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Module 2.

Control techniques

a) One Quadrant b) Two Quadrant c) Four Quadrant.

Figure shows the technique of controlled conversion from AC to DC. When the

switch is turned on it conducts curerent in the direction of the arrow. the output wave form

depends on switch control waveform and pulse triggered switch, such as SCR, GTO, MCT or

level triggered switch like BJT, MOSFET, IGBT. Usually the source has an inductance but for

analysis we neglect this inductance.

In fig a, the circuit is arranged as to get the output voltage and currents remains in

the same positive direction, and hence the circuit operates in only one quadrant or first

quadrant converter. it includes one SCR and one diode and circuit will operate as rectifier.

In fig b, the circuit contains one SCR and is arranged such as to get the output

voltage in positive and negative directions but current remains in the positive direction,

and hence the circuit operates in two quadrant converter. In first quadrant circuit will

work as rectifier and in forth quadrant it will work as inverter.

In fig c, the circuit contains two SCRs as converter1 and converter2 and are

arranged such as to get the output voltage and current in both the directions, and hence the

circuit operates in all four quadrant. In first quadrant converter1 acts as rectifier, in second

quadrant converter2 acts as inverter, in third quadrant converter2 acts as rectifier, and in

fourth quadrant converter1 acts as inverter.

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Single-phase half wave controlled rectifier with resistive load.

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Single-phase half wave controlled rectifier with inductive load.

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Single-phase half wave controlled rectifier with inductive load with effect of

freewheeling diode.

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Single-phase half wave controlled rectifier with resistive load.

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Single-phase full wave controlled rectifier with inductive load.

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Single-phase half wave controlled rectifier with inductive load with

freewheeling effect

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DC to DC converters (CHOPPER)

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Classification of Choppers

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