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GOOD AFTERNOON !

GOOD AFTERNOON !. Power electronics converters applications and motors. Chethan raj.D 2 nd sen M.tech,caid. CONTENTS. INTRODUCTION DIFFERENT TYPES OF CONVERTERS UNCONTROLLED RECTIFIERS CONTROLLED RECTIFIERS APPLICATIONS CHOPPER APPLICATIONS. Power Electronic Systems. sensors.

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GOOD AFTERNOON !

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  1. GOOD AFTERNOON!

  2. Power electronics converters applications and motors Chethan raj.D 2nd sen M.tech,caid

  3. CONTENTS INTRODUCTION DIFFERENT TYPES OF CONVERTERS UNCONTROLLED RECTIFIERS CONTROLLED RECTIFIERS APPLICATIONS CHOPPER APPLICATIONS

  4. Power Electronic Systems sensors Power Electronics Converters Load • Input • Source • AC • DC • unregulated Output - AC - DC POWER ELECTRONIC CONVERTERS – the heart of power a power electronics system Controller Reference

  5. Power Electronic Systems Why Power Electronics ? sensors Power Electronics Converters • Input • Source • AC • DC • unregulated IDEALLY LOSSLESS ! Output - AC - DC Load Controller Reference

  6. Different types of Power Converters • Diode rectifiers (uncontrolled rectifiers). • Line commutated converters or AC to DC converters (controlled rectifiers). • AC voltage (RMS voltage) controllers (AC to AC converters). Prof. M. Madhusudhan Rao, E&C Dept., MSRIT

  7. Cyclo converters (AC to AC converters at low output frequency). • DC choppers (DC to DC converters). • Inverters (DC to AC converters).

  8. AC to DC Converter Type of input: AC supply (fixed voltage & frequency) Type of output: DC voltage (variable) Prof. M. Madhusudhan Rao, E&C Dept., MSRIT

  9. Diode rectifiers (uncontrolled rectifiers). • the term rectifier describes a diode that is being used to convert AC to DC • Almost all rectifiers comprise a number of diodes in a specific arrangement for more efficiently converting AC to DC than is possible with just a single diode

  10. Full wave rectification • Full-wave rectification converts both polarities of the input waveform to DC, and is more efficient

  11. A full wave rectifier converts the whole of the input waveform to one of constant polarity (positive or negative) at its output by reversing the negative (or positive) portions of the alternating current waveform. The positive (negative) portions thus combine with the reversed negative (positive) portions to produce an entirely positive (negative) voltage/current waveform.

  12. Three-Phase, Full-Bridge Rectifier: Redrawn • Current flows through one diode from the top group and one from the bottom • Diode with highest anode potential from the top and diode with lowest cathode potential from the bottom will conduct

  13. Three-Phase, Full-Bridge Rectifier Waveforms • Six-pulse rectifier: Vd (=VPn-VNn) waveform consists of six segments per cycle • Each diode conducts for 120o • Conduct sequence: 1-2-3…. • Average dc output voltage,

  14. APPLICATIONS Disassembled automobile alternator, showing the six diodes that comprise a full-wave three phase bridge rectifier. A rectifier diode and associated mounting hardware. The heavy threaded stud helps remove heat.

  15. Rectifiers also find a use in detection of amplitude modulated radio signals. - The signal may or may not be amplified before detection but if unamplified a very low voltage drop diode must be used.

  16. Controlled recitifiers

  17. Thyristor Converters • Average dc voltage Vd can be controlled from a positive maximum to a negative minimum on a continuous basis • The converter dc current Id can not change direction • Two-quadrant operation • Rectification mode (power flow is from the ac to the dc side): +Vd & +Id • Inverter mode (power flow is from the dc to the ac side): -Vd & +Id • Inverter mode of operation on a sustained basis is only possible if a source of power, such as batteries, is present on the dc side.

  18. Basic thyristor circuits: Line-frequency voltage source connected to a load resistance • In the positive half cycle of vs, the current is zero until wt=a, at which a gate pulse of a short duration is applied • With the thyristor conducting, vd = vs • vd becomes zero at wt = p • By adjusting the firing angle a, the average dc voltage Vdand current Id can be controlled

  19. Single-Phase Thyristor Converters • One thyristor of the top group and one of the bottom group will conduct • If a continuous gate pulse is applied then this circuit will act like a full bridge diode rectifier and the web forms are as shown below • a=0 for 1 and 2 and a=p for thyristors 3 and 4

  20. 1-Phase Thyristor Converter Waveforms • Assumptions: Ls=0 and purely dc current Id • a: delay angle or firing angle • Prior to wt=0, current is flowing through 3 and 4, and vd = -vs • Beyond wt=0, thyristors 1 and 2 become forward biased, but cannot conduct until a. • vd becomes negative between 0 and a as a consequence of the delay angle • At wt=a, gate pulse applied and current commutation from thyristors 3 and 4 to 1 and 2 is instantaneous (Ls = 0), and vd = vs • Thyristors 1 and 2 will keep conducting until 3 and 4 are fired

  21. Average dc Output Voltage The variation of Vdas a function of a:Average dc voltage is positive until a=90o: this region is called the rectifier mode of operationAverage dc voltage becomes negative beyond a=90o: this region is called the inverter mode of operation

  22. 3-Phase Thyristor Converters • Current Id flows through the one thyristor of the top group and one of the bottom group • If a continuous gate pulse is applied then this circuit will act like a three-phase full bridge diode rectifier and, as a result,

  23. 3-Phase Thyristor Converter Waveforms

  24. Power Electronic Converters in ED Systems DC DRIVES AC-DC + Vo  90o 180o 50Hz 1-phase Average voltage over 10ms 50Hz 3-phase + Vo  90o 180o Average voltage over 3.33 ms

  25. Three Phase Dual Converters • For four quadrant operation in many industrial variable speed dc drives , 3 phase dual converters are used. • Used for applications up to 2 mega watt output power level. • Dual converter consists of two 3 phase full converters which are connected in parallel & in opposite directions across a common load. Prof. M. Madhusudhan Rao, E&C Dept., MSRIT

  26. Four Quadrant Operation Conv. 2 Inverting 2 > 900 Conv. 1 Rectifying 1 < 900 Conv. 2 Rectifying 2 < 900 Conv. 1 Inverting 1 > 900 Prof. M. Madhusudhan Rao, E&C Dept., MSRIT

  27. There are two different modes of operation. • Circulating current free • (non circulating) mode of operation • Circulating current mode of operation

  28. Non Circulating Current Mode Of Operation • In this mode of operation only one converter is switched on at a time • When the converter 1 is switched on, For 1 < 900 the converter 1 operates in the Rectification mode Vdc is positive, Idc is positive and hence the average load power Pdc is positive. • Power flows from ac source to the load

  29. When the converter 1 is on, For 1 > 900 the converter 1 operates in the Inversion mode Vdc is negative, Idc is positive and the average load power Pdc is negative. • Power flows from load circuit to ac source. Prof. M. Madhusudhan Rao, E&C Dept., MSRIT

  30. When the converter 2 is switched on, For 2 < 900 the converter 2 operates in the Rectification mode Vdc is negative, Idc is negative and the average load power Pdc is positive. • The output load voltage & load current reverse when converter 2 is on. • Power flows from ac source to the load Prof. M. Madhusudhan Rao, E&C Dept., MSRIT

  31. When the converter 2 is switched on, For 2 > 900 the converter 2 operates in the Inversion mode Vdc is positive, Idc is negative and the average load power Pdc is negative. • Power flows from load to the ac source. • Energy is supplied from the load circuit to the ac supply. Prof. M. Madhusudhan Rao, E&C Dept., MSRIT

  32. Circulating Current Mode Of Operation • Both the converters are switched on at the same time. • One converter operates in the rectification mode while the other operates in the inversion mode. • Trigger angles 1 & 2 are adjusted such that (1 + 2) = 1800 Prof. M. Madhusudhan Rao, E&C Dept., MSRIT

  33. When 1 < 900, converter 1 operates as a controlled rectifier. 2 is made greater than 900 and converter 2 operates as an Inverter. • Vdc is positive & Idc is positive and Pdc is positive.

  34. When 2 < 900, converter 2 operates as a controlled rectifier. 1 is made greater than 900 and converter 1 operates as an Inverter. • Vdc is negative & Idc is negative and Pdc is positive. Prof. M. Madhusudhan Rao, E&C Dept., MSRIT

  35. Output voltage of a full-wave rectifier with controlled thyristors • Rectifiers are also used to supply polarised voltage for welding. - In such circuits control of the output current is required and this is sometimes achieved by replacing some of the diode in bridge rectifier with thyristors, whose voltage ouput can be regulated by means of phase fired controllers.

  36. Applications • Speed control of DC motor in DC drives. • UPS. • HVDC transmission. • Battery Chargers. Prof. M. Madhusudhan Rao, E&C Dept., MSRIT

  37. BATTERY CHARGERS Microelettrica Power Devices is a leader in the design and development of high reliability substation chargers. • The chargers are configured with main transformer, fully controlled secondary thyristor rectifier, output load resistor and DC filter choke. • Thyristor control is via the industry standard P4500 analogue card, which allows for the firing of of thyristors in inverse parallel or DC bridge configuration with voltage and current feedback.

  38. WONDERSTONE Reverse-polarity water-cooled thyristor controlled rectifier The control system on this rectifier was developed by Microelettrica Power Devices and is the first of its kind in South Africa.

  39. MEGAWATT POWER High Power Heavy Industrial Equipment 16kA/159V water-cooled thyristor controlled rectifier for copper winning Installed at Palaborwa Mining Company

  40. DC Choppers Type of input: Fixed DC supply voltage. Type of output: Variable DC voltage.

  41. DC DRIVES AC-DC-DC DC-DC: Two-quadrant Converter Va T1 D1 + Vdc  ia Q2 Q1 Ia + Va - D2 T2 T1 conducts  va = Vdc

  42. Va Eb DC DRIVES AC-DC-DC DC-DC: Two-quadrant Converter Va T1 D1 + Vdc  ia Q2 Q1 Ia + Va - D2 T2 T1 conducts  va = Vdc D2 conducts  va = 0 Quadrant 1The average voltage is made larger than the back emf

  43. DC DRIVES AC-DC-DC DC-DC: Two-quadrant Converter Va T1 D1 + Vdc  ia Q2 Q1 Ia + Va - D2 T2 D1 conducts  va = Vdc

  44. D1 conducts  va = Vdc Eb Va DC DRIVES AC-DC-DC DC-DC: Two-quadrant Converter Va T1 D1 + Vdc  ia Q2 Q1 Ia + Va - D2 T2 T2 conducts  va = 0 Quadrant 2The average voltage is made smallerr than the back emf, thus forcing the current to flow in the reverse direction

  45. DC DRIVES AC-DC-DC DC-DC: Four-quadrant Converter leg A leg B D3 + Vdc  D1 Q1 Q3 + Va D4 D2 Q4 Q2 Positive current va = Vdc when Q1 and Q2 are ON

  46. DC DRIVES AC-DC-DC DC-DC: Four-quadrant Converter leg A leg B D3 + Vdc  D1 Q1 Q3 + Va D4 D2 Q4 Q2 Positive current va = Vdc when Q1 and Q2 are ON va = -Vdc when D3 and D4 are ON va = 0 when current freewheels through Q and D

  47. DC DRIVES AC-DC-DC DC-DC: Four-quadrant Converter leg A leg B D3 + Vdc  D1 Q1 Q3 + Va D4 D2 Q4 Q2 Positive current Negative current va = Vdc when Q1 and Q2 are ON va = Vdc when D1 and D2 are ON va = -Vdc when D3 and D4 are ON va = -Vdc when Q3 and Q4 are ON va = 0 when current freewheels through Q and D va = 0 when current freewheels through Q and D

  48. References www.scribd.com http://science.howstuffworks.com/maglev-train.htm http://future.wikia.com/wiki/converters

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