APPLICATIONS GUIDE

1. Polarity: Type SWT Capacitors are of the polar design. Proper polarity must be maintained in circuit installation. No reverse voltage should ever appear across the capacitor, under any conditions.

2. Surge Voltage: The surge voltage rating of 115% of the D. C. rated voltage must not be exceeded. Voltages above the surge voltage can shorten capacitor life or result in catastrophic failure. The surge voltage limit must include the D.C. voltage plus the peak of any transient or ripple.

3. Ripple Voltage: The allowable A.C. ripple voltage is of particular importance in small electrolytic capacitors. The capacitor losses are defined as the equivalent series resistance (ESR). The A.C. current flowing through this resistance generates energy as heat by the expression: Watts= I2 ESR where I is the RMS A.C. Amps, and the ESR is related to the dissipation factor by the expression ESR = DFx104/ 2π fC , where f is frequency Hz and C is the capacitance in microfarads, and D.F. is % dissipation factor. The heat generated must be dissipated by the case surface without undue temperature rise. The allowable A.C. ripple voltage depends on the case size, the capacitance, the frequency, the D.C. rated voltage and the ambient temperature. The curves below provide convenient determination of the allowable A.C. ripple at 120 Hz and 25°C for each of the case sizes, with derating factors for the operation at higher frequencies and temperatures. The maximum ripple voltage at other frequencies is that which would produce the same allowable ripple current at 120 cycles.

NOTE: The sum of the D.C. voltage plus the peak A.C. voltage must not exceed the D.C. rated voltage. The D.C. voltage must be sufficiently high to ensure that the negative peak of the A.C. will not cause a voltage reversal on the capacitor.