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EDITOR’S CHOICE A
n integral component within electric drive systems, a DBR converts excess energy generated during braking into heat, which it then safely dissipates to prevent the drive from overloading. For
high-power applications such as hoists, cranes, industrial machinery and railway systems, it is critical that DBRs can consistently and rapidly dissipate large amounts of energy. So, how can manufacturers ensure they select a suitable DBR for such demanding applications?
MATERIAL QUALITY IS KEY Since DBRs repeatedly process large amounts of kinetic energy, there is a risk that they could overheat. This could degrade materials over time or even create a fire hazard. To avoid this, it is essential that resistors are built to withstand high thermal stress and effectively dissipate energy at the required rate for the application. The resistive elements of DBRs are often made with stainless steel, as it is highly resistant to heat, corrosion and oxidation. With high chromium and nickel content, 304 and 316 grade stainless steel both have excellent resistive properties but the optimal stainless steel alloy varies depending on the application requirements. 316 grade contains two per cent
molybdenum, which makes it more resistant to deformation and degradation at high temperatures. For this reason, 316 grade is preferred for DBRs that need to operate under continuous, extreme heat exposure. However, 304 grade is a more cost effective alternative if the application does not involve continuous exposure to high temperatures.
EXTRA PROTECTION Resistance to corrosion is also an essential factor when selecting resistor materials. For example, DBRs within marine propulsion systems need to be strategically designed to prevent wear and degradation from exposure to moisture, salt and abrasion. High resistance to corrosion makes 316 grade an ideal choice for these harsh conditions, which is why it is often referred to as marine grade. To further enhance durability in marine environments, Cressall also uses titanium- sheathed elements in super duplex stainless steel vessels to ensure high, continuous performance even in hot sea water. In some industries, high-level sealing is
required. For instance, mining machinery is exposed to dust and debris that could damage the internal components. Enclosing the resistor elements from the surrounding environment is therefore essential for mining applications. The International Electrotechnical Commission (IEC) uses Ingress Protection (IP) ratings, made up of two numbers, to show how well equipment resists intrusion from solids like dust and liquids like water. Each number indicates the level of protection for that element. The first grades the level of protection against
OVERCOMING COMMON DYNAMIC BRAKING RESISTOR CHALLENGES
In the modern age of manufacturing, the operational efficiency and precise control of electric drives help to keep systems running smoothly. However, when an electric drive brakes, the excess energy generated must be carefully managed to prevent damage. This is where dynamic braking resistors (DBRs) come into play. Here, Mike Torbitt, managing director of resistor manufacturer Cressall, offers advice on overcoming some of the most common DBR challenges to ensure reliable performance, even for heavy-duty applications.
6 OCTOBER 2024 | FACTORY&HANDLINGSOLUTIONS
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