P0 Capacitor, P2 Capacitor

Over-pressure protection (FPU): the Break-Action Mechanism (Type B/Class P2 capacitors)
Self-healing capacitors do not have to be separately fused against short circuits as they regenerate themselves after breakdowns of the dielectric. In the event of over-voltage or ageing at the end of the capacitor’s useful service life, an increasing number of self-healing breakdowns may cause rising pressure inside the capacitor. To prevent them from bursting, hermetically sealed capacitors can be fitted with a “break action mechanism”. This safety mechanism is based on an attenuated spot at one of the connecting wires inside the capacitor. With rising pressure the casing begins to expand, mainly by opening the folded crimp and pushing the lid upwards. As a result, the prepared connecting wire is separated at the attenuated spot, and the current path is interrupted irreversibly.

Over-pressure protection (FPU): the Break-Action Mechanism (Type B/Class P2 capacitors)
Self-healing capacitors do not have to be separately fused against short circuits as they regenerate themselves after breakdowns of the dielectric. In the event of over-voltage or ageing at the end of the capacitor’s useful service life, an increasing number of self-healing breakdowns may cause rising pressure inside the capacitor. To prevent them from bursting, hermetically sealed capacitors can be fitted with a “break action mechanism”. This safety mechanism is based on an attenuated spot at one of the connecting wires inside the capacitor. With rising pressure the casing begins to expand, mainly by opening the folded crimp and pushing the lid upwards. As a result, the prepared connecting wire is separated at the attenuated spot, and the current path is interrupted irreversibly.

95% of all critical capacitor failures are accompanied by a gradual increase of the loss power. As any increase of the loss power always leads to a temperature rise inside the winding element, the temperature fuse offers efficient protection for most of the critical capacitor failure scenarios. However, type A capacitors with temperature fuse can neither provide the kind of full protection offered by capacitors in aluminium can with break-action mechanism, nor can they fulfil the test requirements for such capacitors.

Important remarks on the safety of Type A and P0 capacitors
Type A capacitors do not have a specific failsafe device as specified in the applicable standards for type B- or P2-capacitors. In the event of failure the winding element may overheat rapidly and melt, smoke and even ignite; melted material may drip from the capacitor as well. It is therefore necessary to undertake proper measures to provide reliable safety for people and property when using type A capacitors. The recommendations of the German Association of the Electrical Industry (ZVEI) for the use of type A lighting capacitors say: Type A capacitors may be used in luminaires only where the capacitor is allocated (1) in uncritical environment (non-inflammable materials). In its Guidelines for the Prevention of Damage Caused by Luminaires, the Association of German Property Insurers – VdS – demands: Capacitors without overpressure break-action mechanism must be encapsulated in a metal case which prevents the ignition of inflammable materials in their (2) surroundings. Only capacitors with break-action mechanism are suitable for use in sensitive environment. In case of doubt regarding the character of the ambient conditions our capacitors with break-action mechanism should be given preference. 

CBB60 Capacitor  |  CBB61 Capacitor  |  CBB65 Capacitor  |  CBB80 Capacitor  |  CD60 Capacitor