Posted on 11 April 2019

Mounting Positions of Aluminum Electrolytic Capacitors with Screw Terminals








During operation aluminum electrolytic capacitors always conduct a leakage current that causes electrolysis. On one hand, the oxygen produced by electrolysis will regenerate the dielectric layer but, on the other hand, the hydrogen released may cause increased internal pressure of the capacitor.

A safety vent in the can disk allows the gas to escape when the pressure reaches a certain level and prevents the capacitor from exploding in case of pressure increase due to an overload condition. To prevent electrolyte from leaking out when the gas has vented, the capacitor should not be mounted with the terminals (safety vent) upside down. The recommended mounting positions to avoid a vent-down installation of the capacitor are shown in the figure 1.

Recommended Mounting Positions for Aluminum Electrolytic Capacitor

Figure 1. Recommended range of mounting positions

Upright mounting is recommended, particularly when the capacitors are fixed by their terminals, by a threaded stud or near the base. In case of horizontal mounting, the safety vent should be at the "12 o'clock" position.

Mounting positions other than recommended will not cause any direct damage to the capacitor but may result in serious consequential damage in the application during operation due to electrolyte leakage in the case of venting.


For more information, please read:

Capacitor Bank Design

Calculating the Useful Life of Capacitors

Film Capacitors for DC-Link

Equivalent Series Resistance (ESR) for Capacitors


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