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Alternating Current Machines

B mn inHong Lam Vocational College

Mn hc: My in xoay chiu

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Alternating Current Machines

Squirrel Cage Rotor

Tng t nh ng c 3 pha

Rotor lng sc

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Alternating Current Machines

Stator ng c 1 pha.

Ging nh phn ng c 3

pha

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Alternating Current Machines

Single-phase Motor Stator

Stator ng c 1 pha.

Nu ch c 1 cun dy ni

vo 1 pha s c t trngxoay chiu nh sau..

Khng to ra c t trng quay.

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Alternating Current Machines

Stator ng c 1 pha.

Phn tnh gm hai cun dyt lch nhau 90 .

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Alternating Current Machines

Stator ng c 1 pha.

Khi c hai cun dy t lch nhau

90 s to ra t trng quay gingnhau.

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Alternating Current Machines

Split-phase Motor/ng c chia pha

to ra s lch pha v dng in chng tadng 2 cun dy c cc c tnh v in khc

nhau v ni chng song song vi nhau.

Mt cun (A) c in tr thp vin cm cao.

Cun cn li (B) c in tr cao vin cm thp

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Alternating Current Machines

ng c chia pha

Hai cun dy b tr lch nhau 90 .

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Alternating Current Machines

Hai cun dy b tr lch nhau 90 .

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Alternating Current Machines

ng c chia pha

Tuy nhin, gia hai cun c gc pha = 30

N lm cho t trng quay yuhn v m men khi ng thp.

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Alternating Current Machines

ng c chia pha

Ngay khi ng c chy, tc ca rotor s giatng theo tc ng ca t trng quay.

Lc ny khng cn s dng hai cun dy na.

Cun (B) c th c ngt ra khi ngun nhvo kha ly tm.

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Alternating Current Machines

ng c chia pha

Hai cun dy c gi l cun CHY- ni lin tc vingun, cun Khi ng- c ngt ra khi ng c tkhong 75% tc nh mc.

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Alternating Current Machines

ng c 1 pha

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Alternating Current Machines

Capacitor Start Motor/ T khi ng C

tng m men khi ng ngi ta s dng 1 t in mcni tip vi cun dy khi ng.

Nhm tng gc pha gia cc cun dy gn ti 90 .

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Alternating Current Machines

th khi mc thm t in.

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Alternating Current Machines

Capacitor Start Motor

M ment khi ng khi thm t.

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Alternating Current Machines

T chyT chy c ni vo cun khi ng gim dng khi

khi ng ng c.

Thng dng cho cc ng c khi ng nhiu ln.

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Alternating Current Machines

ng c dng t chy.

Khi chy theo chiu Thun, cun Al cun chnh (chy), cunBl cun ph (khi ng).

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Alternating Current Machines

ng c dng t chy.

Khi chy theo chiu Ngc, cun Bl cun chnh (chy), cunAl cun ph (khi ng).

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Alternating Current Machines

ng c dng t chy.

ng c kiu ny d dng o chiu quay nhng do hai cun dyging nhau nn hiu qu khi ng khng cao, thng dng chocc ng c cng sut nh.

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Alternating Current Machines

Shaded Pole Motor/ ng c c vng lch pha.

S dng cho cc ng dng cn lc xon nh.

Trong li st thng c mt cun dy sn sinh ra t thng.

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Alternating Current Machines

ng c c vng lch pha.

Phn tnh c x rnh t cc vng ngn mch.Trong cun dy(vng ngn mch) c dng cm ng t cun dyng c.

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Alternating Current Machines

ng c c vng lch pha.

The laminated stator has slots in whichSHORT-CIRCUITED copper Shading Rings are placed.

The inductive shading rings have currents induced

that are LAGGING the coil current.

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Alternating Current Machines

Shaded Pole Motor

A small Squirrel Cage Rotor is between the stator poles.

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Alternating Current Machines

Shaded Pole Motor

The small angle of lag between coil flux and shading ring fluxproduces a weak rotating field effect.

The rotor rotates

TOWARDS

the shading rings.

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Alternating Current Machines

Universal Motor

A Universal motor can operate on either DC or AC

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Alternating Current Machines

Universal Motor

A Universalmotor stator

has field poles

and coils

The rotor is alaminated

armature with

commutator,similar to a DC

Series motor

The stator

core is

laminated for

AC operation

Armature coilsare connected

to the

commutator

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Alternating Current Machines

Universal Motor

Current is passed to the armature via carbon brushesin contact with the commutator

Brushes in

Brush-holders

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Alternating Current Machines

Universal Motor

The Armature and Field Coils are in SERIES

Therefore the field coils and armature carry the SAME current

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Alternating Current Machines

Universal Motor

Characteristics of the Universal Motor:

Starting torque is high

No-Load Speed is high

Torque reduces as speed increases

Speed reduces as load increases

This makes the universal motor suitable for vacuum cleaners,

portable power tools (angle grinders, power drills etc)

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Alternating Current Machines

Reversing Rotation of

Single Phase MotorsReversal of rotation of some

single phase motors is fairly simple

Reversal of rotation of some others is not simple

Reversal of rotation of one type is very difficult

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Alternating Current Machines

Reversing Rotation of

Single Phase MotorsSplit Phase Motor

Reverse

RUN

Winding

Reverse

START

Winding

Reverse

START

Winding

and Switch

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Alternating Current Machines

Reversing Rotation of

Single Phase MotorsUniversal Motor Reverse

Armature

Reversal of ARMATURE is simpler

than reversal of TWO field coils.

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Alternating Current Machines

Reversing Rotation of

Single Phase MotorsShaded Pole Motor

Reversal of Shaded Pole Motor requi res

physical reversal of the stator and shading rings.