Drives & Controls September 2022

43 www.drivesncontrols.com September 2022 SERVICE AND REPAIRS n Keeping your inverters clean can avoid headaches A major factor responsible for the premature failure of inverters is environmental issues that lead to overheating. This can affect the electrolytic capacitors are found in most industrial electronics, particularly inverters, where they are used in the internal power supplies, DC links and firing stages. Manufacturers quote the lifetimes of these components from as little as 1,000 hours to more than 10,000 hours at their maximum rated temperature (usually 85°C or 105°C). For each 10°C reduction in temperature, the expected lifespan of an electrolytic capacitor can double. This can mean that a capacitor with a quoted life of 5,000 hours at 85°C could have its lifespan increased to 40,000 hours by keeping its operating temperature below 55°C. For an inverter working 10 hours a day, this could mean the difference between failing after just 500 days, or after 4,000 days. A failing inverter can cause issues further downstream on an installation. For example, misfiring output stages can lead to excessive currents in motor windings and premature motor failures, while erratic control of the motor can cause mechanical or production issues, leading to unexpected costs. To give an inverter the best chance of achieving a long life, it will need routine maintenance – in particular, cleaning. Firstly, pay attention to the area where the inverter is installed to ensure that the ambient conditions are optimum. If it’s in a panel, are the panel doors closed? Do the panel fans work and are filters fitted and clean? Panel filters should be cleaned or replaced as necessary, which will vary greatly, depending on the area in which they are installed. On the inverter itself, is the heatsink clean and dust-free? Are the fans free to rotate? The heatsink and installation are designed to allow sufficient air flow to keep the inverter operating at an reasonable temperature. Fibres, dust and dirt can all clog the heatsink and fans, reducing the airflow to fractions of the required level. Also check whether all the power terminals are tightened correctly? Incorrectly tightened power terminals can lead to local hotspots. They can be inspected using a thermal camera as part of a thermal analysis regime. Finally, are all parts of the case in place? Internal fans on the control boards and power supply boards on some drives rely on covers being in place to achieve the correct airflow. Some manufacturers recommend replacing heatsink fans as often as once every three years – and more frequently if the drives are operating in harsh conditions. In such cases, the fans can often be replaced easily by the end-user, but on many drives, replacement will require some degree of disassembly. Regardless of all the measures taken, at some point in their lives, drives will benefit from a thorough overhaul. This involves replacing all of the electrolytic capacitors on the drive, and cleaning it thoroughly. This is a task usually undertaken by specialists and is not recommended to be attempted by end- users. Taking a proactive approach to ensuring drives (and the environment in which they operate) are kept clean can avoid huge headaches further down the line. Adopting an attitude that involves cleaning drives before they get dirty, and also reducing their chance to pick up dirt through a holistic approach to the operating surroundings, is the best way to maximise efficiency and to minimise downtime. n Keeping your inverters clean can avoid downtime – not only from failing inverters needing to be replaced, but also from mechanical damage resulting from the failure leading to major replacement costs and extended production downtime. Steve Turner, service manager at Northern Industrial, explains how to do this. Clogged heatsinks and fans can lead to drives overheating and failing prematurely