ELECTRONIC FILM CAPACITORS, INC. Reidville Industrial Park * 41 Interstate Lane WATERBURY, CONNECTICUT 06705 PHONE (203) 755-5629 FAX (203) 755-0659 RESISTOR-CAPACITOR NETWORKS SERIES RC1313 APPLICATIONS Noise suppression and contact protection RL RN Vsource RL OR Vsource L CN RN Fig. 1 (across the load) CN L Fig. 2 (across the contacts) The circuit to be used is dependent upon particular situations. Either circuit may be enough protection for your needs. For extreme situations, both "Load" and "Contact" protection may be required. Recommendations There are two types of discharges that can damage switching contacts and generate noise: (1) "Glow Discharges" caused by the ignition of gases between contacts. These develop at about 320 volts at about a 0.0003 inch gap range and can be sustained at a much wider gap range. (2) "Arc Discharges" occur at much lower voltages, about 0.5 MV/cm. Minimum voltages and currents are necessary for "Arc Discharges" to be sustained. Contact material also plays a role in sustained "Arc Discharges". (see Table 1) MATERIAL MIN. (VA) MIN. (IA) Arcing Voltage Arcing Current mA Silver Gold Gold Alloy Palladium Platinum 12 15 9 16 17.5 400 400 400 800 700 The function of the RC network is to: (1) Keep the voltage across the contacts below 300 volts. C> (IL/300)2L (2) Keep the rate of voltage change below 1V/µs. C> IL x 10-6 (3) Keep the current below that described in Table 1. TABLE 1 Inductors do not instantly "let go" of a current. At the instant a contact opens, the current through the contact does not want to change. Using Ohms Law (E = IR), we can see that when the contact is closed, the resistance is essentially zero, making the voltage zero, as well. As the contact opens the resistance begins to increase. This leads to the generation of a high voltage which is generally destructive to contact life. Capacitors will restrict an instantaneous change in voltage. A capacitor, therefore is useful to counter the destructive voltages generated at the switch contacts. When the contacts are closed, the capacitor is out of the circuit. As the contacts are opened any change in voltage is restricted by the capacitor if its value is large enough to restrict the voltage change to less than 1 V/µs. A capacitor alone is not an ideal solution. When the contacts are open, the capacitor charges up to the supply voltage. As the contact is "made", an inrush of current results limited only by a residual resistance and damage may still result. For this reason, a resistor is configured in series with the capacitor. The higher the resistance value the smaller the inrush current and the less effective is the capacitor. The voltage across the contacts when opened is equal to the load current x resistance. (V = IR) It is recommended to keep V =< supply voltage. In this case, the maximum resistance of the network (RN) will be equal to the load resistance (RL). The above formulas are recommended for determining the RC network parameters. They do not identify all of the subtleties but should serve as a guideline for effective results. RESISTOR - CAPACITOR NETWORK NOMENCLATURE RC 1313 EFR - N - .1 - 6.3 - 20 / 5 101 RESISTOR VAL. (OHMS) DIELECTRIC CODE FIRST 2 DIGITS ARE SIGNIFICANT FIGURES - LAST DIGIT IS NUMBER OF ZEROS ADDED (i.e. 101 = 100 OHMS) CAPACITANCE 1313 - METALLIZED POLYESTER µ F) IN MICROFARADS (µ VOLTAGE CASE CODE TC - WRAP & FILL - ROUND - AXIAL TF - WRAP & FILL - OVAL - AXIAL EFR - EPOXY CASE - FLAT - RADIAL RES. WATTAGE 2 - 200 VDC 4 - 400 VDC 6.3 - 630 VDC SIZE CODE (SEE DIM. SPECS.) 2 - 1/4 WATT 5 - 1/2 WATT 6 - 1.0 WATT 7 - 2.0 WATT CAP. TOLERANCE 5 - 5% 10 - 10% 20 - 20% ETC. R/C NETWORK +_ .010" T L _+ .010" > EFC RC1313 R S +_ .025" L + .010" >< R > > EFC RC1313 H +_ .010" < < < < > > < 1.00 " MIN Insulated Leads (All dimensions in inches) DIMENSIONS AND RATINGS Cap. µF VOLTAGE DC AC RES. VALUE (OHMS) in. L T H mm in. mm in. mm EFC PART NUMBER 0.10 200 125 22-1000 .709 18 .295 7.5 .531 13.5 0.10 630 250 22-1000 1.04 26.5 .335 8.5 .669 17 RC1313EFR - N - .1 - 6.3 - _ / _ _ _ _ 0.25 200 125 22-1000 .709 18 .295 7.5 .531 13.5 RC1313EFR - H - .25 - 2 -_ / _ _ _ _ 0.25 630 250 22-1000 1.04 26.5 .394 10 .748 19 RC1313EFR - 0 - .25 - 6.3 - _ / _ _ _ _ 0.50 200 125 22-1000 1.04 26.5 .236 6 .591 15 RC1313EFR - L - .5 - 2 - _ / _ _ _ _ 0.50 630 250 22-1000 1.26 32 .512 13 .866 22 RC1313EFR - Q - .5 - 6.3 - _ / _ _ _ _ 1.0 200 125 22-1000 1.26 32 .335 8.5 .669 17 RC1313EFR - N - 1.0 - 2 - _ / _ _ _ _ 1.0 630 250 22-1000 1.26 32 .670 17 1.36 34.5 RC1313EFR - H - .1 - 2 - _ / _ _ _ _ RC1313EFR - V - 1.0 - 6.3 - _ / _ _ _ _ * Denotes UL recognized parts LEAD SPECIFICATIONS RESISTOR SPECIFICATIONS POWER (WATTS) VOLTAGE (VAC) TYPE 0.25 250 Carbon Comp. 0.50 250 Carbon Comp. RESISTOR TOLERANCE _+ 10 % or better (SOLID COPPERWELD) L (In.) S (In.) DIA. (In.) LEAD LENGTH (MIN. In.) .709 .562 .031 1.000 1.04 .886 .031 1.000 1.26 1.13 .031 1.000 EFC will manufacture to any non-standard value and size. Please consult factory for special requirements. * *