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Series-Resonant Inverter

Series-Resonant Inverter. Operation. T 1 fired, resonant pulse of current flows through the load. The current falls to zero at t = t 1m and T 1 is “self – commutated”. T 2 fired, reverse resonant current flows through the load and T 2 is also “self-commutated”.

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Series-Resonant Inverter

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  1. Series-Resonant Inverter ECE 442 Power Electronics

  2. Operation T1 fired, resonant pulse of current flows through the load. The current falls to zero at t = t1m and T1 is “self – commutated”. T2 fired, reverse resonant current flows through the load and T2 is also “self-commutated”. The series resonant circuit must be underdamped, R2 < (4L/C) ECE 442 Power Electronics

  3. Operation in Mode 1 – Fire T1 ECE 442 Power Electronics

  4. ECE 442 Power Electronics

  5. To find the time when the current is maximum, set the first derivative = 0 ECE 442 Power Electronics

  6. To find the capacitor voltage, integrate the current The current i1 becomes = 0 @ t=t1m ECE 442 Power Electronics

  7. ECE 442 Power Electronics

  8. Operation in Mode 2 – T1, T2 Both OFF ECE 442 Power Electronics

  9. t2m ECE 442 Power Electronics

  10. Operation in Mode 3 – Fire T2 ECE 442 Power Electronics

  11. ECE 442 Power Electronics

  12. ECE 442 Power Electronics

  13. ECE 442 Power Electronics

  14. Summary -- Series Resonant Inverter ECE 442 Power Electronics

  15. To avoid a short-circuit across the main dc supply, T1 must be turned OFF before T2 is turned ON, resulting in a “dead zone”. This “off-time” must be longer than the turn-off time of the thyristors, tq. The maximum possible output frequency is ECE 442 Power Electronics

  16. Series Resonant Inverter Coupled Inductors ECE 442 Power Electronics

  17. Improvement in performance • When T1 turned ON, voltage @ L1 is as shown, voltage @ L2 in same direction, adding to the voltage @ C • This turns T2 OFF before the load current falls to 0. ECE 442 Power Electronics

  18. Half-Bridge Series Resonant Inverter Note: L1 = L2 C1 = C2 ECE 442 Power Electronics

  19. This configuration reduces the high-pulsed current from the dc supply • Power drawn from the source during both half-cycles of the output. • Half of the current is supplied from the associated capacitor, half of the current is supplied from the source. ECE 442 Power Electronics

  20. Full-Bridge Series-Resonant Inverter ECE 442 Power Electronics

  21. Characteristics of the full-bridge inverter • This configuration provides higher output power. • Either T1-T2 or T3-T4 are fired. • Supply current is continuous but pulsating. ECE 442 Power Electronics

  22. Example 8.1 – Analysis of the Basic Resonant Inverter • L1 = L2 = L = 50μH • C = 6μF • R = 2Ω • Vs = 220V • fo = 7kHz • tq = 10μs ECE 442 Power Electronics

  23. Determine the resonant frequency The resonant frequency in Hz ECE 442 Power Electronics

  24. Determine the turn-off time toff ECE 442 Power Electronics

  25. Determine the maximum permissible frequency ECE 442 Power Electronics

  26. Determine the peak-to-peak capacitor voltage ECE 442 Power Electronics

  27. Determine the peak load current ECE 442 Power Electronics

  28. Sketch the instantaneous load current, capacitor voltage, and dc supply current ECE 442 Power Electronics

  29. Calculate the rms load current ECE 442 Power Electronics

  30. Using MATHCAD, Io = 44.1Amperes ECE 442 Power Electronics

  31. Determine the output power ECE 442 Power Electronics

  32. Determine the average supply current ECE 442 Power Electronics

  33. Determine the average, peak, and rms thyristor currents ECE 442 Power Electronics

  34. rms Thyristor Current Using MATHCAD ECE 442 Power Electronics

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