Capacitor life expectancy: How to avoid an early demise
Let’s start with a reality check: electrolytic capacitors have a limited lifespan due to the evaporation of their electrolyte. Sure enough, other power supply components such as fans and switches can fail over time, but one factor sure to cause premature downtime is partnering with a power supply manufacturer that has failed to take account of the potential for electrolytic capacitor failure.
Although manufacturers of electrolytic capacitors specify design lifetime at the maximum rated ambient temperature, power supply manufacturers must do more to maximise longevity.
The first step is to fully assess the operating environment. Today we see power density on the rise, influenced by factors that include the ever-burgeoning density of data centre racks, super-fast demand forartificial intelligence (AI) and the quickening paceto market of electric vehicles. Higher power density– particularly in combination with ever-smaller form factors–accelerates wear on electrolytic capacitors because it typically leads to increased operating temperature and ripple current.Both of these effects negatively impactcapacitor lifespan, demanding a response from power supply OEMs.
Heat emanates both from internal components and external sources, such as nearby machinery. For a power supply manufacturer, considering the potential extremes of these factors is paramount in the design or specification of a remediating cooling system.
An optimised cooling system can manage capacitor integrity by minimising the impact of heat on its operating life. Notably, power supplies that incorporate enclosed cooling fans are more reliable in high power density applications due to theircloser proximity to heat-generating components.
But the deployment of cooling fans is only half the job. Adequate clearance between fans and components is also necessary to ensure proper airflow. Any failure in this regards can restrict airflow and assist rather than mitigate potential overheating.
It's also necessary to consider ripple current, which in a switch-mode power supply results primarily from incomplete suppression of the AC waveform after rectification. This subsequently creates power dissipation within electrolytic capacitors. As ripple current is unavoidable, the goalwhen designing apower supplyshould be minimisation.
The power supply's topology, switching frequency and component characteristics are the primary defining factors in determining the magnitude and frequency of ripple current. Minimising this unwanted effect relies on the power supply OEM’s knowledge and experience in filtering techniques, advanced rectifier designs and voltage regulation.
Useful things to know about Mascot’s blueline Battery Chargers and Power Supply Units:
- only use passive natural convection cooling (don’t need other cooling methods, such as conduction to external heat sinks or fans which may emit audible noise and include mechanical parts which may fail)
- don’t use mechanical switches which may wear out
- All our electrolytic capacitors have minimum 5 years verified guaranteed lifetime, when charger/PSU is operated at full rated load at 30 °C ambient temperature.
Ultimately, many would make a case for electrolytic capacitors as the components most likely to cause power supply downtime. So, if you’re about to specify a power supply for your new product or system, cross-referencing factors like integrated thermal management, fan clearance and countering the effects of ripple current will go a long way to maximising service life.
Of course, the temperature rises typical of the power supply’s end-use application will also bear huge influence. Further factors include mounting orientation, positioning, surrounding space, applied load and more. A reputable power supply manufacturer can work with product design engineers to determine the optimal solution.