DEVELOPMENT OF ADVANCED METHODS FOR THE MEASUREMENT OF SOFT MAGNETIC MATERIAL CHARACTERISTICS

1. DEVELOPMENT OF ADVANCED METHODS FOR THE MEASUREMENT OF SOFT MAGNETIC MATERIAL CHARACTERISTICS Valentin PRICOP – TE-MSC-MNC

2. Magnetic Hysteresis Measurement - Epstein frame • Declared as the industry standard in magnetic parameters measurement. • Can be compared to an unloaded transformer • The current through the primary winding (green) is directly proportional to the magnetic field induced into the material (H) • Integral of the voltage collected from the secondary winding (red) is directly proportional to the magnetic induction (B) • The steel strips placed inside the coils affect the transformation ratio, therefore each material will show a specific B(H) dependency

3. Magnetic Hysteresis Measurement – BH curve - DC measurements • The variation of H is done at low frequencies 2-3 Hz • For lower frequencies the current is varied by using fixed value steps of sufficient amplitude to generate magnetic flux through the samples

4. Powering the frame – KEPCO bipolar power supply • First attempt to supply the frame was made with a KEPCO bipolar power supply ±36 V, ± 6 A Our problematic load Voltage loop – 50 Hz reference signal Current loop – 50 Hz reference signal Resistive load Current loop – 50 Hz reference signal Current loop – 50 Hz reference signal CH1 – Reference voltage CH2 – Supply output voltage CH3 – Current through the load CH4 – Voltage on the secondary of the “transformer”

5. Powering the frame – KEPCO bipolar power supply • Power supply set in voltage loop – 2 Hz reference signal Resistive load

6. Powering the frame – KEPCO bipolar power supply • Power supply set in current loop – 2 Hz reference signal

7. Powering the frame – CERN SMILE power converter Problematic load Voltage loop – 50 Hz reference voltage Current loop – 50 Hz reference voltage Resistive load Current loop – 50 Hz reference voltage Voltage loop – 50 Hz reference voltage

8. Powering the frame – CERN SMILE power converter Problematic load Voltage loop – 2 Hz reference voltage Current loop – 2 Hz reference voltage Resistive load Additionally, an lensed AC amplifier, class AB, was tested with similar results to the SMILE power supply.

9. SMILE or KEPCO Advantages of KEPCO: • Easy to handle and operate • Powered from 230 V Advantages of SMILE: • Negligible ripple • Very good response While the SMILE power converter would be the first choice for this application, due to its obvious advantages, the compatibility with this type of load still remains problematic.

10. SMILE power converter block diagram

11. 4Q Output Card View of the signals from the current measurement loop will help understand if the effect originates from this card, by indicating a current value higher then the actual one.

12. HF Inverter Control Card Scoping the gates of the switches during the occurrence of the glitch would reveal if there is any problem with the UCC3895 IC. Extract from UCC3895 datasheet. An 1.1 V hysteresis that would motivate the absence of current flow through the load after the 0 level crossing.

13. 4Q Control Card View of the command signal for the 4Q Power Card will help to eliminate this card as the source of the glitch.

14. Conclusions • Without clear identification of the problem we cannot order any other equipment, we would find ourselves facing the same problem. • Thanks to the documentation of the SMILE power converter, several tests could be made to better understand the origin of this glitch.

15. How can you help us? • Any suggestion regarding the origin of the glitch. • Assistance for scoping several test points on the different boards mentioned in the previous slides. • Devising a solution for a new power converter, after the source of the problem has been identified.