Presented By:Nitish Dubey

Under the guidance and supervision of

Dr. Anita Seth Mr. Praveen Kr. Agarwal Assistant Professor, SO/F, IET-DAVV LSES, RRCAT

Study and reduction of conducted emissions generated by switch mode power supply to

trigger thyratron switch used in high voltage pulse generation

Content

Aim of Project Need of Project Literature Review Conducted Emission Standards Power Supply Instrumentation used for Measurement Conducted Noise Measurements of Trigger Unit EMI Filter Calculation of LCM, LDM, CX & CY Results Conclusion

Aim of Project

To study the conducted emission generated by trigger power supply.

Design of EMI filter to reduce the Conducted emissions of Trigger Power Supply.

What are Conducted Emissions?

Need of Project

The primary reason to study and regulate conducted emissions is to reduce electromagnetic energy that is coupled to a product’s power cord and find its way to the entire power distribution network.

These emissions effect the output and performance of all devices connected to that power distribution network in which they are present.

Range of radio frequency disturbance 10 kHz to 30 MHz conducted emissions30 MHz to 1 GHz radiated emissions

Literature Review

“Conducted Emissions Testing For Electromagnetic Compatibility” P.V.Y. Jayasree et.al., “EMI Filter Design for Reducing Common-Mode

and Differential-Mode Noise in Conducted Interference” Agrawal P.K., B.P.Das, Nakhe S.V., “Conducted Noise Studies of High

Voltage Pulsed Power Supply for Copper Vapor Laser -A case Study” “Characterization and Parasitic Extraction of EMI Filters Using

Scattering Parameters” “Separation of common and differential mode conducted emission:

Power combiner / splitters” “Modeling and Design of EMI Noise Separators for Multiphase

Power Electronics Systems”

Conducted Emission Standards

The standards are first made by CISPR committee. These EMC standards are adopted by governmental regulatory

agencies around the world like FCC (USA), BSI (British Standard Institute), VDE (Germany), EN (Euro-Norms), VCCI (Japan) etc.

The standards are again classified as Class A (Products used in establishment other than domestic areas) and Class B (Products suitable for use in domestic establishments).

The power supply used is a trigger unit.

This power supply is very critical for operation of Thyratron switch.

This power supply is operated in two modes internal mode (INT, internal oscillator) and external mode (EXT, through fiber optical cable or electrical signal).

This power supply is chosen for our study as it generates lot of conducted emission.

Power Supply

Instruments used for conducted noise measurement

1. LISN (Line Impedance Stabilizing Network)LISN prevents the noise generated by EUT to enter into the mains which may affect the other equipment connected on the same mains.

2. SA (Spectrum Analyzer)Spectrum analyzer is used to displays the spectral distribution of noise voltage with respect to frequency or RF energy. Spectrum analyzer works on super-heterodyne principle.

CONDUCTED NOISE MEASUREMENTS OF TRIGGER UNIT

Measurement Setup

CONDUCTED NOISE MEASUREMENTS OF TRIGGER UNIT

Actual photograph of test setup used to test trigger unit

Noise during internal mode of operation

CONDUCTED NOISE MEASUREMENTS OF TRIGGER UNIT

Average Quasi Peak

CONDUCTED NOISE MEASUREMENTS OF TRIGGER UNIT

Separation of CM and DM noise from total noise in INT mode

From the above graph we can see that CM noise is greater than DM noise So, first we design CM filter.

EMI Filter

Circuit diagram of EMI filter with LISN

Equivalent circuit of CM filter in AC line Equivalent circuit of CM filter in AC line

Calculation of LCM, LDM, CX & CY

IL (required) = V noise (dBµV) – V limit (dBµV)

IL for CM filter is 30 dBµV at 350 kHzIL for DM filter is 20 dBµV at 150 kHz

CY = 1.1 nF (two 2.2 nF capacitors are in series) acc. to standard IEC950.

LCM = 3.17 mH at 62.23 kHz

L leakage = L DM = 200 µH

CX = 72 nFFor high attenuation we choose CX = 100 nF.

Results

Average Quasi peak

Results

CM Noise DM Noise

Conclusion

EMI filter design for common mode and differential mode filter was taken up and implemented.

The insertion loss was more by 40 dBµV at 350 kHz frequency for CM and 25 dB at 150 kHz for DM.

The conducted noise generated by trigger unit is reduced to below limit line of EN 55011 class A (average)