• • • SAFETY IN ENGINEERING • • •
Increasing resistor reliability Maintenance tips to get the most from your resistor
rom railways to renewable energy, to marine applications and motor control, resistors are an essential component of many electrical and mechanical systems. But failing to keep your resistors in good condition can threaten their reliability, resulting in reduced functionality and safety issues. Here, Mike Torbitt, managing director of resistor manufacturer Cressall, offers advice on how to extend resistor lifespan. Resistor technology is constantly evolving, with innovation in materials and design leading to improved performance and new industry applications. Without these components, many of the renewable technologies needed to meet net- zero targets would be unviable. For example, dynamic braking resistors (DBRs) safeguard battery electric vehicle (BEV) engines that use regenerative braking systems by dissipating surplus electrical energy as heat. Likewise, DBRs also support energy output in renewable applications such as tidal power, wind turbines and motorised solar panels. However, damaged resistors put strain on the entire system, risking decreased efficiency and reduced lifespan for both the resistor and other components. A damaged resistor may experience a reduction in its stated resistance value, which takes it beyond the specified tolerance range. This
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means that under normal operating conditions, the resistor will not be able to regulate electricity flow effectively. Reduced resistance often results in voltage spikes and in some cases, complete circuit failure. In high-voltage and high-power applications, these failures can have serious consequences, causing safety hazards such as electric shocks and even fires. Understanding the key reasons behind resistor degradation allows you to safeguard your application against them and extend resistor lifespan.
Keeping dry
Data from HSB shows that moisture is responsible for 17.4 per cent of electrical failures, making it the second biggest cause after loose connections. Moisture presents a particular challenge in tidal and maritime applications as the chlorides present in sea water can corrode and damage the resistor. Selecting the right material for your resistor is essential in protecting it against salt water corrosion. Opting for a resistor that is manufactured from 316 grade stainless steel offers better resistance to chlorides when compared with other materials due to its chromium content of over 10.5 per cent. Not only can a higher grade of steel protect the resistor against salt water damage, but it is also preferable for systems that
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will be exposed to other harsh chemicals such as chlorine and acids.
Electrical enclosures are also an important consideration in reducing moisture exposure. The IP system, where the first digit refers to dust protection and the second to liquids, allows you to choose an appropriate level of defence against moisture. The higher the second digit, the higher the level of protection against liquids it offers. Although corrosion often takes place in more gruelling environments, it can also occur in land- based applications. Ensuring resistors are stored in a clean and dry environment before they are used within an application is essential to tackling this issue.
Handling the heat
When a resistor becomes coated in dust or dirt, it is more prone to overheating due to a compromised ability to dissipate heat effectively. Overheating can damage the resistor’s internal components and presents a fire risk. This thermal stress can in turn lead to mechanical stress, wherein the resistor becomes worn due to excessive strain. Mechanical stress can be decreased by avoiding excessive bending or tension on resistor leads when assembling the system.
electricalengineeringmagazine.co.uk
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