ayam belanda

lantai habuk kayu

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ayam ni suka bertelur kat semak. kalau bagi mkn, time tu x de maka dia tengah mengeramlh tu. kene lah pergi cari kat mana bersembunyi.Click ads for your tq or like.

2.1 AC Motors

1. Synchronous motor

 

A synchronous motor is distinguished by its rotor spinning at the same rate as the oscillating field which drives it. Another way of saying this is that it has zero slip under usual operating conditions. Contrast this with an induction motor, which must slip in order to produce torque.  Sometimes a synchronous motor is used, not to drive a load, but to improve the power factor on the local grid it's connected to. It does this by providing reactive power to, or consuming reactive power from the grid. In this case the synchronous motor is called a Synchronous condenser.

A synchronous motor may have either a revolving armature or a revolving field, although most synchronous motors are of the revolving-field type. The stationary armature is attached to the stator frame, while the field magnets are attached to a frame that revolves with the shaft.  The field coils are excited by direct currents, either from a small DC generator (usually mounted on the same shaft as the motor and called an exciter), or from some other source. Fig. 1 shows a directly connected exciter.

Electrical power plants almost always use synchronous generators because it's very important to keep the frequency constant at which the generator is connected. Low power applications include positioning machines, where high precision is required, and robot actuators.

Advantages

Synchronous motors have the following advantages over non-synchronous motors:

     i.      Speed is independent of the load, provided an adequate field current is applied.

   ii.      Accurate control in speed and position using open loop controls, eg. stepper motors.

 iii.      They will hold their position when a DC current is applied to both the stator and the rotor windings.

 iv.      Their power factor can be adjusted to unity by using a proper field current relative to the load.

   v.      Their construction allows for increased electrical efficiency when a low speed is required (as in ball mills and similar apparatus).

2. Squirrel-Cage Motor

            The most common form of induction motor is the squirrel-cage type. This motor has derived its name from the fact that the rotor, or secondary, resembles the wheel of a squirrel cage. Its universal use lies in its mechanical simplicity, its ruggedness, and the fact that it can be manufactured with characteristics to suit most indus­trial requirements.  Squirrel-cage motor consists essentially of two units, namely stator and rotor.  The stator (or primary) consists of a laminated sheet-steel core with slots in which the insulated coils are placed. The coils are so grouped and connected as to form a definite polar area and to produce a rotating magnetic field when connected to a polyphase alternating- current circuit.

            The rotor (or secondary) is also constructed of steel laminations, but the windings consist of conductor bars placed approximately parallel to the shaft and close to the rotor surface. These windings are short-circuited, or connected at each end of the rotor, by a solid ring. The rotors of large motors have bars and rings of copper connected at each end by a conducting end ring made of copper or brass. The joints between the bars and end rings are usually elec­trically welded into one unit, with blowers mounted on each end of the rotor. In small squirrel-cage rotors, the bars, end rings, and blowers are of aluminium cast in one piece instead of welded together.

            The air gap between the rotor and stator must be very small in order for the best power factor to be obtained. The shaft must, therefore, be very rigid and be furnished with the highest grade of bearings, usually of the sleeve or ball-bearing type. A cutaway view of a typical squirrel-cage induction motor is shown in Figure 2.

Advantages:

     i.      Because of its simplicity of construction and because it can be built with electrical characteristics to suit almost any industrial requirement, has made it one of the most widely used machines.

   ii.      The speed of a squirrel-cage motor is nearly constant under normal load and voltage conditions.

 iii.      Suitable for medium or low-starting-torque requirements.

Disadvantages:

Squirrel-cage motors as a rule are not suitable where a high starting torque is required.

3.  Wound – Rotor Motor

 

A wound rotor motor is a variation of the in­duction motor but does not use a squirrel cage winding. The stator of the wound rotor motor is the same as the standard three-phase induction motor, in that it produces a three-phase rotating magnetic field. The rotor is not a squirrel cage winding.  Squirrel cage windings have cast conducting bars shorted together end rings and installed in the laminated The rotor of the wound rotor motor act consists of conductors (magnet wire) wound into coils on the rotor. (See Figure 3.)

                                                                                                      

The stator in the wound-rotor motor is identical to the stator in the squirrel-cage motor. The basic difference in the two motors lies in the rotor winding.  In the squirrel-cage motor, the rotor winding is nearly always self-contained; it is not connected either mechanically or electrically to the outside power-supply or control circuit. However, in wound-rotor motors, the rotor winding consists of insulated coils of wire that are not permanently short-circuited, but are connected in regular succession to form a definite polar area having the same number of poles as the stator. The ends of these rotor windings are brought out to collector rings, or slip rings.

The wound-rotor motor is often used in cranes, hoists, and elevators. These devices are operated intermittently and for short periods of time, where exact speed regulation and loss in efficiency are of little consequence.  Wound-rotor motors can be used to start extremely heavy loads. Hence, they are suitable for: (1) driving various types of machinery that require development of considerable starting torque to overcome friction; (2) accelerating extremely heavy loads that have a flywheel effect or inertia; and !3) overcoming back pressures set up by fluids and gases, as in reciprocating pumps and compressors.

Advantages:

     i.      The wound rotor motor has higher starting torque per line amps than do most AC squirrel cage motors.

   ii.      The wound-rotor motor can operate at any speed from its maximum full-load speed down to almost standstill.

 iii.      Wound-rotor motors have the ability to start extremely heavy loads. Hence they are suitable for:

Ø  Driving various types of machinery that require development of considerable starting torque to overcome friction.

Ø  Accelerating extremely heavy loads that have a flywheel effect or inertia.

Ø  Overcoming back pressures set up by fluids and gases in the case of reciprocating pumps and compressors.

Disadvantages:

     i.      Most motor starters used with wound rotor motors have a provision that will not allow you to start the motor if all secondary resistance is shorted out of the secondary.

   ii.      The wound rotor motor is a higher maintenance motor because of the windings that are fitted into the rotor.

 iii.      If lowered speed is required over longer periods, poor speed regulation and loss in efficiency may become prohibitive.

4.  Split-phase induction motor

            Another common single-phase AC motor is the split-phase induction motor, commonly used in major appliances such as washing machines and clothes dryers. Compared to the shaded pole motor, these motors can generally provide much greater starting torque by using a special startup winding in conjunction with a centrifugal switch.

            In the split-phase motor, the startup winding is designed with a higher resistance than the running winding. This creates an LR circuit which slightly shifts the phase of the current in the startup winding. When the motor is starting, the startup winding is connected to the power source via a set of spring-loaded contacts pressed upon by the not-yet-rotating centrifugal switch. The starting winding is wound with fewer turns of smaller wire than the main winding, so it has a lower inductance (L) and higher resistance (R). The lower L/R ratio creates a small phase shift, not more than about 30 degrees, between the flux due to the main winding and the flux of the starting winding. The starting direction of rotation may be reversed simply by exchanging the connections of the startup winding relative to the running winding.

            The phase of the magnetic field in this startup winding is shifted from the phase of the mains power, allowing the creation of a moving magnetic field which starts the motor. Once the motor reaches near design operating speed, the centrifugal switch activates, opening the contacts and disconnecting the startup winding from the power source. The motor then operates solely on the running winding. The starting winding must be disconnected since it would increase the losses in the motor.

5.  Repulsion motor

            Repulsion motors are wound-rotor single-phase AC motors that are similar to universal motors. In a repulsion motor, the armature brushes are shorted together rather than connected in series with the field. Several types of repulsion motors have been manufactured, but the repulsion-start induction-run (RS-IR) motor has been used most frequently. The RS-IR motor has a centrifugal switch that shorts all segments of the commutator so that the motor operates as an induction motor once it has been accelerated to full speed. RS-IR motors have been used to provide high starting torque per ampere under conditions of cold operating temperatures and poor source voltage regulation. Few repulsion motors of any type are sold as of 2005.

6.  Shaded-pole motor

            A common single-phase motor is the shaded-pole motor, which is used in devices requiring low starting torque, such as electric fans or other small household appliances. In this motor, small single-turn copper "shading coils" create the moving magnetic field. Part of each pole is encircled by a copper coil or strap; the induced current in the strap opposes the change of flux through the coil (Lenz's Law), so that the maximum field intensity moves across the pole face on each cycle, thus producing a low level rotating magnetic field which is large enough to turn both the rotor and its attached load. As the rotor accelerates the torque builds up to its full level as the principal (rotationally stationary) magnetic field is rotating relative to the rotating rotor. Such motors are difficult to reverse without significant internal alterations.

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SURFACE WIRING AND PVC CONDUIT CIRCUIT

Objectives  :

• Wiring and accessories installation of lamp controller circuit using 2 way switch and photocell.
• Wiring and accessories installation of socket ring circuit and air cond circuit.

Accessories :

• 1.5 mm² & 2.5 mm² Single & Double PVC Cable
• 4 mm² Single PVC Cable
• Distrubution Board – MCB, ELCB dan Main Switch (isolator) & Copper Bar
• Pendafour Lamp
• Photocell             
• 1 Way Switch
• 2 Way Switch
• 3 pin 13 A Socket (x4)
• 15A Socket Outlet
• DOL Starter
• 40mm” high impact PVC conduit
• Batton Holder, End-Box, inspection tee, insection elbow, intersection 4 way, intersection 3 way, saddler bar, cilling rose. 
• Cut-out Fuse, Neutral Link & kwH base.   
• Wire Connector
• Aluminium/Plumbum clip

Tools :

• Test Pen
• Screw Driver & Philip Screw Driver
• Measuring Tape
• Cutter
• Combination plier & side cutting plier
• Wire cutter
• Hacksaw
• Cable Puller
• Measuring ruler
• Chalk
• Conduit Bender
• Warrington hammer
• Cordless
• Jack clip cutter
• Aluminium Clip, Nail &Skrew
• Multimeter

Wiring steps :

• Students given brief explanations regarding wiring work by instructor.
• Students were asked to understand the circuit, diagram and orders that given by the instructor.
• Tools and materials that required for the wiring is identified.
• Then tools and materials that required for the wiring is prepared.
• After that, wiring baton is installed.
• Followed by cable installation. The surface wiring should be done neatly, well arranged and straight.
• Next, cables’ end point fitted with connector and circuit accessories are installed.
• Lastly, the circuit are tested.

Material used :-

Cable :-

Required cable length as shown in table below:- 

 

The sizes of cable are depended on load and current flow of the circuit.   

Wiring Circuit Diagram

Actual Wiring Circuit

 

TOOLS & EQUIPMENTS

Discussion

1.         In surface wiring there are two main circuits. They are:-

a)      Cut-out unit circuit – mainly supervised and under maintenance by Tenaga Nasional Berhad (TNB).

b)      Consumer End-Circuit – in-house circuit and owned by consumer. 

2.                  Cut-out circuit is supplied with 240V which is sufficient for the household usage. 415V single phase and neutral that tapped into cut-out circuit yields 240V 50Hz (single phase).

3.                  In surface wiring, neat, well arranged and straight wiring is essential because it is open air wiring and can be seen by bare eye. Due to open-air wiring, double PVC cable is used for safety.

4.                  Y or Star connection is used for domestic wiring ( house & premise with low electric usage).

5.                  Implementation of Polarization Test is to ensure 3 regulations below are obeyed. They are :-

a)                  Single phase switch, fuse and protection device are connected to phase cable only

b)                  Middle touch for Edison lamp holder and BS60238 standard screw types in circuit with earth cable have outer touch space or screw connected to neutral cable.

c)                  All the wiring connected to the dedicated socket outlet and accessories.

 

KESIMPULAN

Amali ini dijalankan adalah untuk mengenalpasti bahagian-bahagian utama di dalam kerja pendawaian 3 fasa iaitu isolator, pemutus litar arus baki, pemutus litar jenis kenit dan litar akhir.

Penggunaan warna yang berbeza pada setiap dawai adalah bagi memudahkan seseorang wireman dapat membuat pendawaian dengan tepat dan cepat untuk mengelakan sebarang kesilapan yang memungkinkan letupan ataupun kematian.

Alatan utama yang diperlukan untuk amali ini ialah pemutar skru kepala rata dan Philips, pena ujian, kotak alatan, playar gabung, pemotong sisi, playar muncung panjang, dan gerudi tanpa kord sebagai alat Bantu bagi mempercepatkan lagi kerja pendawaian dapat dijalankan.

Kerosakan biasa yang berlaku pada komponen, contohnya pada pemutus litar arus baki (ELCB) adalah disebabkan kesilapan penyambungan dawai-dawai pada bahan.

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INDUSTRY AND VTE

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no blacklist

aku dpt panggilan ni. aku ingat orang ppd yg call, rupanya orang ni. puas aku layan 22:24 minit. x payah kau cari, bila aku nak nanti aku cari.

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burung hantu p2

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nasib baik x boleh mkn, kalau x dah lama aku sembelih. dah, pergi main jauh2.
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burung hantu

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sapa suruh kau x simpan jaring, kan dah kene burung hantu. kuku tajam pulak tu. mcm mana nak tanggalkn? guna sarung tangan. x dpt bukak, dah terbelit. terpaksa gunting jaring. taruk dlm sangkar dulu la, bg adik2 tgk. uttttttt utttttttt.

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lambang zionis di laptop/pc anda. mesti delete.

PERHATIAN KAWAN2!!!

buka komputer/laptop anda
pda "Local Disk (c) ,
THEN "Program Files"
THEN "Microsoft Office"
THEN "Media"
THEN "CAGCAT10"'
cari gambar no "J0285926" dan klik.
Anda akn jmpa gambar Lambang/
Bendera ZIONIS,ISRAEL.lngkap (sama dngan wrna aslinya) dngan lilin (sarana ibadah
mereka).
DELETE pic itu!!

Utk pngtahuan anda ,
gmbar trsbut ada di sluruh PC dan LAPTOP.
Sbarkan kpd smua saudara islam!! CARI smpai
JUMPA!!

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DINAMOMETER

 merupakan item yang paling penting dalam sel ujian dan digunakan untuk mengukur output kuasa enjin.

Prestasi enjin

·         Prestasi enjin bergantung kepada beberapa faktor iaitu:

i)                    Kelajuan omboh yang digunakan di dalam enjin

ii)                  Jenis bahan pelincir

iii)                Keadaan suhu semasa enjin bekerja

iv)                Isipadu nisbah campuran bahan api dan udara yang masuk ke dalam ruang pembakaran.

·         Nisbah campuran ini penting kerana kekuatan letupan yang berlaku semasa lejang kuasa bergantung padanya.

 

Istilah Kendalian Enjin

Takat Terakhir Atas (TTA) : aras yang paling tinggi sekali yang mana bahagian atas omboh boleh sampai di dalam silinder.

Takat Terakhir Bawah (TTB) : aras yang paling bawah sekali yang mana bahagian atas omboh boleh sampai.

Gerek : Garis pusat silinder sebelah dalam.

Lejang : Jarak pergerakan omboh di antara TTA dan TTB.

Jarak Tayang : Jarak diantara pusat aci engkol dengan pusat cemat engkol.

                        2 jarak tayang = 1 jarak lejang.

Pusingan seminit (PSM / RPM) : Jumlah pusingan aci engkol dalam satu minit.

Kitar : Dereten lejang yang lengkap.

Istilah Kemuatan Enjin

Isipadu Anjakan

Isipadu di dalam silinder dalam cm padu yang di anjak oleh omboh bergerak dari TTA ke TTB.

 

Isipadu Kelegaan

Isipadu silinder apabila omboh berada di TTA / isipadu ruang pembakaran.

 

Jumlah Isipadu

Isipadu silinder apabila omboh berada di TTA / isipadu ruang pembakaran + isipadu kelegaan.

 

Nisbah Mampatan

Jumlah isipadu campuran bahan api yang dimampat oleh omboh dari TTB ke TTA ketika lejang mampatan.

 

Ujian Dinamometer

-          Ujian ini dilakukan untuk mengukur keluaran kuasa enjin.

-          Peralatan Ujian :

a)      Blower           

-          Digerakkan 1 inci dari paras lantai untuk mengelakkan ia bergerak semasa beroperasi.

-          Digunakan untuk menyejukkan enjin kereta dan enjin dinamometer tester.

b)      Mesin Dinamometer

c)      Komputer

d)     Stripe Kabel

-          dipasang secara menyilang pada bahagian hadapan kereta.

-          Untuk mengelakkan kereta bergerak ke kanan dan kekiri semasa pengujian dan boleh tayar kereta rosak.

e)      RPM counter

-          tetapkan start speed 60 km/h

-          tetapkan RPM counter pada nilai 6000 / 6500

f)       Temperature Sensor Detector

-          buka bonet hadapan.

-          Cabut keluar penyukat minayak pelincir dan gantikan dengan temperature sensor detector.

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Fiber

Or fibre is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread. Fibers are of great importance in the biology of both plants and animals, for holding tissues together. Human uses for fibers are diverse. They can be spun into filaments, thread, string or rope. They can be used as a component of composite materials. They can also be matted into sheets to make products such as paper or felt. Fibers are often used in the manufacture of other materials.

Fibers used by man come from a wide variety of sources.

• Natural fibers include those produced by plants, animals, and geological processes. They can be classified according to their origin:
• Vegetable fibers are generally based on arrangements of cellulose, often with lignin: examples include cotton, linen, hemp jute, flax, ramie, and sisal. Plant fibers serve in the manufacture of paper and cloth.
• wood fiber, distinguished from vegetable fiber, is from tree sources. Forms include ground wood, thermo mechanical pulp (TMP) and bleached or unbleached kraft or sulfite pulps. Kraft and sulfite, also called sulphite, refer to the type of pulping process used to remove the lignin bonding the original wood structure, thus freeing the fibers.
• Animal fibers consist largely of particular proteins. Instances are spider silk, sinew, catgut and hair (including wool). Polar bear fibers are noted for being hollow.

• Mineral fibers comprise asbestos. Asbestos is the only naturally occurring long mineral fiber. Short, fiber-like minerals include wollastinite, attapulgite and halloysite.

• Man-made fibers may come from natural raw materials or from synthetic chemicals.
• Many types of fiber are manufactured from natural cellulose, including rayon, modal, and the more recently developed Lyocell. Cellulose-based fibers are of two types, regenerated or pure cellulose such as from the cupro-ammonium process and modified or derivitized cellulose such as the cellulose acetates. Fiberglass made from specific glass formulas and optical fiber, made from purified natural quartz, are also man-made fibers that come from natural raw materials. Metallic fibers can be drawn from ductile metals such as copper, gold or silver and extruded or deposited from more brittle ones such as nickel, aluminum or iron.

   Synthetic fibers are a subset of man-made fibers, which are based on synthetic chemicals (often from petrochemical sources) rather than arising from natural materials by a purely physical process. Such fibers are made from polyamide nylon, PET or PBT polyester, phenol-formaldehyde (PF),polyvinyl alcohol fiber (PVOH), polyvinyl chloride fiber (PVC), polyolefins (PP and PE), or acrylic polymers, although pure polyacrylonitrile PAN fibers are used to make carbon fiber by roasting them in a low oxygen environment. Traditional acrylic fiber is used more often as a synthetic replacement for wool. Carbon fibers and PF fibers are noted as two resin-based fibers that are not thermoplastic, most others can be melted. Aromatic nylons such as Kevlar and Nomex thermally degrade at high temperatures and do not melt. More exotic fibers have strong bonding between polymer chains (e.g. aramids), or extremely long chains (e.g. Dyneema or Spectra). Elastomers can even be used, e.g. spandex although urethane fibers are starting to replace spandex technology.

Coextruded fibers have two distinct polymers forming the fiber, usually as a core-sheath or side-by-side. Coated fibers exist such as nickel-coated to provide static elimination, silver-coated to provide anti-bacterial properties and aluminum-coated to provide radar chaff. Radar chaff is actually a spool of continuous glass tow that has been aluminum coated. An aircraft-mounted high speed cutter chops it up as it spews from a moving aircraft to foil radar signals.

Micro fibers in textiles refer to sub-denier fiber (such as polyester drawn to 0.5 dn). Denier and Detex are two measurements of fiber yield based on weight and length. If the fiber density is known you also have a fiber diameter, otherwise it is simpler to measure diameters in micro metres. Microfibers in technical fibers refer to ultrafine fibers (glass or meltblown thermoplastics)often used in filtration. Newer fiber designs include extruding fiber that splits into multiple finer fibers. Most synthetic fibers are round in cross-section, but special designs can be hollow, oval, star-shaped or trilobal. The latter design provides more optically reflective properties. Synthetic textile fibers are often crimped to provide bulk in a woven, non woven or knitted stucture. Fiber surfaces can also be dull or bright. Dull surfaces reflect more light while bright tends to transmit light and make the fiber more transparent.

Very short and/or irregular fibers have been called fibrils. Natural cellulose, such as cotton or bleached kraft show smaller fibrils jutting out and away from the main fiber structure.

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