1. Presented by: Lesedi Masisi
The Effect of the Three level Neutral Point Clamped Inverter on the Core Loss of a Synchronous Reluctance Machine
Presented by: Lesedi Masisi
School of Electrical and Information Engineering
University of the Witwatersrand
1 Jan Smuts Ave, Johannesburg, 2000
Maged Ibrahim
John Wanjiku
Akrem M. Aljehaimi
Pragasen Pillay
The Department of Electrical and Computer Engineering
Concordia University
Montreal, Québec H3G 1M8
2018

2. Table of Contents Why a Three Level Inverter? Test Bench
Core Loss Measurement Methodology
SynRM Drive
Experimental Results A
Core Loss: Considering Inverter Switching Effects
Experimental Results B
Conclusion

3. Why a Three Level Inverter?
Demand for higher voltage
Uses four switches in a leg
Lower rated power devices
Lower THD
Challenges
Balanced capacitor voltages
Suppressing neutral point voltage ripple

4. Why a Three Level Inverter?
Most work has been on the inverter
Inverter losses and modulation schemes
Effects of three level inverter on the SynRM
Core losses
Comparison between 2-level and 3-level inverter SynRM drives
Standards
No existing standards for inverter fed machines

5. Test Bench Matlab/Simulink software High bandwidth amplifier
dSPACE
Inject flux density waveform into stator toroid
High bandwidth amplifier
Power source
36 slot stator toroid
Wounded with 36 and 72 turns
High frequency (36 turns): 30 Hz
Low frequency (72 turns): 60 Hz
Primary and secondary sides

6. Core Loss Measurement Methodology
Conventionally
Epstein frame
Laminations
Material deformations
Extraction of the current waveforms under load

7. Core Loss Measurement Methodology…cont
The SynRM coupled to a dc generator
Operated at the optimal current angle

8. Core Loss Measurement Methodology…cont

9. Core Loss Measurement Methodology…cont

10. Core Loss Measurement Methodology…cont

11. Core Loss Measurement Methodology…cont

12. Core Loss Separation Method
Core losses = Hysteresis + Eddy Current loss
Hysteresis loss per cycle
Core loss measurements at low frequencies
By extrapolation of total core loss
At zero frequency the core losses represent the hysteresis loss per cycle

13. Core Loss Separation Method
Hysteresis loss per cycle
Assumed independent of frequency
Minor loops are considered negligible

14. Experimental Results A
Stator tooth flux density excitation
At 30 Hz

15. Experimental Results A…cont
Stator tooth flux density excitation
At 60 Hz,

16. Experimental Results A…cont
Stator tooth flux density excitation
At 180 Hz,

17. Experimental Results A…cont
Table 1A: Stator tooth eddy current loss (%)
Table 1B: Stator yoke eddy current loss (%)

18. Experimental Results A…cont
Stator tooth B-H 180 Hz, (i) 2-LINV and (ii) 3-LINV
Stator yoke B-H 180 Hz, (i) 2-LINV and (ii) 3-LINV

19. Core Loss: Effects of Inverter Switching
Experimental Set-up

20. Experimental Results B

21. Experimental Results B…cont

22. Experimental Results B…cont

23. Conclusion Core losses of 2 and 3-LINV SynRM were compared
FE software was used to compute the flux density waveforms
Stator core excited with maximum flux density of 1.5 T
At 30 Hz, 60 and 180 Hz
3-LINV SynRM drive (Core loss separation)
More than 9% lower eddy current loss on the stator tooth
Approximately 7% lower eddy current loss desity on stator yoke
Core losses on stator tooth lower as compared to stator yoke
Stator tooth harder to cool as compared to the yoke
The use of 3-LINV will contribute towards reducing the burden of the cooling system

24. Acknowledgement

25. Thank you