Teknologi Elektrik (BBT 3623) Bab 2: Litar Arus Ulang Alik Satu Fasa

Kandungan Nilai Arus ulang alik Litar arus ulang alik rintangan, aruhan dan kapasitan tulin Litar siri RLC Litar kuasa rintangan tulin Litar kuasa aruhan tulin Litar kuasa kapasitan tulin Kuasa dalam litar R-X Vektor Kuasa kompleks dalam litar arus ulang alik Faktor kuasa dalam litar RLC Pembaikan faktor kuasa

2.1 Introduction Electricity is produced by generators at power stations and then distributed by a vast network of transmission lines (called the National Grid system) to industry and for domestic use. It is easier and cheaper to generate alternating current (a.c.) than direct current (d.c.) and a.c. is more conveniently distributed than d.c. since its voltage can be readily altered using transformers. Whenever d.c. is needed in preference to a.c , devices called rectifiers are used for conversion

2.2 How Altenating Current Generated In positions (a), (e) and (i) the conductors, EMF=0  no flux is cut In position (c) maximum flux is cut ,EMF= maximum e.m.f. is induced.

2.2 How Altenating Current Generated In position (g), maximum flux is cut EMF= maximum e.m.f. is induced. (opposite direction) Fleming’s right hand rule

Fleming’s right-hand rule,

2.2 How Altenating Current Generated In positions (b), (d), (f) and (h) some flux is cut and hence some e.m.f. is induced

2.3 Nilai Arus Ulang Alik (saat). V(t)=Voltan seketika (v) Vm=Voltan maksimum (V) (saat).

2.3 Nilai Arus Ulang Alik ISTILAH – ISTILAH VOLTAN AU Vp(Voltan puncak) – merupakan voltan maksimum yang diambil dari rajah gelombang. Bagi gelombang AU voltan puncaknya adalah Vm . Vp-p(Voltan puncak ke puncak) – merupakan nilai yang diambil bermula dari maksimum +ve ke nilai maksimum –ve.

2.3 Nilai Arus Ulang Alik ISTILAH – ISTILAH VOLTAN AU Va(Voltan purata) – merupakan nilai purata bagi gelombang sinus di mana nilainya adalah merupakan nilai purata yang diambil bagi keluasan di bawah garis gelombang AU. Nilainya adalah merupakan 63.7% daripada nilai voltan maksimum.

2.3 Nilai Arus Ulang Alik ISTILAH – ISTILAH VOLTAN AU @ Vpmkd(Voltan punca min kuasa dua) – merupakan nilai yang terpenting di dalam litar elektrik. Kebanyakan meter menunjukkan bacaan di dalam nilai pmkd yang sama dengan 70.7% daripada nilai puncak voltan ulang-alik. @

2.3 Nilai Arus Ulang Alik

2.4 Gambar Rajah Gelombang Au Gelombang Sefasa

2.4 Gambar Rajah Gelombang Au Gelombang Tidak Sefasa D.g.e. teraruh dalam ketiga-tiga gelombang adalah sama (Vm) Tetapi ianya tidak sampai ke nilai maksimum atau nilai sifar secara serentak Gelombang yang melalui titik sifar (0o) diambil sebagai rujukan. perbezaan fasa

2.4 Gambar Rajah Gelombang Au Gelombang Tidak Sefasa Gelombang B sebagai rujukan bagi ketiga-tiganya. Gelombang A mendahului gelombang B dengan α. Gelombang C menyusuli gelombang B dengan β.

2.4 Gambar Rajah Gelombang Au Gelombang Tidak Sefasa

2.4 Gambar Rajah Gelombang Au Gelombang Tidak Sefasa

2.4 Gambar Rajah Gelombang Au Gambar Rajah Vektor / Fasa Gambar Rajah Gelombang Gambar Rajah Vektor / Fasa

2.5 Litar AU - Rintangan Tulin (R)

2.6 Litar AU - Aruhan Tulin (L) (Inductive reactance) f – frekuensi L – aruhan (Hendry) Arus mengekori voltan 90˚ @ (π/2 rad)

2.6 Litar AU - Aruhan Tulin (L)

2.6 Litar AU - Aruhan Tulin (L)

2.6 Litar AU – Kapasitan Tulin (C) (Capacitive reactance) f – frekuensi C – kemuatan (Farad) Arus mendulu voltan 90˚ @ (π/2 rad)

2.6 Litar AU – Kapasitan Tulin (C)

2.6 Litar AU – Kapasitan Tulin (C)

2.6 Litar AU – Kapasitan Tulin (C)

2.7 Litar A.U Siri R-L In any a.c. series circuit the current is common to each component and is thus taken as the reference phasor. Current I lags the applied voltage V by an angle between 0˚ and 90˚ (depending on the values of VR and VL)

2.7 Litar A.U Siri R-L

2.7 Litar A.U Siri R-L

2.7 Litar A.U Siri R-L

2.7 Litar A.U Siri R-L

2.7 Litar A.U Siri R-L

2.7 Litar A.U Siri R-L

2.8 Litar A.U Siri R-C

2.8 Litar A.U Siri R-C Impedance,

2.8 Litar A.U Siri R-C

2.8 Litar A.U Siri R-C

2.9 Litar A.U Siri R-L-C

2.9 Litar A.U Siri R-L-C Impedance,

2.9 Litar A.U Siri R-L-C Impedance,

This effect called series resonance 2.9 Litar A.U Siri R-L-C Z=R This effect called series resonance

2.9 Litar A.U Siri R-L-C

2.9 Litar A.U Siri R-L-C

2.9 Litar A.U Siri R-L-C

2.9 Litar A.U Siri R-L-C Series connected impedances For series-connected impedances the total circuit impedance can be represented as a single L–C–R circuit by combining all values of resistance together, all values of inductance together and all values of capacitance together remembering that for series connected capacitors

2.9 Litar A.U Siri R-L-C

2.9 Litar A.U Siri R-L-C

2.9 Litar A.U Siri R-L-C

2.9 Litar A.U Siri R-L-C

2.9 Litar A.U Siri R-L-C The phasor diagram The phasor sum of V1 and V2 gives the supply voltage V of 100V at a phase angle of 53.13◦ leading. These values may be determined by drawing or by calculation — either by resolving into horizontal and vertical components or by the cosine and sine rules.

2.10 Power In A.C Circuits

2.10 Power In A.C Circuits

2.10 Power In A.C Circuits

2.10 Power In A.C Circuits

2.10 Power In A.C Circuits

2.10 Power In A.C Circuits

2.10 Power In A.C Circuits

2.10 Power In A.C Circuits

2.10 Power In A.C Circuits

2.10 Power In A.C Circuits

2.10 Power In A.C Circuits

2.11 R–L Parallel A.C. Circuit In parallel circuits, the voltage is common to each branch of the network . Thus taken as the reference phasor when drawing phasor diagrams.

2.11 R–L Parallel A.C. Circuit

2.11 R–L Parallel A.C. Circuit

2.11 R–L Parallel A.C. Circuit

2.11 R–L Parallel A.C. Circuit

2.11 R–L Parallel A.C. Circuit

2.12 R–C Parallel A.C. Circuit

2.12 R–C Parallel A.C. Circuit

2.12 R–C Parallel A.C. Circuit

2.12 R–C Parallel A.C. Circuit

2.12 R–C Parallel A.C. Circuit

2.12 R–C Parallel A.C. Circuit

2.12 R–C Parallel A.C. Circuit

2.13 L–C parallel circuit

2.13 L–C parallel circuit Theoretically there are three phasor diagrams possible — each depending on the relative values of IL and IC:

2.13 L–C parallel circuit (i) IL >IC (giving a supply current, I =IL −IC lagging V by 90◦)

2.13 L–C parallel circuit (ii) IC >IL (giving a supply current, I =IC −IL leading V by 90◦)

2.13 L–C parallel circuit (iii) IL =IC (giving a supply current, I =0). condition is not possible in practice due to circuit resistance inevitably being present

2.13 L–C parallel circuit

2.13 L–C parallel circuit

2.13 L–C parallel circuit

2.14 LR–C parallel a.c. circuit the phasor diagram for the LR branch

2.14 LR–C parallel a.c. circuit the phasor diagram for the C branch

2.14 LR–C parallel a.c. circuit the phasor diagram for the circuit

2.14 LR–C parallel a.c. circuit Phasor diagram for I depend on Ic & ILR. There are three possible conditions for this circuit

2.14 LR–C parallel a.c. circuit Condition (i) IC >ILR sin Ø1

2.14 LR–C parallel a.c. circuit Condition (ii) ILR sin Ø1 >IC

2.14 LR–C parallel a.c. circuit Condition (iii) IC=ILR sin Ø1 this is called parallel resonance

2.14 LR–C parallel a.c. circuit 2 Methof of defining supply current I i. Scaled phasor diagram. ii. Polar and complex number method

2.14 LR–C parallel a.c. circuit

2.14 LR–C parallel a.c. circuit

2.15 Power factor improvement For a particular power supplied, a high power factor reduces the current flowing in a supply system, which consequently lowers losses (i.e. I2R losses) cheaper running cost.

2.15 Power factor improvement Industrial loads such as a.c. motors are essentially inductive (R–L) and may have a low power factor. One method of improving (or correcting) the power factor of an inductive load is to connect a static capacitor C in parallel with the load

2.15 Power factor improvement The supply current is reduced from ILR to I, the phasor sum of ILR and IC, and the circuit power factor improves from cos Ø1 to cos Ø2

2.15 Power factor improvement

2.15 Power factor improvement

2.15 Power factor improvement

2.15 Power factor improvement

SEKIAN TERIMA KASIH