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Rated Capacitance (CR) This is the designed value of capacitance, usually specified in micro-Farads (µF).when measured with an a.c. voltage <0.5V at 100Hz and 20°C, withno bias voltage applied. The value of capacitance decreases with frequency and increases with temperature, the magnitude of variation being dependent on the capacitor type. Capacitance Tolerance Due to material and manufacturing process variability a tolerance is specified for the rated capacitance. For a typical batch of capacitors the distribution of capacitance values is generally within ±5% of a nominal value. back to top Rated Voltage (UR) The rated voltage is the value of voltage that may be applied continuously, within the operating temperature range of the capacitor. Generally the rated volatge and category voltage have the same temperature. back to top Surge Voltage Unless otherwise stated in the data sheets capacitors shall withstand 1000 cycles at upper category temperature as described below: Charge to surge voltage and hold for 30 seconds followed by a no load period of 5.5 minutes with the capacitor disconnected and allowed to discharge internally. The power supply used shall be capable of delivering >5 A at the test voltage. Short duration surge voltage - certain product ranges are able to withstand a higher surge voltage but for a shorter period of time. Where applicable these capacitors shall withstand 100 surges at 20°C as described below: Charge capacitor to rated voltage then charge up to short duration surge voltage for a period of <500 mS then discharge completely, followed by a no load period of 5 minutes. Figures for this test, where applicable, are shown under the range data sheets. back to top Voltage Proof (For sleeving and end discs) Values are quoted for each range in the data sheets. These values are applicable to insulating sleeves and end discs in good condition with no scuffs or scratches. Damage caused by improper handling may reduce these values. The test involves applying a high d.c. voltage, i.e. 2500V, across the insulating sleeve of the capacitor for a period of 1 minute. During this test period there should be no sign of breakdown or flashover. back to top Dissipation Factor The dissipation factor or tangent of the loss angle (tan d)is a measure of the deviation from that of an ideal capacitor, and is related to the capacitance and e.s.r. values as follows:-  Where C and e.s.r. are at frequency f. back to top |