Prof R T KennedyEMC & COMPLIANCE ENGINEERING 1 EET 422 EMC & COMPLIANCE ENGINEERING
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 2 AC SOURCE FILTER EUT large attenuationnegligible attenuation at line frequency High Frequency LOW Frequency FREQUENCY RESPONSE Low Pass High Frequency large attenuation
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 3 CX CY L N G L* N *N * G* L L M EUTEUT AC source ‘X’ capacitors connected line – neutral for differential mode (symmetrical) interference mitigation ‘Y’ capacitors connected line-ground neutral-ground for common mode (asymmetrical) interference mitigation
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 4 CX CY L N G L* N *N * G* L L M EUT AC source
IMPEDANCE to DIFFERENTIAL MODE EMISSIONS Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 5 L-M i dm M
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 6 CX CY L N G L* N *N * G* L L M EUT AC source X capacitors: NO restriction on value typical 0.1 μF → 1.0 μF 3 classes of TYPE ‘X’ capacitors X2 most common X TYPE applications when capacitor failure will not lead to a dangerous electrical shock
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 7 CX2 CY2 L N G L* N *N * G* L L M EUTEUT AC CX2 CY2 L N G L* N *N * G* L L M EUTEUT AC
COMMON MODE INDUCTOR Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 8 DM differential mode current common mode current CM L N G
IMPEDANCE to COMMON MODE EMISSIONS Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 9 L+M i cm M
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 10 CX CY L N G L* N *N * G* L L M EUT AC source 4 classes of TYPE ‘Y’ capacitors Y2 most common Y CAPACITOR LEAKAGE CURRENT to GROUND UNDESIRABLE for SAFETY REASONS ‘Y’ CAPACITORS CANNOT B BE REMOVED ESSENTIAL for effective emi filtering ‘Y’ TYPE applications when capacitor failure could result in a dangerous electrical shock
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 11
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 12 CX CY L N G L* N *N * G* L L M EUT AC source 50 Hz leakage current → ground MUST BE LIMITED medical applications: 50 A limit other applications: 0.5 mA limit
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 13 CX CY L N G L* N *N * G* L L M EUT AC source TYPE ‘Y’ capacitors generally restricted to SMALL values typically 470 pF medical applications 4700 pF other applications TYPE ‘Y’ capacitors have limited capacitance and enhanced electrical and mechanical reliability
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 14 CX CY L N G L* N *N * G* L L M EUT AC source smaller CY capacitors reduce leakage current smaller CY capacitors reduce filter CM insertion loss good for safety bad for EMI
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 15
AC LINE CAPACITORS “self healing” impregnated metallised paper “self healing” metallised film Ceramic do not self heal and tend to be larger than the other types Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 16
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 17 ‘Y’ TYPE IMPREGNATED PAPER 240 V 50 Hz C Tolerance TEMPERATURE STABILITY T (min o C)T (max o C) ± y1 %- a1 %+ b1 % ‘Y’ TYPE TYPICAL PARAMETERS IMPREGNATED PAPER 240 V 50 Hz C Tolerance TEMPERATURE STABILITY T (- 40 o C)T (+ 100 o C) ± 20 %- 3 %+ 8 %
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 18 CAPACITANCE on COMPONENT NOT the ACTUAL VALUE: TOLERANCES ! MAXIMUM LEAKAGE CURRENT determined by MAXIMUM CAPACITANCE
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 19
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 20 IMPORTANT for EMI CM EMISSION LEVEL NOT a SAFETY ISSUE
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 21 ‘Y’ TYPE CERAMIC 240 V 50 Hz C Tolerance STABILITY T (min o C)T (max o C)AC voltageageing ± y2 %- a2 %+ b2 %+ c %0 % - d % ‘Y’ TYPE CERAMIC TYPICAL PARAMETRS 240 V 50 Hz C Tolerance STABILITY T (- 40 o C)T (+ 100 o C)AC voltageageing ± 20 %- 15 %+ 15 %+ 30 %0 % ; - 10 %
MORE PARAMETERS AGEING : instability over time AC VOLTAGE STABILTY Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 22
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 23
Prof R T Kennedy EMC & COMPLIANCE ENGINEERING 24 IMPORTANT for EMI CM EMISSION LEVEL NOT a SAFETY ISSUE