductile, followed by copper and then stainless steel. This makes aluminum easier to bend and other secondary fabrication.

• √ Application Considerations

High-Current application, copper is preferred due to its high conductivity and smaller conductor size.

Cost-Sensitive applications, aluminum is often chosen for its affordability, especially in large-scale projects.

Corrosion-Resistant applications, aluminum and stainless steel are suitable for applications exposed to harsh environments.

High-Strength applications, stainless steel is the best choice for applications requiring high mechanical strength, and they are often used for water cooled windings of turbogenerator.

The choice among aluminum, stainless steel, and copper depends on the specific application and its requirements. Copper offers the highest conductivity, aluminum provides cost-effectiveness and lightweight properties, while stainless steel excels in corrosion resistance and high strength. By considering these factors, Fabmann can assist you to select the most suitable metal for your hollow conductor projects.

 

Insulation of Hollow Copper Conductor

 

What are the insulation types for hollow conductors?

 

Hollow conductor with Insulation is essential for the safe and reliable operation of magnets, and it helps to prevent electrical breakdown, improve heat dissipation, protect against environmental factors, enhance mechanical strength, and reduce corona discharge. Without proper insulation, hollow conductors would be susceptible to a variety of problems that could lead to power outages, equipment damage, and safety hazards. Fabmann can help you to choose the most economic way of insulation, and the following insulations are the popular ones for hollow conductor insulation:

 

• √ Sintered Polyester Imide Film
• √ Polyester Imide Film with Enamel
• √ Polyester Imide Film with Enamel + Glass Fiber
• √ Polyester Imide Film with Enamel + Industrial Non-woven Fabric

 

All of these insulation materials can give very good insulation performance, in particular, polyester Imide with glass fiber can achieve highest thermal class 240.