AC to DC Converter (Rectifier ) ASNIL ELEKTRO FT - UNP Penyerah - PowerPoint PPT Presentation

AC to DC Converter (Rectifier ) ASNIL ELEKTRO FT - UNP

Penyerah tiga fasa tak terkendali Tiga fasa setengah gelombang Penyearah tiga fasa setengah gelombang

Proses penyearahan : Selama polaritas + dari V 1 (dari 0- π ): dioda D3 lebih dahulu ON π ): dioda D3 lebih dahulu ON karena V 3 lebih + dari V 1 (dari 0- π /6), selanjutnya mulai π /6-5 π /6 dioda D 1 ON, tetapi karena V 2 p 1 2 lebih + dari V 1 saat 5 π /6- π maka D 2 ON, dan seterusnya.

the average value of the output can be found as the rms value of the output voltage can be found as h l f h l b f d the rms current in each transformer secondary winding can also be found as

Penyearah gelombang-penuh Tiga Fasa Proses penyearahan : • D 1 , D 3 , dan D 5 akan ON jika anoda terhubung dengan tegangan fasa tertinggi saat itu. • D a , D 4 , atau D 6 akan ON jika katoda terhubung dengan tegangan fasa terendah saat itu. • D 1 dan D 4 , D 3 dan D 6 , D 2 dan D 5 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, …

Tegangan keluaran rata-rata Tegangan keluaran rms adalah Arus rms pada sekunder trafo Arus rms pada sekunder trafo Arus puncak yang melalui dioda Arus rms yang melalui dioda y g I m adalah arus puncak line sekunder V m adalah tegangan fase puncak

AC – DC controlled Rectifier AC DC controlled Rectifier Single-Phase Half-Wave Rectifier Single Phase Half Wave Rectifier Single thyristor rectifier with resistive load.

The load average voltage is given by: V m : puncak tegangan masukan

Gate Signal Generation

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

Rectifier for an R - L load. When the thyristor is turned ON the voltage across the inductance is When the thyristor is turned ON, the voltage across the inductance is R Rashid, 169 hid 169 The voltage in the resistance R is The load current is h l d i Rectifier for inductive-active load

Single-Phase Controlled Rectifier The load is fed via a thyristor in each positive cycle of voltages v1 and v2 and the load current returns via the neutral N. With reference in picture bisaides, thyristor T1 can be fired into the ON state at any time provided that voltage vT1 > 0. The firing pulses are delayed by an angle a with respect to the instant where diodes would conduct. In be next h di d ld d t I b t waveform also illustrates the current paths for each conduction state. Thyristor T1 remains in the ON state Thyristor T1 remains in the ON state until the load current tries to go to a negative value. Thyristor T2 is fired into the ON state when vT2 > 0, which o e O s e w e v , w c corresponds in picture below to the condition at which v2 > 0.

The load voltage with resistive load is Tegangan luaran (output ) efektif, V o,rms dan Arus luaran efektif, I o,rms : π − α α 1 1 / / 2 2 ⎡ ⎡ ⎤ ⎤ sin 2 + = = ⎢ ⎥ V E V π π o , rms rms m ⎣ ⎦ 2 4

Analisis Analisis Rangkaian Rangkaian dengan dengan beban beban induktif induktif (RL) (RL) 2 V = π α m π cos V o , DC Jika dipasang DIODE KOMUTASI yang dihubungkan paralel dengan beban RL, Jik di DIODE KOMUTASI dih b k l l d b b RL maka: V ( ) = = + α m V E 1 cos π o , DC dc

Single-Phase Controlled Rectifier Single phase bridge rectifier: (a) fully controlled; and Single-phase bridge rectifier: (a) fully controlled; and (b) half controlled.

This picture shows the voltage and current waveforms of the fully controlled bridge rectifier for a controlled bridge rectifier for a resistive load. Thyristors T1 and T2 must be fired simultaneously during the positive half wave of during the positive half wave of the source voltage v s so as to allow conduction of current. Alternatively, thyristors T3 and T4 must be fired simultaneously during the negative half wave of the source voltage. To ensure simultaneous firing, thyristors T1 and T2 use the same firing signal. The load voltage is similar to the voltage obtained with the biphase lt bt i d ith th bi h half-wave rectifier. The input current is given by Waveforms of a fully controlled Waveforms of a fully controlled bridge rectifier with resistive load.

Waveforms of a fully controlled bridge Waveforms of a fully controlled bridge rectifier with resistive-inductive load

The high-load inductance generates a perfectly filtered current and the rectifier behaves like a current source. With continuous load current, thyristors T 1 and T 2 remain in the on-state beyond the positive half-wave of the source voltage v s . For this reason, the load voltage vd can have a negative instantaneous value The the load voltage vd can have a negative instantaneous value. The firing of thyristors T 3 and T 4 has two effects: i) they turn off thyristors T 1 and T 2 ; and ii) after the commutation they conduct the load current. This is the main reason why this type of converter is called a ‘‘naturally commutated’’ or ‘‘line commutated’’ rectifier The naturally commutated or line commutated rectifier. The supply current i s has the square waveform for continuous conduction.

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

Three-Phase Half-Wave Rectifier Three-phase half-wave rectifie

High Inductive load Resistive load and es st ve oad a d If

the load average voltage is the load average voltage is

DC current waveforms with resistive load

AC current waveforms for the half-wave rectifier

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

Then, to establish a relation between ac and dc voltages for where a is the secondary to primary turn relation of the transformer. On the other hand, a relation between the currents is also obtainable. and

The meaning of above equation is that the power transformer has to be oversized 21% at the primary side, and 48% at the secondary side. Then, a special transformer has to be built for secondary side. Then, a special transformer has to be built for this rectifier. In terms of average VA, the transformer needs to be 35% larger that the rating of the dc load. The larger rating of the secondary respect to primary is because the rating of the secondary respect to primary is because the secondary carries a dc component inside the windings. Besides, the transformer is oversized because the circulation of current harmonics, which do not generate active power. The core saturation, due to the dc components inside the secondary windings, also needs to be taken in account for y g , iron oversizing.

Three-Phase Half Control Rectifier

Three-Phase fully Control Rectifier Three-phase full-wave rectifier

The load average voltage is given by:

Latihan

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