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Capacitors are found in each and every variable speed drive and are one of the biggest causes of drive failure. They are used within drives to store electrical current and absorb the AC ripple to deliver a smooth DC voltage. Capacitors have a finite lifespan which we often see cut short due to two reasons - the environment the VSDs are installed in and lack of proper maintenance to counteract environmental impact.

What speeds up a capacitors deterioration?

One of the biggest causes of capacitor failure is overheating. This is because each capacitor contains liquid electrolyte which dries out over time. The liquid electrolyte drying out means that the ESR lowers until the capacitor blows, which can cause irreparable damage. Here at Northern Industrial, we have seen drives that have had big holes blown through the entire length of a drive due to one capacitor blowing.

How to prevent capacitor damage

Ensure adequate ventilation

One of the best things you can do to get the maximum lifespan of a capacitor, and therefore a variable speed drive, is to ensure the drive has proper ventilation. With proper ventilation, freely rotating fans and sufficient air flow through the drive, the drying out of the liquid electrolyte in the capacitor will slow down to a normal level.

Another important practice to prevent drives overheating and capacitors drying out is to ensure proper ingress protection for the environment the drive is installed in, as well as preventing dust and dirt building up in the drive. You can do this by vacuuming dust and dirt that may be clogged up in heatsinks, whilst the correct IP rating will protect the drive in the best way for the environment where it is installed. Keeping a drive clean and protected from ingress ensures sufficient airflow through the VSD.

Service your drives

It’s important to understand that no matter what you do and how perfect the operating conditions are for your drive, capacitors will have to be changed at some point due to their finite lifespan. Depending on the environment and whether it is harsh on your drive’s capacitors, it is recommended to complete a preventive maintenance service every five to eight years. 

In a preventive maintenance service, components like capacitors and fans will be replaced for new which prolongs the overall lifespan of the drive. Scheduled preventive maintenance for the internal components on drives also enables you to take the VSD out of production when it is convenient to do so, rather than rushing around under stress should the drive fail unexpectedly. Scheduled maintenance will also prevent damage such as blown capacitors which can damage other areas of the drive, ensuring a quicker turnaround than repair a fault or rebuilding damaged drives.

What happens if a capacitor does blow?

Sometimes despite best intentions a capacitor will blow and render a drive faulty. In this instance an industrial automation specialist like Northern Industrial is able to get you back up and running quickly. We can repair your drives down to component level and rebuild burnt out circuit boards and other problems. See below for some of the worst blown capacitors we’ve come across in our 40+ years of repairing automation parts. 

If you’d like to talk about scheduling your drives in for a service plan with us, or want more information about our VSD repair service, get in touch with our friendly team today.