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AC to DC Converter (Rectifier)

ASNILELEKTRO FT - UNP

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Penyerahtigafasatak terkendali

Tiga fasasetengah gelombang

Penyearahtigafasasetengahgelombang

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Prosespenyearahan :

Selama polaritas +dari V1 (dari 0-

karena V3 lebih +dari V1 (dari 0-/6), selanjutnya mulai /6-5/6dioda D ON, tetapi karena Vlebih + dari V1 saat 5/6- makaD2 ON, danseterusnya.

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the average value of the output can be found as

t e rmsvaue o t e output vo tage can e oun as

the rmscurrent in each transformer secondary winding can also befound as

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Penyearah gelombang-penuhTigaFasa

Prosespenyearahan : D1, D3, dan D5 akan ON jika anoda terhubung dengan tegangan fasa tertinggi saat itu.

Da, D4, atau D6 akan ON jika katoda terhubung dengan tegangan fasa terendah saat itu.

D1 dan D4, D3 dan D6, D2 dan D5 tidak boleh ON secara bersamaan. Tegangan luaran pada beban dihasilkan dari tegangan line sumber.

Dioda ON secara berpasangan (6,1), (1,2), (2,3), (3,4), (4,5), (5,6), (6,1),. Jadi, dioda ON

dengan urutan 1,2,3,4,5,6,1,

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Tegangankeluaranrata-rata Tegangankeluaranrmsadalah

Aruspuncak yang melalui dioda

Arusrmsyang melalui dioda

Im adalaharuspuncak line sekunder

Vm adalahteganganfasepuncak

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A D ntr ll R tifi

Sin l -PhaseHalf-WaveRectifier

Single thyristor rectifier with resistive load.

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The load average voltage is given by:

Vm

: puncak teganganmasukan

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Gate Signal Generation

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Single thyristor rectifier with: (a) resistive-inductive load; and(b) active load.

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Rectifier for an R - L load.

,

The voltage in the resistance R is as ,

T e oa current s

Rectifier for inductive-active load

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Single-Phase Controlled Rectifier

The load is fed via a thyristor in eachpositive cycle of voltages v1and v2and the load current returns via theneutral N.

With reference in picture bisaides,thyristorT1 can be fired into the ONstate at any time provided that voltagevT1> 0. The firing pulses are delayed

by an angle a with respect to the instantw ere o es wou con uc . n e nexwaveform also illustrates the currentpaths for each conduction state.

until the load current tries to go to anegative value. ThyristorT2 is firedinto the ON state when vT2> 0 whichcorresponds in picture below to the

condition at which v2> 0.

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The load voltage with resistive load is

Tegangan luaran (output) efektif, Vo,rms dan Arus luaran efektif, Io,rms:

+

==

4

2sin

2, mrmsrmso VEV

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AnalisisAnalisisRangkaianRangkaian dengandenganbebanbeban induktifinduktif (RL)(RL)

cos2

,m

DCo

VV =

a pasang yang u ung an parae engan e an ,maka:

( )

cos1, +==m

dcDCo

VEV

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Single-Phase Controlled Rectifier

-(b) half controlled.

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This picture shows the voltage andcurrent waveforms of the fully

resistive load. ThyristorsT1 andT2 must be fired simultaneouslydurin the ositivehalf waveofthe source voltagev

sso as to allow

conduction of current.Alternatively, thyristorsT3 and T4must be fired simultaneouslyduring the negative half wave of

the source voltage. To ensuresimultaneous firing, thyristorsT1and T2 use the same firing signal.

The load voltage is similar to the

vo age o ane w e p asehalf-wave rectifier.

The input current is given by

bridge rectifier with resistive load.

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rectifier with resistive-inductive load

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The high-load inductance generates a perfectly filtered current

and the rectifier behaves like a current source. With continuousload current, thyristorsT1 and T2 remain in the on-state beyondthe positive half-wave of the source voltagevs . For this reason,

.

firing of thyristorsT3 and T4 has two effects:i) they turn off thyristorsT1 and T2; andii) after the commutation they conduct the load current.

This is the main reason why this type of converter is called a .supply current ishas the square waveform for continuousconduction.

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half controlled with high inductive load

Full controlled with R-L Load(high inductive load)

Full wave controlled with R Load

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Three-Phase Half-Wave Rectifier

Three-phase half-wave rectifie

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High Inductive load

If

Resistive load and

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DC current waveforms with resistive load

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AC current waveforms for the half-wave rectifier

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The current waveforms shown above are useful for designing thepower transformer. Starting from

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Then, to establish a relation between ac and dc voltages for

wherea is the secondary to primary turn relation of thetransformer. On the other hand, a relation between the currents is

alsoobtainable.

and

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The meaning of above equation is that the power transformerhas to be oversized 21% at the primary side, and 48% at thesecondar side. Then as ecial transformer hastobebuilt for

this rectifier. In terms of average VA, the transformer needsto be 35% larger that the rating of the dc load. The larger

secondary carries a dc component inside the windings.

Besides, the transformer is oversized because the circulationof current harmonics, which do not generate active power.The core saturation, due to the dc components inside thesecondar windin s also needs to be taken in account for

iron oversizing.

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Three-Phase Half Control Rectifier

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Three-Phase fully Control Rectifier

Three-phase full-wave rectifier

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The load average voltage is given by:

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Latihan

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