Drive Braking Resistor Technology with Kanthal® Alloys

Content:

Applications of braking resistors
Types of electric resistance heating alloys
Top-notch production process
Advantages of Kanthal® alloys
Design factors influencing the operational life of electric resistance heating alloys
Braking resistors are used in
Braking resistors in wind power
The role of Kanthal® alloys in wind turbine braking resistors
Kanthal® electric resistance heating alloys in wind power applications — for long-lasting and outstanding performance

Applications of braking resistors

• Braking resistors are used where the speed of a motor exceeds the speed that is set through the variable frequency drive (VFD).
• Motor control systems to avoid hardware damage and faults within a VFD.
• In train systems and motor speeds.
• Operations where the motor controlled through the VFD acts as a generator and the power supply will be back to the VFD instead of to the motor. 
• To stop or slow down a motor by dissipating surplus voltage produced by the decelerating motor. 
• Motor-based applications which are controlled through the driver. 
• Motor braking, otherwise repairing by absorbing restored braking energy and dissolving it like heat through rheostatic resistors.

Types of electric resistance heating alloys

Praveen Gupta, Associate Vice President of Sales at Kanthal.Kanthal’s electric resistance heating alloys are categorized into two main groups based on their chemical composition: ferritic (FeCrAl) and non-ferritic aka austenitic (NiCr)+++.

"Ferritic alloys are inherently inductive, while austenitic alloys are the preferred choice when electric circuits require non-inductive materials. Moreover, for high-power needs in compact spaces, ferritic alloys are the best choice," explains Praveen Gupta, Associate Vice President of Sales at Kanthal. "Additionally, the lower the resistivity of an alloy, the better its voltage regulation capabilities," Gupta further notes.

These alloys boast stable electrical resistivity, with a change in temperature within a defined range, and can withstand temperatures up to 1425°C (2560°F). This makes them especially well-suited for braking resistors, where they outperform traditional resistance materials in terms of lifespan, energy efficiency, and reliability.

Our products are renowned for their exceptional reliability, beginning with the initial recognition of needs and culminating in guaranteed superior performance across diverse applications.

"Our comprehensive approach ensures that our products are renowned for their exceptional reliability, beginning with the initial recognition of needs and culminating in guaranteed superior performance across diverse applications," assures Gupta.

Top-notch production process

The production of Kanthal® alloys is a testament to advanced metallurgical engineering. From the precise alloying of ferritic and non-ferritic (austenitic) materials to the controlled melting and extrusion processes, each step is meticulously managed to produce alloys that meet exacting standards. This process ensures that the alloys exhibit the desired properties of resistivity, thermal stability, and mechanical strength, making them ideal for critical applications like braking resistors.

"Our integrated manufacturing facilities and R&D-driven processes are meticulously designed with the end application in focus, offering the widest range of alloys, each technically calibrated to align perfectly with international engineering standards," Gupta explains. 

Advantages of Kanthal® alloys

1. Higher Maximum Temperature: Kanthal® alloys can withstand temperatures up to 1425°C (2560°F). 
2. Increased Surface Load: Due to their ability to handle higher temperatures and longer lifespan, Kanthal® alloys support higher surface loads, enhancing performance and durability.
3. Wide Range of Resistivity: Kanthal® alloys exhibit stable resistivity, allowing for the use of elements with larger cross-sections. This not only improves the lifespan of the element, especially in thin wire applications but also offers considerable weight savings.
4. Superior Yield Strength: The higher yield strength of Kanthal® alloys reduces changes in cross-section during wire coiling processes, ensuring consistent performance.
5. Extended Lifespan: Kanthal® alloys typically last 2–4 times longer than other resistance alloys under similar conditions, significantly reducing maintenance and replacement costs.
6. Enhanced Oxidation Resistance: The formation of aluminum oxide (Al2O3) on Kanthal® alloys acts as an effective diffusion barrier, improves electrical insulation, and offers superior resistance in saline atmospheres.
7. Reduced Density: Kanthal® ferritic alloys’ lower density means more elements can be accommodated in the same space, leading to lighter components and cost savings.
8. Improved Corrosion Resistance to Sulfur: In environments with sulfuric compounds, Kanthal® ferritic alloys demonstrate superior corrosion resistance, making them ideal for harsh conditions.

"Kanthal® alloys deliver unmatched value, combining robust features and proven performance with exceptional cost efficiency. Our extensive sales and distribution network connects customers directly with our skilled engineers, ensuring access to top-tier application insights and proactive support for every project. We possess deep expertise in alloy application—from surface load and current capacity to temperature compatibility and atmospheric influences—empowering our clients with the knowledge they need for optimal alloy selection," Gupta asserts.

Design factors influencing the operational life of electric resistance heating alloys

The lifespan of electric resistance heating alloys depends on several key factors which vary by application. Here they are:

• Temperature & Temperature Cycling: High temperatures and frequent temperature variations significantly impact alloy durability.
• Contamination & Alloy Composition: Impurities and the specific composition of the alloy play critical roles.
• Physical Factors: Wire diameter, element geometry, surface condition, and mechanical stress also determine alloy longevity.
• Environmental Conditions: The atmosphere and the method of regulation tailored to the specific application are crucial.
• Oxidation Properties: Upon heating, resistance-heating alloys develop an oxide layer that protects against atmospheric attacks. For effective protection, this layer must be dense enough to resist gas and metal ion diffusion yet thin enough to adhere to the metal during temperature changes.
• Corrosion Resistance: Corrosive elements in the atmosphere significantly reduce wire life. Factors such as perspiration, mounting materials, and environmental contaminants contribute to corrosion. Specific environmental conditions also affect alloy performance:
• Steam and Halogens: These elements are particularly damaging, with halogens like fluorine and chlorine aggressively corroding high-temperature alloys at lower temperatures.
• Sulphur: Kanthal® ferritic alloys perform well in sulfurous oxidizing gases.
• Salts and Oxides: High concentrations of alkaline metal salts and boron compounds are detrimental.
• Metals: Contact with molten metals such as zinc, brass, aluminum, and copper should be avoided as they react with the resistance alloys.

Support and Installation considerations:

• Ceramic Support Materials: The choice of ceramic supports is vital, especially for high-temperature applications. Fire bricks should contain high alumina content, and iron oxide content should be minimized.
• Embedding Compounds: When using embedding compounds like ceramic fibers, materials such as alumina, alumina-silicate, magnesia, or zircon are recommended.

By understanding and managing these factors, the performance and lifespan of electric resistance heating alloys can be optimized, supporting the operational efficiency and durability of high-temperature applications. 

Braking resistors are used in

• Railway locomotives
• EOT cranes
• Lifts and elevators
• Metro rails
• Wind turbines

Braking resistors in wind power

Braking resistors have various applications across different sectors, including a pivotal role in wind power systems. In these systems, braking resistors are crucial for managing excess energy generated by the wind turbines during high wind conditions. The inclusion of resistance materials in these resistors is essential for maintaining the stability and efficiency of the turbines. This ensures that the turbines operate safely and effectively, preventing potential overloads and enhancing overall energy management.

The role of Kanthal® alloys in wind turbine braking resistors

Critical Energy Management

Kanthal® electric resistance heating alloys are essential in braking resistors for safely converting excess electrical energy into heat, especially during high wind conditions or grid anomalies. This capability is critical for protecting the turbine and electrical systems from overloads, ensuring continuous and stable operation.

Design Flexibility

Kanthal’s versatility in manufacturing allows for customized resistor material designs. Whether in wire or strip form, Kanthal® alloys can be adapted to meet specific design requirements, enhancing the overall efficiency of heat dissipation.

Integration with Wind Turbine Control Systems

Seamlessly integrating with wind turbine control systems, Kanthal-equipped braking resistors are crucial for real-time energy management, ensuring turbine reliability under dynamic wind conditions.

Kanthal® electric resistance heating alloys in wind power applications — for long-lasting and outstanding performance