How to reduce the risk of capacitor failure in your UPS

Capacitors play a crucial role in a UPS system by helping to smooth, filter, and store energy. A typical uninterruptible power supply contains dozens of different types of AC and DC capacitors in both the main power section and at the printed circuit board (PCB) level.

UPS Capacitor failure will negatively impact the performance of a UPS System. Its filtering ability will suffer, there will be more issues with harmonics and electrical noise, the energy storage volume will reduce, and battery strings can be damaged. In the worst-case scenario, a serious capacitor failure will trigger the UPS to switch to bypass mode, which leaves the critical load unprotected.

Deterioration of AC capacitors can lead to:

• Increased inverter distortion
• Instability of the entire system (for parallel configurations)
• Sudden breakdown with fumes and noise disturbance, which could also damage other parts of the UPS
• Unscheduled machinery downtime
• Increased maintenance and repair costs compared to proactively replacing capacitors
• Unwanted damage caused by the capacitor exploding or the worst-case scenario of catching fire

There is no standard age at which a capacitor will fail. To ensure the ongoing performance and reliability of your UPS system, it is advisable to treat them as consumables and proactively plan their replacement before they reach the end of their rated service life. Most UPS Manufacturers recommended a time frame for this is between years 4 to 5 for capacitor replacement.

During regular Preventive Maintenance Visits (PMVs), field service engineers should visually inspect the capacitors to highlight any potential problems. Analysis of maintenance field readings will also help to identify the capacitors most likely to fail and allows you to plan a replacement before a failure causes unexpected downtime.

Source UPS can supply and fit AC and DC capacitors for all major brands of 3 phase UPS system. If you’re concerned that you’re uninterruptible power supply may need a capacitor replacement we offer one off health checks and have a range of annual UPS support and maintenance contracts which are proven to help extend the life of your UPS system and help reduce downtime.

To book a health check, or for more information on our support and maintenance plans, get in touch with Source UPS today!

Call: 01252 692559 or email: servicedesk@sourceups.co.uk