V I S H AY I N T E R T E C H N O L O G Y, I N C . www.vishay.com Capacitors Application Note AC Film Capacitors in Connection with the Mains Because of the high energy availability and the severe environment of surge voltages and pulses, applications of capacitors in connection with the mains must be chosen carefully. Two kinds of connections and thus two kinds of applications can be distinguished. One is where the capacitor is directly connected in parallel with the mains without any other impedance or circuit protection, and another where the capacitor is connected to the mains in series with another circuitry. CAPACITORS DIRECTLY CONNECTED IN PARALLEL WITH THE MAINS WITHOUT ANY OTHER IMPEDANCE OR CIRCUIT PROTECTION (ACROSS THE LINE OR X CLASS CAPACITORS) To help reducing emission and increasing the immunity of radio interference, electromagnetic interference suppression film capacitors (EMI capacitors) are playing a major role in all kind of applications. These capacitors are put directly parallel over the mains at the input of the appliances. L Application N CX Several functions are combined in these small components: Excellent high frequency properties for short circuiting radio interference, being continuously stressed by the AC mains voltage and not at least having the ability to sustain transient voltages, caused by for example lightning strikes, switching, superimposed on this line. For EMI capacitors it is a very difficult job to keep fulfilling the stringent requirements for safety and at the same time to COUNTRY miniaturize for offering customers benefits in terms of costs, functionality and mounting possibilities. Five main characteristics can be seen for EMI-capacitors: • Excellent capacitive filter: Low inductance and equivalent series resistance are preferred • Withstanding pulse loads: Uncontrolled mains switching must be sustained • Continuous biased by the mains voltage: A powerful energy supply is always available • Withstanding surge voltages: High energy surge voltages could destroy the capacitors • Safe end of life behavior It has been noted by several national authorities that safety is top priority for these components. Therefore international safety standards have been developed like IEC 60384-14 (world standard) and UL 60384-14 (US standard). National authorities prescribe that EMI capacitors to be connected directly in parallel with the mains must be proved to fulfill these standards. Approved products receive safety certificates and are allowed to have following safety marks: SAFETY STANDARD UL 60384-14 Canada CSA E384-14 U.S.A. and Canada Combination Mark (UL 60384-14 + CSA E384-14) China CQC Europe EN 60384-14 and IEC 60384-14 Revision: 26-Jul-13 Document Number: 28153 1 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 APPLICATION NOTE U.S.A. APPROVAL MARK Application Note www.vishay.com Vishay AC Film Capacitors in Connection with the Mains Based on many years of experience Vishay has brought several EMI product series fulfilling these strong safety standards for across the line applications. Depending on the customer's application needs following product series are recommended: CLASS X2 X1 VOLTAGE 310 VAC 480 VAC Standard across the line applications, stability grade as per IEC 60384-14 (1) MKP336-2 MKP338-2 MKP338-4 MKP339 F339MX2 F1778 MKP338-1 F339X1 330VAC F1772 F339X1 480VAC For continuous (2) across the line operation, higher stability grade than per IEC 60384-14 (1) Notes (1) IEC 60384-14 endurance test conditions require ± 10 % capacitance change after 1000 h testing (2) Continuous in the meaning of uninterrupted connected to the mains, 24 h/day during several years CAPACITORS CONNECTED TO THE MAINS IN SERIES WITH ANOTHER CIRCUITRY (SERIES IMPEDANCE APPLICATION) In many appliances a low voltage supply is needed for simple low energy consuming functions like sensing, phase detection,… To reduce the voltage, reactive impedances are used like film capacitors. L CS R Low Energy Consuming Applications APPLICATION NOTE N In this case the capacitors are connected in series with the application to the mains and now the functions to be fulfilled are: • Stable voltage dropper: A stable capacitance must be guaranteed over the total lifetime of the application • An adjusted tolerance: To guarantee a well defined current supply • Continuous biased by almost the mains voltage: Internal ionization must be avoided But what about withstanding surge voltages? And what about safety? As these caps are connected through another circuitry, the equivalent impedance of this circuit can protect the capacitor. A film capacitor could be destroyed when a high WITHOUT SAFETY APPROVALS (1) CLASS VOLTAGE Standard and continuous energy pulse is applied and the self healing properties are failing (self healing is the ability to recover after a breakdown). As general rule for standard capacitors, not approved according international standards for EMI capacitors, this can happen if surges occur higher than the guaranteed proof voltage. This is in general 1.6 times the rated DC voltage or 4.3 times the rated AC voltage. As it is generally accepted that surge voltage (1.2 μs rise time/50 μs duration) can occur at the entrance of appliances being 2.5 kV for installation category II and 4 kV for installation category III (IEC 60664-1), it must be verified by the customer that the impedance in series with the capacitor limits the over-voltage to these values. In general this will be the case because it can easily be calculated that equivalent impedances will be in the range of 220 to a few k depending on the low voltage application and by this the surge will be topped off to a few hundred volts maximum. In all other conditions still an approved safety component must be used, but here the extra functions as stable capacitance and adjusted tolerance must be fulfilled as well. This can only be guaranteed by a different capacitor construction wherein two capacitor sections are internally connected in series. Also for these series impedance applications Vishay can offer a wide range of products fulfilling customer's needs and requirements: (2) in series with the mains operation WITH SAFETY APPROVALS 275 VAC 310 VAC 480 VAC (3) F1772 F339X1 480VAC Notes (1) The applicant must guarantee that the maximum continuous mains voltage is lower than the rated AC voltage and that maximum temporary over-voltages (< 2 s) are lower than 1.6 rated DC voltage or 4.3 times AC rated voltage. Instructions can be found in the application notes and limiting conditions in the detail specifications. (2) Continuous in the meaning of uninterrupted connected to the mains, 24 h/day during several years (3) For the right choice of the component, contact [email protected] Revision: 26-Jul-13 Document Number: 28153 2 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 Application Note www.vishay.com Vishay AC Film Capacitors in Connection with the Mains CAPACITORS DIRECTLY CONNECTED IN PARALLEL BETWEEN THE MAINS AND GROUND (LINE BYPASS OR Y CLASS CAPACITORS) To help reducing common mode electromagnetic interference, capacitors are connected between mains and ground. For these applications only approved safety components are allowed. Different safety classes and standards are defined in the same IEC 60384-14 and UL 60384-14 standards. L Application CX N CY Vishay has following products in its film capacitor portfolio, adapted for the specific customers need: CLASS Y2 VOLTAGE 305 VAC Standard line bypass applications F1710 MKP338-6 Line bypass application for continuous operation (1) MKP338-6 APPLICATION NOTE Note (1) Continuous in the meaning of uninterrupted connected to the mains, 24 h/day during several years Revision: 26-Jul-13 Document Number: 28153 3 For technical questions, contact: [email protected] THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000