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KULIAH 2
1. Sakelar Ideal
Gambar 2.1 Sakelar ideal Kriteria sakelar ideal: Tidak ada rugi-rugi daya saat ON maupun OFF Tidak ada rugi-rugi daya saat peralihan dari ON ke OFF ataupun sebaliknya Untuk OFF ataupun ON hanya membutuhkan daya yang kecil Bi-directional-kah? Rating tegangan dan arus yang memadai untuk aplikasi yang diinginkan Waktu turn ON dan turn-OFF cepat (kecil)
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2. Jenis-jenis Semikonduktor Berdasarkan derajat kemampuan pengendalinya, semikonduktor dibedakan menjadi tiga kelompok (Gambar 2.1) , yakni: dioda, SCR dan controlable switch (misal. BJT, MOSFET/IGBT). (baca: Mohan/ ref. 6)
Gambar 2-2 Jenis semikonduktor Untuk keperluan analisis, setiap devais semikonduktor dianggap berprilaku seperti sakelar ideal. Instantaneous, lossless, and infinite current and voltage handling capability.
breakdown voltage (BV) tinggi ON resistance (Ron) rendah
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waktu switching (tsw) singkat/cepat
Gambar 2.3 Generalisasi kurva I-V semikonduktor
3. Diode
Gambar 2.4Diode.
TEUM
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Prinsip: Devais 2 terminal, Anode (A) dan Katode (K) Dioda ideal akan ON ketika dibias maju dan OFF ketika arus bias maju (iAK) menuju 0A. Catatan: tegangan junction (barrier) saat bias maju (VF) berkisar 0,7V Silikon; 0,3V untuk germanium Aplikasi: Penyearah (rectifier) tidak terkontrol (fixed dc output) Freewheeling
Jenis-jenis dioda Bipolar (p-n junction): dioda pada umumnya, LED Schottky barrier: dioda sckhotty
Recovery Fast (cepat) Slow (lambat)
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Gambar 2.2 Waktu pemulihan dioda Majority carrier devices such as MOSFETS, Schottky diodes have low breakdown voltage in order to have acceptable ON resistance. They have very short switching times. Minority carrier devices such as BJTs, IGBTs, GTOs, SCRs, MCTs have low ON resistance, due to injection of large quantities minority carries into the depletion layer when switched ON. These can have high Breakdown voltage. These are however much slower than majority carrier devices.
Contoh-contoh Dioda: Keluarga 1N200x dengan x : rating arus dioda (x = 1,2,3,4) Membaca Datasheet di kelas!
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4. Thyristor (Silicon Controlled Rectifier -SCR) Aplikasi: Penyearah terkontrol (regulated dc output) Inverter Dimmer/phase controlled Cycloconverter
Karakteristik:
Gambar 2.3 SCR
ON bila gate diberi pulsa trigger (picu) positif saat SCR dibias maju (Anode lebih positif dari katode) OFF seperti halnya diode
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Gate memerlukan daya kecil
Istilah-istilah penting dalam SCR: BV: breakdown voltage (tegangan dadal/tembus) disebut juga breakover BV forward: tegangan breakover saat bias maju (V(BR)), Catatan Desain: Jika sebuah SCR memiliki VBR= 225V, o maka bila terminal anode dan katode SCR mendapatkan tegangan maju sebesar 250 V, maka SCR akan konduksi meski gate tidak dipicu. Ingat!!!: keadaan ini tidak boleh terjadi saat anda mendesain aplikasi o Tetapi apabila tegangan bias maju tersebut masih dibawah VBR, SCR akan tetap dalam kondisi OFF selama gate tidak diberi pulsa trigger positif. Ingat!!!: sebaiknya cek pulsa gate (lebih bagus dengan mengecek tegangan jatuh pada resistor gate kemungkinan sehingga
ada
terjadi
missfiring
baiknya
seorang
(gagal
perancang
membuat pulsa gate berbentuk train pulse.
gagal alternatif
Gambar 2.4 train pulse
picu)
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BV reversed: tegangan breakdown saat bias mundur o Contoh: VBV = 200V Ingat!!!: Jangan
IT : Arus treshold IH : Arus holding (Penahan)
TEUM
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5. Diode vs SCR
Gambar 2.4 Penyearah SCR
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6. Controllable Switch 7. BJT 8. MOSFET 9. IGBT 10. GTO 11. Perbandingan Controllable Switch Materi 6-11 cek di slidenya UNSW. trims
Referensi & Bacaan Lanjutan
(Mohon dibaca!!!)
1.
Aripriharta. (2010). Elektronika Daya Praktis. TEFTUM.
2.
Bose, B.K., (2002).”Modern power electronics and AC drives”. USA, New Jersey: Prentice Hall, Inc.
3.
Emadi, A. et. Al.(2009). “Integrated Power Electronic Converters and Digital Control”.USA, New York: Taylor and Francis Group, LLC
4.
Erickson, R.W. “Fundamentals of Power Electronics”. New York: Kluwer Academic Publishers.
5.
Rashid, M.H. (2001).”Power Electronics Handbook”. Usa: Academic Press.
6.
Mohan (2003).”Power Electronics Converters, Applications, And Design”. John Wiley & Sons, Inc.
7.
Shepherd, W., Zang, L. (2004). “Power Converter Circuits”. New York: Marcel Dekker, Inc.
8.
Williams, B.W.”(2009). Power Electronics Devices, Drivers, Applications, And Passive Components”. University Of Strathclyde, Glasgow.
9.
Shaffer, R. (2007). “Fundamentals of Power Electronics with MATLAB”. USA, Massachusset: Thomson Learning, Inc.
10. F. Rahman. Lecture 1 - Introduction to power electronics (Slide)
