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6-1 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Chapter 6 Thyristor Converters Thyristor circuits and their control Line-frequency phase-controlled rectifiers and inverters line-frequency ac controlled dc

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6-2 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Thyristor Converters Two-quadrant conversion positive V d implies rectification negative V d implies inverter mode

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6-3 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Primitive circuits with thyristors (1) R load The current is zero until t= The current and voltage v d are in phase Average voltage of load R controlled by adjusting

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6-4 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Primitive circuits with thyristors (2) The current is zero until t= The current lags voltage v d At Instant 2 current becomes zero R L load

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6-5 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Primitive circuits with thyristors (3) L Load with dc voltage

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6-6 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Thyristor Gate Triggering Delay angle is

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6-7 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Full-Bridge Thyristor Converters (1)

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6-8 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters constant dc current load Full-Bridge Thyristor Converters (2)

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6-9 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Thyristor Converter Waveforms (1) Assuming zero ac-side inductance at t=0 thyristors 1,2 are triggered At t= thyristors 3,4 are triggered

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6-10 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Thyristor Converter Waveforms (2)

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6-11 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Thyristor Converter Waveforms (3) The average power in the converter is Average power becomes negative when > 90º ; this is inverter mode of operation

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6-12 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Inverter mode 90º < < 180º average v d is a negative value on dc side average power I d is negative on ac side average power V S RMS I s1 RMS cos 1 is negative

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6-13 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Average DC Output Voltage Assuming zero ac-side inductance

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6-14 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Input Line-Current Waveform input line current i s harmonics

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6-15 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Power, Power Factor Power Power Factor PF

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6-16 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Effect of L s Finite ac-side inductance; constant dc output current

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6-17 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Finite ac-side inductance (1) finite comutation interval u during u all thyristors conduct (v d =0)

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6-18 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Finite ac-side inductance (2)

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6-19 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Input line current i s I s has a trapezoidal waveform DPF is The RMS value of fundamental frequency is

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6-20 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters waveform for =45º average value of v d Practical Thyristor Converter

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6-21 Copyright © 2008 by Jose Bastos Chapter 6 Thyristor Converters Inverter mode with finite AC inductance 90º < < 180º

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