Arus Listrik AC 1 Fasa
Pertemuan 4 : Teknik Tenaga Listrik
CONTENT
1. Generation of alternating voltage and current 2. Different forms of E.M.F equations.
3. A.C through R, L and C and power factor
4. A.C through R,R-C and R-L series and parallel circuits
5. Active and reactive components of circuit & Active, reactive and apparent power.
What is A.C?
An alternating current (a.c) is the current which changes periodically both in magnitude and direction.
Different A.C. waveforms
Cycle
One complete set of positive and negative values of alternating quantity is known as cycle.
Time Period
The time taken by an alternating quantity to complete one cycle is called its time period T.
Frequency
The number of cycles/second is called the frequency of the alternating quantity. Its unit is hertz(Hz)
f = 𝑃𝑁 120
f = PN/120 where f is frequency of electric supply, P is number of poles in the motor and N = speed in rpm.
Also
f = 1
𝑇 or T = 1
𝑓
Amplitude
The maximum value, positive or negative, of an alternating quantity is known as its amplitude.
Generation of alternating voltage and current
The machine which are used to generate electrical voltages are called generators. The generators which generate purely sinusoidal a.c.
voltages are called ALTERNATORS.
Generation of alternating voltage and current
Basic principle of an alternator is the principle of electromagnetic induction. The sine wave is generated according to FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION.
Faraday’s Law of Electromagnetic Induction
Hukum Faraday 1 :
Setiap perubahan medan magnet pada kumparan akan menyebabkan gaya gerak listrik (GGL) yang diinduksi oleh kumparan tersebut.
Hukum Faraday 2 :
Setiap perubahan medan magnet pada kumparan akan menyebabkan gaya gerak listrik (GGL) Induksi yang sebanding dengan laju perubahan fluks.
Let us see how an alternator produces a sine wave, with the help of simplest form of an alternator called single turn or single loop alternator.
Different forms of E.M.F equations
The standard form of an alternating voltage is given by,
Different forms of E.M.F equations
R.M.S Value
Nilai RMS adalah jumlah daya AC yang menghasilkan efek pemanasan yang sama dengan daya DC yang setara. Nilai RMS adalah akar kuadrat dari nilai rata-rata (mean) dari fungsi kuadrat dari nilai instan. Simbol yang digunakan untuk mendefinisikan nilai RMS adalah VRMS atau IRMS. Nilai RMS, HANYA mengacu pada tegangan sinusoidal yang bervariasi waktu, arus atau bentuk gelombang yang kompleks adalah besarnya perubahan bentuk gelombang dari waktu ke waktu dan tidak digunakan dalam analisis atau perhitungan rangkaian DC karena besarnya selalu konstan.
R.M.S Value
Average Value
Form Factor (K
f)
Peak Factor (K
P)
Phase
The phase of an alternating quantity at any instant is the angle Ф (in radians or degrees) travelled by the phasor representing that alternating quantity upto the instant of consideration, measured from the reference.
Phase
Phase Difference (In Phase)
Phase Difference (Lag)
Phase Difference (Lead)
Phasor Diagram
In phase
Kuis 1 TTL minggu 5
1. Hitunglah daya yang diserap oleh beban R = 600 Ohm, yang dihubungkan dengan V = 40 sin 314 t Volt!
2. Nyatakan dalam bentuk fasor berikut dalam bentuk polar,
rectangular, dan Eksponensial, serta gambarkan diagram phasor nya.
Apparent Power (S)
It is defined as the product of r.m.s value of voltage (V) and current (I). It is denoted by S.
It is measured in unit volt-amp (VA) or kilo volt-amp (kVA).
Real or True Power (P)
It is defined as the product of applied voltage and active component of the current. It is real component of the apparent power.
It is measured in unit watts (W) or kilo watts (kW).
Reactive Power (Q)
It is defined as product of the applied voltage and the reactive component of the current. It is represented by Q.
It is measured in unit Volt-Amp Reactive (VAR) or kilo Volt-Amp Reactive (kVAR)
Segitiga Daya
Power Factor
It is defined as factor by which the apparent power must be multiplied in order to obtain the true power.
It is the ratio of true power to apparent power.
Power Factor
It is also defined as the ratio of resistance to the impedance.
KEYPOINT: Nature of power factor is always determined by position of current with respect to the voltage.
Power Factor
If current lags voltage power factor is said to be lagging. If current leads voltage power factor is said to be leading.
A.C through R
Current
Phasor Diagram
Power
A.C through L
Current
Phasor Diagram
Power
A.C through C
Current
Phasor Diagram
Power
AC through RL series circuit
Impedance
Power
AC through RC series circuit
Power
Latihan Soal 1
Sebuah resistor dan inductor
dihubungkan secara seri seperti gambar di samping. Tentukan :
(a) Arus yang mengalir, (b) Sudeut fasa
(c) VR dan VL
(d) Sketsa Diagram Phasor nya (e) Daya yang dihasilkan
Latihan Soal 2
Sebuah resistor dan kapasitor
dihubungkan secara seri seperti gambar di samping. Tentukan :
(a) Arus yang mengalir, (b) Sudut fasa
(c) VR dan VC
(d) Gambarkan Diagram Phasor nya (e) Daya yang dihasilkan
Latihan Soal 3
Sebuah resistor, inductor dan kapasitor dihubungkan secara seri seperti gambar di samping. Tentukan :
(a) Arus yang mengalir, (b) Sudut fasa
(c) V pada coil dan V pada C
(d) Gambarkan Diagram Phasor nya (e) Daya yang dihasilkan
Latihan Soal 4
Sebuah rangkaian R-C yang terdiri dari C = 4.7 µ F yang dihubungkan seri dengan R = 300 Ohm, Terhubung dengan supply 220 V, 50 Hz.
Tentukan (a) Arus
(b) Power Factor
(c) Daya Aktif, Semu, dan Daya Rekatif.
