Hollow conductor shapes

Hollow Conductors

Custom-built electrical conductors for many different applications

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When high magnetic fields are required, the magnetic winding is made from internally cooled hollow sections. While the majority are still looking for square hollow conductor with a round or rectangular cooling channel, the demand for different outer dimensions and hole sizes is growing.

Luvata has been manufacturing copper hollow conductors for the most demanding applications for nearly sixty years. Hollow conductors are sometimes also referred to as: 

  • water cooled conductors 
  • hollow wire 
  • hollow tube
  • hollow magnet wire 
  • square copper tube 
  • profile tube 
  • rectangular copper tubing
  • tubular bus conductors 
  • induction coil tubing 
  • induction heating tube
Widest range of tools on the market

Our long history in making hollow conductors has given us thousands of tools for creating most sizes of conductors with very short lead times without tooling costs. The sizes start from 3 x 2 mm (< 0.07 kg/m) and continue up to above 100 mm in width (>30 kg/m).  We can also supply conductors in small quantities for testing and for prototype purposes.  

Hollow conductor shapes 

Technical data expander header icon

All impurities reduce the electrical conductivity of copper, which is why we make Luvata hollow conductors from OF-OK® high purity oxygen-free copper. As a result of its purity, Luvata OF-OK has typical electrical conductivity of 100-102 %IACS and thermal conductivity of 390 W/Km.

The maximum oxygen content of 5 ppm (0.0005%) makes the material immune to hydrogen embrittlement and ensures safe joining with all brazing and welding methods.

The OF-OK used in our hollow conductors is cast in our own  foundry in electric furnaces using selected high purity raw materials. This means we can control the whole manufacturing process from casting to signing the inspection certification, and ensure the consistency of our product from batch to batch.

When necessary OF-OK is alloyed with silver (Ag) to increase both the softening temperature and creep resistance of the alloy without any significant sacrifice of its other properties.


AlloyENASTMElectrical conductivityThermal conductivity
   MS/mIACS% W/Km 
 CuAg0.04(OF)CW017A C10400 57,7  99,5 388


Applications expander header icon
  • Electric vehicles (EVs) / stator direct cooling
  • MRI devices / gradient coils
  • Magnets for high energy physics applications
  • Particle accelerators
  • Generators
  • Induction furnaces / induction heating and melting
  • Plasma research devices
  • Electrodynamic vibration test systems
  • Ion implantation units for the microcircuit industry
  • High gradient separators
  • Waveguides 
  • Liquid cooled transformers 
Electric vehicles (stator direct cooling)

Our hollow conductors provide new possibilities to cool down electric motors. The internal cooling hole on the stator windings enables efficient thermal transfer out from the core - exactly from the source where the heat is generated. Cooling with air improves the performance significantly and liquid cooling even more. As a result increased power and torque are achieved by direct cooling with Luvata's hollow conductors.

Direct versus indirect cooling

In electric motors, the current flows in the windings, which are made of copper because of its low resistance. Electrical losses are an unavoidable obstacle and increase with the amount of current; for example, doubling the current quadruples the losses, which increases heat in the motor. In addition, magnetic losses heat both the stator and the rotor, further increasing the heat load. This heat can be extracted by direct or indirect cooling. The big benefit of direct cooling is that it treats the heat where it is generated, in the winding itself instead of in the housing. Effective cooling of the stator also ensures a lower rotor temperature, enabling the use of less expensive lower temperature graded permanent magnets.

The benefits of direct-cooled electrical motors

Direct cooling offers the highest power density for an electric motor – especially continuous power output – alongside excellent efficiency over a broad range. Partial load is the most realistic use case for an electric motor, and tests conducted have shown that a direct-cooled motor offers approximately twice the power output at peak load and three times the power output at continuous steady-state operation compared to a standard, indirect-cooled motor.

The higher efficiency of direct-cooled motors means that smaller power units can be used in EVs, saving both weight and costs. It also enables the use of electric powertrains in larger vehicles such as trucks. Direct-cooled motors can use standard, cost-effective materials, including magnets, providing higher performance at a lower cost – a key enabler for the wider adoption of EVs.

Read more about direct cooling in our white paper here

Mileon - the longest hollow conductor in the world expander header icon

Every joint in a water cooled magnet is a potential cause of leakage. So the longer each individual coil is, the more the risk is reduced. With the aim of eliminating the joints within the magnet altogether, we have developed extremely long Mileon® coils.  The length of these coils, rather than being measured in meters, is now measured in hundreds, or even thousands of meters. The coil weight can be as high as 2500 kg - a single coil, jointless.

Mileon coils are manufactured using only oxygen-free copper, and are subject to the same stringent quality criteria that we apply to our other hollow conductor products. 
Using large Mileon coils means that less scrap is generated in the magnet manufacturing process, and expensive copper is saved. The longer coils also provide increased flexibility in production compared with shorter coils that are cut to predetermined lengths.

Mileon coils are typically delivered on large wooden spools, which require less packaging materials and are recyclable. Alternative environmentally friendly packaging options are also available to meet every customer's unique needs.

Mileon coil advantages
  • No joints
  • Highest quality copper
  • Less copper wastage
  • Precise delivery quantities


Delivery forms expander header icon
Mileon® jointless long lengthsUp to 2500 kg depending on dimension, delivered on wooden reel
Loose coils, pancake coils or LWC coilsMax 50-400 kg depending on dimension
Spools for small sizesPlywood or plastic spools
Straight lengthsup to 16 meters
Mileon® wooden reel 


  HC_ESA0443        download  

spool number
D (mm)80090090010009001000120012001600
D1 (mm)4004004005007007006009001200
L (mm)480480630730640730730730940
l (mm)400400550600550600600600740
d (mm)132132132132132132132132132


Loose coil

Loose coil 


Pancake coil

Pancake coil 


LWC coil
  LWC coil


Spool for small sizes 

   Spool for small size

FAQ expander header icon
Q: Where do you manufacture copper hollow conductors?

A: Luvata's hollow conductors are produced in Pori, Finland. 

Q: Can you deliver the goods to our door?

A: For many locations around the world we can deliver the goods to customer's door. In certain countries nearest port or airport is possible.

Q: What is the lead time of copper hollow conductors?

A: The lead time is depending on the product. Typical lead times are 4-6 weeks from the order.

Q: Do you offer insulations on the hollow conductors?

A: Yes we do. Please contact our sales for more information.

Q: What is the MOQ (minimum order quantity)?

A: For several products we offer quantities starting from 50 kg

Q: Can you manufacture other sizes or shapes than listed on the tool list?

A: We can produce other sizes and shapes also. Please contact the sales for more details.

Q: What is the minimum bending radius of your hollow conductor?

A: Our customers are using 3 x width of the conductor as minimum radius. Some customers are using smaller radius occasionally.

Q: Do you also provide fittings to connect hollow conductors to cooling system?

A: Normally our customers are using their own solutions and therefore we do not supply fittings. 

Q: Where can I find the quality certificates for Luvata Pori? 

A: The quality certificates can be found both under Locations and in Document library   

  • lightning_

    Did you know?


    10 times more current
    Did you know that because of internal cooling, hollow conductors can carry over 10 times more current than solid conductors?
  • Mileon Giraffe_

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    Widest size range in hollow conductors
    Our capability in hollow conductor manufacturing starts from small conductors having the weight of 70 g/m and ends up to conductors more than 30 kg/m.
  • hollow conductor stator direct cooling

    Did you know?


    Electric vehicles just got cooler
    Luvata's hollow conductors are used for stator direct cooling in EVs. Learn more Greater-than sign image showing that the text is linking to another page.
  • iStock_000015090921Large_Japanese children

    Did you know?


    Every bit helps in finding a cure
    Copper has been used for medicinal purposes for thousands of years. Even today, at the beginning of the twenty-first century, its antimicrobial properties and intrinsic characteristic of very high electrical conductivity are underpinning a renaissance in healthcare and high energy physics.

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