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F3063_C87 • 11/20/2015

7

Motor Run Capacitors

C87 Series, Cylindrical Aluminum Case, Overpressure Protection 420 VAC/470 VAC

Dissipation Factor

Dissipation factor is a complex function involved with the inefficiency of the capacitor. The tgδ may change up and down with increased

temperature. For more information, please refer to Performance Characteristics.

Sealing

Hermetically Sealed Capacitors

When the temperature increases, the pressure inside the capacitor increases. If the internal pressure is high enough, it can cause a

breach in the capacitor which can result in leakage, impregnation, filling fluid or moisture susceptibility.

Resin Encased/Wrap & Fill Capacitors

The resin seals on resin encased and wrap and fill capacitors will withstand short-term exposure to high humidity environments without

degradation. Resins and plastic tapes will form a pseudo-impervious barrier to humidity and chemicals. These case materials are

somewhat porous and through osmosis can cause contaminants to enter the capacitor. The second area of contaminated absorption

is the lead-wire/resin interface. Since resins cannot bond 100% to tinned wires, there can be a path formed up to the lead wire into the

capacitor section. Aqueous cleaning of circuit boards can aggravate this condition.

Barometric Pressure

The altitude at which hermetically sealed capacitors are operated controls the voltage rating of the capacitor. As the barometric

pressure decreases, the susceptibility to terminal arc-over increases. Non-hermetic capacitors can be affected by internal stresses due

to pressure changes. This can be in the form of capacitance changes or dielectric arc-over as well as low insulation resistance. Heat

transfer can also be affected by altitude operation. Heat generated in operation cannot be dissipated properly and can result in high RI2

losses and eventual failure.

Radiation

Radiation capabilities of capacitors must be taken into consideration. Electrical degradation in the form of dielectric embitterment can

take place causing shorts or opens.