MOTOR INDUKSI

1. MOTOR INDUKSI • Fakultas Teknik Mesin / Industri • Tarumanagara • Edit : • By. Ir. Harlianto Tanudjaja, Mkom,MM

2. Electric Motors • Alternating Current (AC) Motors • Direct Current (DC) Motors • Synchronous • Induction • Separately Excited • Self Excited • Single-Phase • Three-Phase • Series • Compound • Shunt Type of Electric Motors Classification of Motors Motors are categorized on th ebasis of input supply, construction and operation principoles TEXT

3. Type of Electric Motors AC Motors • Electrical current reverses direction • Two parts: stator and rotor • Stator: stationary electrical component • Rotor: rotates the motor shaft • Speed difficult to control • Two types • Synchronous motor • Induction motor

4. Induction Motors

5. Type of Electric Motors AC Motors – Induction motor • Components • Rotor • Squirrel cage: conducting barsin parallel slots • Wound rotor: 3-phase, double-layer, distributed winding • (Automated Buildings) • Stator • Stampings with slots to carry 3-phase windings • Wound for definite number of poles

6. MOTOR INDUKSI TIGA PHASA -. Motorinduksiadalahsuatumesinlistrik yang merubahenergilistrikmenjadienergigerakdenganmenggunakangandenganmedanlistrik dan mempunyai slip antaramedan stator dan medan rotor. -. Motor induksimerupakan motor yang paling banyakkitajumpaidalamindustri.

7. KELEBIHAN MI • Lebih murah dibanding DC Motor • Secara mekanis lebih kuat • Lebih murah biaya pemeliharaan

8. Konstruksi Stator • Dibuatdaripelat-pelattipisdengan slot. • Belitanditempatkanpada slot • Gulungantigafasadilingkarkanuntuksejumlahkutubtertentu • Gulungandiberispasigeometrisebesar 120° antarphasa

9. Bagian-Bagian Motor

10. Introduction • Three-phase induction motors are the most common and frequently encountered machines in industry • simple design, rugged, low-price, easy maintenance • wide range of power ratings: fractional horsepower to 10 MW • run essentially as constant speed from no-load to full load • Its speed depends on the frequency of the power source • not easy to have variable speed control • requires a variable-frequency power-electronic drive for optimal speed control

11. Construction • An induction motor has two main parts • a stationary stator • consisting of a steel frame that supports a hollow, cylindrical core • core, constructed from stacked laminations (why?), having a number of evenly spaced slots, providing the space for the stator winding

12. Construction • a revolving rotor • composed of punched laminations, stacked to create a series of rotor slots, providing space for the rotor winding • one of two types of rotor windings • conventional 3-phase windings made of insulated wire (wound-rotor) » similar to the winding on the stator • aluminum bus bars shorted together at the ends by two aluminum rings, forming a squirrel-cage shaped circuit (squirrel-cage) • Two basic design types depending on the rotor design • squirrel-cage: conducting bars laid into slots and shorted at both ends by shorting rings. • wound-rotor: complete set of three-phase windings exactly as the stator. Usually Y-connected, the ends of the three rotor wires are connected to 3 slip rings on the rotor shaft. In this way, the rotor circuit is accessible.

13. Construction Slip rings Cutaway in a typical wound-rotor IM. Notice the brushes and the slip rings Brushes

14. Komponen Stator • Rangka. • Inti stator • Kumparan/gulungan • Pelatpenutup

15. Inti Stator • Terbuatdarilempeng-lempengbajasilikonberlaminasi. • Untukmemperkecilrugi-rugibesiakibataruspusar

16. Konstruksi Rotor • Fungsi :mengubahdayadari stator menjaditenagamekanik. • Terdapatduatipe, yaitu : • Rotor sangkar • Rotor belitan • Komponen-komponenRotor: • Intibesi rotor, • Kumparan/batangpenghantar, • Cincin • Poros (shaft).

17. Construction Squirrel cage rotor Wound rotor Notice the slip rings

18. Rotor Sangkar • Terdiridaribatangpenghantartebal yang diletakkanpadapetak-petak slot paralel • Keduaujungnyadihubungsingkatdengancincin

19. Rotor Belitan • Konduktor yang digunakanadalahbelitan • Belitanterhubungkecincingeser yang dipasangpada shaft • Belitanterhubungke resistor melaluisikatkarbon

20. PrinsipKerja • Prinsipkerja motor induksimiriptrafo • Rangkaian primer (stator) dansekunder (rotor) tidaksatuinti. • Rangkainsekunderberputar

21. PrinsipKerja • Listrikdipasokkesatorsehinggamenghasilkanmedan magnet yang berputardengankecepatansinkron • Padarangkaian rotor timbularusseginggatimbulkopel • Rotor berputarsearahputaranmedan stator

22. Prinsip Kerja • Bila Kumparan Stator diberi tegangan sumber maka timbul medan putar • Medan putar tersebut akan memotong batang konduktor pada rotor • Kumparan rotor timbul ggl ( E ), sehingga timbul arus ( I ) • Adanya arus dalam medan magnet maka timbul F (ggl) pada rotor • Bila F rotor cukup kuat memikul torka beban, maka rotor akan berputar • Perbedaan kecepatan antara nr dan ns disebut slip yang dinyatakan: • Bila nr = ns maka tidak dihasilkan torka, torka motor akan timbul • apabila nr lebih kecil dari ns

23. Slip • Dalampraktek rotor tidakpernahberputarpadakecepatansinkron • Perbedaankecepatanantaraputaranmedan stator dankecepatan rotor disebut slip • Ns = kecapatan sinkron (rpm) • Nr = kecepatan putaran rotor (rpm)

24. Mode Operasi • +T • Bila ns > nr mesin berfungsi • Sebagai motor. • Plugging • Motor • -1.0 • 1.0 • 0 • S • Generator • Bila ns < nr mesin berfungsi • Sebagai generator. • -T

25. Rotating Magnetic Field • Balanced three phase windings, i.e. mechanically displaced 120 degrees form each other, fed by balanced three phase source • A rotating magnetic field with constant magnitude is produced, rotating with a speed Where fe is the supply frequency and P is the no. of poles and nsync is called the synchronous speed in rpm (revolutions per minute)

26. Synchronous speed

27. Rotating Magnetic Field

28. Rotating Magnetic Field

29. Rotating Magnetic Field

30. Rotating Magnetic Field

31. Rotating Magnetic Field

32. Fb • Fc • FT • t3 • t4 • t5 • t6 • t2 • t0 • t1 • Fa • a • x • ia • ib • ic • -b • -c • x • x • ia • ib • ic • ib • ia • ic • b • c • ia • ib • ic • ia • ic • ib • -a • ic • ia • ib • Fb • Fb • Fc • Fa • FT • FT • FT • FT • Fc • Fa • Fa • Fb • Fc • Fa • Fc • Fc • Fb • Fa • FT • Fb • Prinsip Kerja

33. t3 • t4 • t5 • t6 • t2 • t0 • t1 • a • x • ia • ib • ic • -b • -c • x • x • ia • ib • ic • ib • ia • ic • b • c • FT • ia • ib • ic • ia • ic • ib • -a • Fa • Fc • ic • ia • ib • Fb • Fc • Fa • FT • Fb • FT • Fc • Fa • Fa • Fb • Fc • Fb • Fa • Fc • Fb • FT • Fa • Fb • FT • Fb • Fb • FT • Fc • FT • Fa • a • a • a • a • a • a • x • x • x • x • x • x • -b • -b • -b • -b • -b • -b • -c • -c • -c • -c • -c • -c • x • x • x • x • x • x • x • x • x • x • x • x • Fc • b • b • b • b • b • b • c • c • c • c • c • c • -a • -a • -a • -a • -a • -a • Prinsip Kerja • t0 • t1 • t2 • t4 • t3 • t5

34. Principle of operation • This rotating magnetic field cuts the rotor windings and produces an induced voltage in the rotor windings • Due to the fact that the rotor windings are short circuited, for both squirrel cage and wound-rotor, and induced current flows in the rotor windings • The rotor current produces another magnetic field • A torque is produced as a result of the interaction of those two magnetic fields Where ind is the induced torque and BR and BS are the magnetic flux densities of the rotor and the stator respectively

35. Induction motor speed • At what speed will the IM run? • Can the IM run at the synchronous speed, why? • If rotor runs at the synchronous speed, which is the same speed of the rotating magnetic field, then the rotor will appear stationary to the rotating magnetic field and the rotating magnetic field will not cut the rotor. So, no induced current will flow in the rotor and no rotor magnetic flux will be produced so no torque is generated and the rotor speed will fall below the synchronous speed • When the speed falls, the rotating magnetic field will cut the rotor windings and a torque is produced

36. Induction motor speed • So, the IM will always run at a speed lower than the synchronous speed • The difference between the motor speed and the synchronous speed is called the Slip Where nslip= slip speed nsync= speed of the magnetic field nm = mechanical shaft speed of the motor

37. The Slip Where s is the slip Notice that : if the rotor runs at synchronous speed s = 0 if the rotor is stationary s = 1 Slip may be expressed as a percentage by multiplying the above eq. by 100, notice that the slip is a ratio and doesn’t have units

38. Induction Motors and Transformers • Both IM and transformer works on the principle of induced voltage • Transformer: voltage applied to the primary windings produce an induced voltage in the secondary windings • Induction motor: voltage applied to the stator windings produce an induced voltage in the rotor windings • The difference is that, in the case of the induction motor, the secondary windings can move • Due to the rotation of the rotor (the secondary winding of the IM), the induced voltage in it does not have the same frequency of the stator (the primary) voltage

39. Frequency • The frequency of the voltage induced in the rotor is given by Where fr= the rotor frequency (Hz) P = number of stator poles n = slip speed (rpm)

40. Frequency • What would be the frequency of the rotor’s induced voltage at any speed nm? • When the rotor is blocked (s=1) , the frequency of the induced voltage is equal to the supply frequency • On the other hand, if the rotor runs at synchronous speed (s = 0), the frequency will be zero

41. Sumberteganganbolak-balik yang sinusoid menghasilkanfluks yang sinusoid pula Fluks yang sinusoid inihanyamenghasilkanfluks (medan) pulsasisajadanbebanfluks yang berputarterhadapruang.

42. Tegangan GGL 2. Medan putar stator akan memotong konduktor yang terdapat pada sisi rotor, akibatnya pada kumparan rotor akan timbul tegangan induksi ( ggl ) sebesar • E = tegangan induksi ggl • f = frekkuensi • N = banyak lilitan • Q = fluks

43. Torque • While the input to the induction motor is electrical power, its output is mechanical power and for that we should know some terms and quantities related to mechanical power • Any mechanical load applied to the motor shaft will introduce a Torque on the motor shaft. This torque is related to the motor output power and the rotor speed and

44. Horse power • Another unit used to measure mechanical power is the horse power • It is used to refer to the mechanical output power of the motor • Since we, as an electrical engineers, deal with watts as a unit to measure electrical power, there is a relation between horse power and watts

45. Torka Motor Induksi • R1 • X1 • a2R2/S • a2X2 • I1 • I0 • I’2 • RC • XM • E1 • V1 • Bila Z1 = R1 +jX1 dianggap kecil • maka E1 = V1 , dan T adalah : • Harga S untuk mendapatkan T maks • maka didapat Tmaks pada • dan

46. Kopel Motor Induksi

47. Kurva Torsi dan Slip

48. Daya motor Induksi • Daya masuk Stator : • Daya masuk rotor : • Daya keluar rotor ( P mekanis ) • Rugi-rugi daya : • Sehingga P2 : Pm : Pr = 1 : ( 1 - S ) : S

49. Pengaturan Motor Induksi • Mengubah frekuensi jala-jala dan jumlah kutup : • Bila p ( jumlah kutup ) semakin besar maka • semakin lambat kecepatan putaran dan se • baliknya. • Jumlah kutup dapat diubah2 dengan meren • canakan kumparan stator sedemikian shg • dapat menerima tegangan masuk pada posisi • yang berbeda-beda . • Dari persamaan diatas diketahui bahwa dengan mengubah f semakin besar maka • Menyebabkan kecepatan motor akan semakin besar juga dan sebaliknya.

50. T • V1 • beban • 0.5V1 • n2 • n1 • n • Pengaturan Motor Induksi • Mengatur tegangan jala – jala : • Besarnya kopel motor induksi sebanding • dengan pangkat dua tegangan yang di • berikan ( V1) T = k V2. • Karakteristik beban dapat dilihat seperti • gambar disamping, kecepatan akan be • rubah dari n1 ke n2 untuk tegangan • masuk setengah dari tegangan semula. • Harmonic tinggi dan power factor ren • dah , pengaturan ini biasanya dipakai • untuk peralatan starting torque rendah