TAJUK KEMAHIRAN DAN TAHAP

ELEKTRONIK INDUSTRI – TAHAP 2 (SEMESTER 2)

No. DAN TAJUK MODUL M06 ELECTRIC MACHINE

No. DAN TAJUK PENGALAMAN PEMBELAJARAN

LE1 MAINTAIN DC MOTORLE2 MAINTAIN AC MOTORLE3 CHECK FUNCTION OF SERVO MOTOR

OBJEKTIF PRESTASI AKHIRAN / TERMINAL PERFORMANCE OBJECTIVE

MAINTAIN AC/DC MOTOR AND CHECK OPERATING CONDITION OF SERVO SYSTEM USING SPECIFIED EQUIPMENT AND HAND TOOLS SO THAT OPERATING CONDITION AS PER SPECIFICATION.

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INSTITUT LATIHAN JABATAN TENAGA MANUSIAKEMENTERIAN SUMBER MANUSIA

MALAYSIA

KERTAS PENERANGAN

(B05-02-06-LE1-IS1a)

ISI KANDUNGAN

LE1 – MAINTAIN DC MOTOR

TASK 05.05 – Maintain DC Motor

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No. & TAJUKPENGALAMAN PEMBELAJARAN

LE1 Maintain DC Motor

No. & TAJUK TUGASAN

TASK 05.05 – Maintain DC Motor

Code No. : B05-02-06-LE1-IS1a Muka : 1 drp. 8

TAJUK : KEELEKTROMAGNETAN

TUJUAN : Kertas penerangan ini menerangkan tentang asas kemagnetan , sifat-sifat urat daya magnet, system medan magnet dan kawalan bagi motor DC.

PENERANGAN :

FUNDAMENTALS OF MAGNETISM

The operating processes in electrical machines are based on the elemental physical principles of

i. Electromagnetic induction and ii. Lorentz force

i. Electromagnetic induction

To understand how generators work, knowledge of the law of induction is critical. Induction

a. A voltage is induced when a conductor is moved through a magnetic field of the force F.

b. The induced voltage evokes a current in the conductor if this is located in a closed circuit.

It is electromagnetic induction which produces voltage and current in generators regardless of whether the generator is a three-phase or a DC generator

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Code No. : B05-02-06-LE1-IS1a Muka : 2 drp. 8

The effect of magnetic fields

To grasp how electrical machines work, it is important to understand not only the law of induction but how the magnetic field acts on a current-carrying conductor:

ii. Lorentz Force

a. When a current-carrying conductor passes through an external magnetic field, a force is exerted perpendicular to the direction of the current flow and to the magnetic field

b. This force is proportional to the current I flowing through the conductor and to the magnetic induction B of the external magnetic field. 

c. This so-called Lorenz force is responsible for the motion induced in a current-carrying conductor in a magnetic field. It is the basis for how every motor operates.

Right hand rule

A simple method of determining the direction of the Lorenz force is the so-called "right-hand rule". The variables

a. Velocity v of electrons (opposite direction to current flow) b. Magnetic induction B of external magnetic field c. Force F (Lorenz force)

are all located at right angles to each other. If you know the directions of two variables, the direction of the third variable is automatically given by the"right-hand rule".

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Code No. : B05-02-06-LE1-IS1a Muka : 3 drp. 8

SIFAT-SIFAT URAT DAYA MAGNET

Dia antara sifat-sifat urat daya ialah :-

a. Mempunyai kekutuban Utara dan Selatan

b. Urat daya bergerak dari Utara ke Selatan

c. Urat daya tidak memotong diantara satu dengan yang lain.d. Kekuatan urat daya magnet bergantng kepada ketelapan teras.

SISTEM MEDAN MAGNET

Sistem ini terdiri daripada elektromagnet atau magnet kekal bagi motor berukuran kecil sama ada dengan satu atau lebih pasang kutub. Kutub ini dipasang pada kuk ( yoke).

Tugas kutub ini ialah untuk menghasilkan medan magnet yang akan bertindak balas dengan medan dari angker.

Kutub antara mungkin diperlukan bagi motor berukuran sederhana dan besar. Kutub ini bersaiz kecil dan dipasang diantar kutub utama. Kutub antara dalam penjana dipasang

sama kekutubanyan dngan kutub utama mengikut arah pusingan angker. Manakala motor, kutub ini ini dipasang berlainan dengan kutub utama.

a) Penjana b) Motor

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Code No. : B05-02-06-LE1-IS1a Muka : 4 drp. 8

Kutub antara bertugas sebagai pencegah bunga api di penukar tertib dan membaiki tindak balas angker.

Belitan kutub antara ini disambung secara siri dengan angker. Angker ialah bahagian yang berputar dalam mesin DC.

Ia terbina daripada lapisan-lapisan kepingan besi yang dilekapkan menjadi bentuk silinder yanng berlubang alur pada jarak yang sama. Gegelung pengalir angker akan dipasangkan kedalam lubang alur itu.

Bagi penjana bekalan elektrik hanya diperlukan oleh medan tetapi bagi motor bekalan elektrik dibekalkan kepada angker dan medan.

Penukar tertib diperbuat daripada bar kuprum yang ditebat diantaar satu sama lain oleh mika. Gegelung angker disambungkan ke penukar tertib ini dan seterusnya disambung keluar melalui

sentuhan berus karbon yang terletak diatas permukaan penukar tertib. Bagi motor, penukar tertib bertugas sebagai penetap arah arus yang mengalir dalam pengalir

dibawah tindakan sesuatu kutub magnet. Walaupun kedudukan pengalir itu berubah, arah pengaliran arus akan tetap sama dan ini penting bagi memperolehi daya tolakan yanng berterusan untuk memutarkan angker dalam satu arah.

PRINSIP ASAS MESIN ELEKTRIK

A conductor loop whose axis is rotatable is located within the magnetic field of a permanent magnet.

A direct current flows through the conductor loop in the direction shown by the arrows

Due to the Lorenz force there are forces being exerted on the upper and lower conductor rod which

are precisely perpendicular to the magnetic field and to the conductor rod.

These forces constitute a torque that is exerted on the rotor resulting in the conductor loop's rotation

around the illustrated axis.

After a rotation of 90 degrees (with respect to the illustrated starting position) a stable state is

reached and the conductor loop comes to a standstill.

If you now reverse the direction of the current flow, another torque arises due to the Lorenz force

which causes another rotation

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Code No. : B05-02-06-LE1-IS1a Muka : 5 drp. 8

GERAKAN PUTARAN MOTOR

i) Medan Magnet di dalam Motor AT

ii) Arus dalam Motor AT

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Code No. : B05-02-06-LE1-IS1a Muka : 5 drp. 8

iii) Daya di dalam Motor AT

iv) Tork dalam Motor AT

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Code No. : B05-02-06-LE1-IS1a Muka : 7 drp. 8

v) Operasi Motor AT

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Code No. : B05-02-06-LE1-IS1a Muka : 8 drp. 8

SOALAN :

1. Berikan 2 prinsip elemen fizikal bagi keelektromagnetan.

2. Nyatakan sifat-sifat urat daya

2. Terangkan 5 prinsip gerakan putaran motor AT.

RUJUKAN:1. “Electrical And Electronics Engineering Studies”. Kementerian Pendidikan Malaysia; 2006;.

Dewan Bahasa dan Pustaka .2. The current course "Electrical Machines 1: Commutator Machines", Copyright © 2002-2002

LUCAS-NÜLLE GmbH.

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