PENGANTAR Motor Induksi

04/04/2009 1

PENGANTAR

Motor Induksi

Oleh

Mesin Listrik

„

Transformator

„

Mesin Arus Bolak-balik

„

Mesin Arus Searah

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Mesin Arus Bolak-balik

„ Mesin Sinkron ‹ Motor Sinkron ‹ Generator Sinkron „ Mesin Asinkron ‹ Motor Asinkron ‹ Generator Asinkron

Jumlah fasa

„ Mesin tiga fasa

‹ Motor Induksi

‹ Motor kondensor sinkron ‹ Generator Sinkron

„ Mesin satu fasa

‹ Motor Split-phase ‹ Motor Capasitor ‹ Motor Shaded-pole ‹ Motor Universal

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Mesin Listrik yang lain

„ Mesin DC ‹ Motor DC  Penguat terpisah  Penguat sendiri • Serie • Shunt

• Compound (long, short, differentiative, commulative)

‹ Generator DC

„ Spesial Motor

‹ Stepper motor

‹ Linier stepper motor

Jenis Konstruksi Rotor dan

Kutub

„ Jenis Rotor Sangkar

(squerell-cage rotor)

„ Jenis Rotor Lilit ( wound rotor)

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Keuntungan Motor AC

„

Konstruksi kuat

„

Effisiensi tinggi

„

Biaya pemeliharaan murah

„

Starting mudah

„

Effisiensi tinggi pada

Kerugian Motor AC

„

Kontrol Putaran Susah

„

Torsi start kecil

„

Putaran akan turun bila

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Konstruksi Mesin AC

„ Bagian Stator : Inti dan Lilitan stator

„ Bagian Rotor : Inti dan Lilitan rotor

‹ Rotor sangkar (sqeurell-cage rotor) ‹ Rotor Lilit (wound rotor)

Konstruksi MI

Some motor frames are sized so that just the surface area is suitable

Some motor frames are sized so

Some motor frames are sized so

that just the surface area is suitable

that just the surface area is suitable

Blowers may be added to motors to allow operation at low speed including “0” RPM with 100% Torque continuous

Blowers may be added to

Blowers may be added to

motors to allow operation at

motors to allow operation at

low speed including

low speed including ““00”” RPM RPM with 100% Torque continuous

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Types of AC Motors

Definite purpose “laminated frame” designs provide higher power

densities & improved torque to inertia performance.

Definite purpose

Definite purpose ““laminated framelaminated frame”” designs provide higher power

designs provide higher power

densities & improved torque to

densities & improved torque to

inertia performance.

inertia performance.

T-Frame Construction Motors allow commonality in footprint & shaft height.

T

T--Frame Construction Motors allow Frame Construction Motors allow commonality in footprint & shaft

commonality in footprint & shaft

height.

height.

Match Motor type to meet your needs!

Bagian motor Induksi

Motor Frame

Motor Frame

Assembly

Assembly

Rotor & Shaft

Rotor & Shaft

Stator Winding

Stator Winding

Assembly

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Persamaan yang digunakan

„ Hukum Ampere „ Hukum Farady Hukum Kirchoff

∫

H.dl

=

∑

NI

dt

Nd φ

e

=

∑

I

= 0

∑

IZ

=V

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Medan Putar

„ Medan putar terjadi pada sumber tiga fasa yang diberikan

Prinsip Kerja motor induksi

3fasa

„ Kumparan stator diberi tegangan 3 fasa akan

timbul medan putar dengan kecepatan :

N_s = 120f / p

„ Medan putar akan memotong konduktor pada

rotor, sehingga akan menimbulkan tegangan induksi pada lilitan rotor sebesar

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„ Karena lilitan rotor merupakan lilitan yang tertutup, maka akan

ada arus yang mengalir pada rotor

„ Adanya arus dalam medan magnet, akan timbul gaya F pada

rotor

„ Gaya dikalikan dengan jari-jari koduktor rotor akan

menghasilkan kopel (torsi)

„ Jika torsi yang dihasilkan lebih besar dibandingkan dengan

torsi beban, maka rotor akan berputar sesuai dengan arah medan putar

„ Agar tagangan E_2s tetap ada, maka diperlukan perbedaan

„ Perbedaan antara ns dengan nr dinyatakan dengan persamaan slip (s)

• S = {(n_s – n_r)/n_s} 100%

„ Kemungkinan

 s = 0 Kondisi motor diam

( ) ( ) ( ) ( )2 2 2 2 2 2 2 2 2 2 2 SX R SE X R E I s s + = + = ( ) ( )2 2 2 2 2 2 / S X R E I + = Atau

04/04/2009 23 ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − + = S S R R S R₂ / _{2 2} 1 Karena Maka ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − S S R₂ 1

s I 0 I I1 1 R X1 s I m I 1 R s I 1 X

04/04/2009 25 V1 R’2 X’2 ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − S S R'2 1 R1 X1 m JX s I I_R m I > > v

2 2 2 2 2 2 1 2 ) ( ) / ( ' X a S R a E I + = 2 2 2 2 2 2 2 2 ) ( ) / ( / cos X a S R a S R a impedansi tahanan + = = ϕ ϕ ω ω 3 E₁I '2 cos P T = = ( )

(

)

(

)

2 2 2 2 2 2 2 2 2 2 1 3 X a S R a R Sa V T + = _ω

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Diagram daya

„ Daya input

„ Daya output stator (daya input rotor)

„ Daya output rotor (daya mekanis)

„ Daya output (daya yang digunakan)

φ Cos VI P_in = 3

s

R

I

P

₂

=

3

₂

'

2

'

⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − = s s R I P_m 3 ₂ ' ₂ ' 1 m N dalam P_out −

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Input power P_sup

Stator Copper loss 3 I_sta2 R_sta

Rotor Copper loss 3 I_rot2 R_rot Stator Iron loss

3 V_sta2 _{/ R} c Ventilation and friction losses Output power P_out Air gap powerP_ag Developed power P_dv = 3 I_rot2 R_rot (1-s)/s Air gap

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Karakteristik Torsi-Slip

„ Gambar 4 2 2 2 2 2 2 2

'

'

'

3

X

s

R

sR

V

T

+

=

ω

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„ Starting Torque

„ Pull-up Torque

„ Break down Torque

Pengaturan Putaran Motor

Induksi

„ Tegangan Input „ Frekuensi input „ Tahanan Rotor „ Jumlah kutub

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METODA STARTING

„ Pada rotor belit :

digunakan tahanan mula yang besarnya dipilih sedemikian sehingga torsi start = torsimax. Setelah motor berputar, dalam keadaan nominal rotor dihubung singkat.

„ Pada rotor sangkar :

a. Untuk daya kecil dapat distart langsung b. Start dengan auto trafo

Machine design Speed sensorless Machine Theory Non-linear control Real-time control DSP application Utility interface Renewable energy

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Klasifikasi Motor Induksi

berdasar temperatur

„ Motor Induksi Klas A ()

„ Motor Induksi Klas B (80oC) „ Motor Induksi Klas C ()

„ Motor Induksi Klas D ()

„ Motor Induksi Klas E (40oC) „ Motor Induksi Klas F (75o C)

Berdasar operasi

„ Drip-proof motor

„ Splash-proof motor

„ Totally enclose. Non-ventilated

„ Totally enclose, fan-cooled motor

Name plate motor

„ Jenis Motor dan jumlah fasa „ Tegangan nominal „ Arus nominal „ Frekuensi kerja „ Power factor „ Jenis isolasi Temperatur operasi

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Pengaman Motor Induksi

„ Thermal Overload

„ Over current/ over load

„ Under/over voltage „ Under frequency „ Pole slip „ Out of excitation „ Over flux „ Negative sequence „ De-rating Factor „ Earth Foult

Pemilihan dan Penggunaan

Motor Induksi

„ Standar dan klasifikasi motor

„ Klasifikasi pendinginan

‹ Drip-proof, splash-proof, totally enclose, totally

enclose fan-cooled, Explosion-proof,

„ Klasifikasi sesuai dengan sifat listrik dan mekanis ;

‹ Standart, Torsi start tinggi, slip tinggi.

„ Ukuran motor dalam HP

„ Pemilihan putaran, pengereman,

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INTRODUCTION TO ELECTRIC DRIVES - MODULE 1

Torque and speed profile

10 25 45 60 t (ms)

speed (rad/s)

100

The system is described by: T_e – T_load = J(dω/dt) + Bω

J = 0.01 kg-m2, B = 0.01 Nm/rads-1 and T_load = 5 Nm.

What is the torque profile (torque needed to be produced) ? Speed profile

INTRODUCTION TO ELECTRIC DRIVES - MODULE 1

Torque and speed profile

10 25 45 60 t (ms) speed (rad/s) 100 0 < t <10 ms Te = 0.01(0) + 0.01(0) + 5 Nm = 5 Nm 10ms < t <25 ms Te = 0.01(100/0.015) +0.01(-66.67 + 6666.67t) + 5 = (71 + 66.67t) Nm 25ms < t< 45ms Te = 0.01(0) + 0.01(100) + 5 = 6 Nm l e B T dt d J T = ω + ω +

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INTRODUCTION TO ELECTRIC DRIVES - MODULE 1

Torque and speed profile

10 25 45 60 speed (rad/s) 100 10 25 45 ₆₀ Torque (Nm) 72.67 71.67 -60.67 -61.67 56 t (ms) t (ms) Speed profile torque profile

INTRODUCTION TO ELECTRIC DRIVES - MODULE 1

Torque and speed profile

10 25 45 ₆₀ Torque (Nm) 70 -65 6 t (ms)

For the same system and with the motor torque profile given above, what would be the speed profile?

J = 0.001 kg-m2, B = 0.1 Nm/rads-1 and T_load= 5 Nm.

Electric Drives 55

Example 1.3. gear - box drive torque / time curve

Let us consider an electric drive for an elevator with the data shown in figure 1.11.

Figure 1.11. Elevator electric drive with multiple mechanical transmissions and counterweight