When there is no room for BAM: Mesis®
The Mesis® safety concept was developed initially for low-inductance DC capacitors. E68 Mesis® makes it available for AC filter capacitors. The special low-loss and low-inductance design makes these capacitors particularly insensitive to high frequency harmonics and allows them to remain "cool" even with high operating currents.
Just like our tried-and-tested BAM fuses, the innovative Mesis® overpressure switch reacts mechanically to the internal pressure increase that is usually associated with the failure of film capacitors. As Mesis® - unlike the BAM device - does not require an external extension of the housing, the capacitor can be permanently installed and connected to rigid bus bars without impairing the function of the switch.
Unlike capacitors with BAM fuses, Mesis® capacitors do not disconnect themselves from the mains. Instead, the signal from the overpressure protection can be used on site or at a central detection point to immediately disconnect one or more affected capacitors. Particularly in filters, where a change in capacitance has an immediate effect on the resonant circuit and therefore on the filter frequency, the autonomous (and therefore initially unnoticed) disconnection of conventional BAM capacitors would sometimes lead to subsequent reactions due to altered filter behaviour or asymmetries. In contrast, the targeted transmission of a switch-off signal by Mesis® enables immediate corrective measures to be initiated, e.g. shutdown and maintenance.
Like our filter capacitors in the E62 family, the E68 Mesis® are also tightly sealed with metal cans and lids, providing excellent protection against environmental influences such as moisture and contamination from pollutants. Temporary condensation of these capacitor is therefore permissible. They also pass climatic tests under extreme conditions with 85%RH at 85°C. The sealed housing fulfils the requirements of hazard level HL3 in accordance with railway standard EN 45545 (fire behaviour of materials and components).