Electrotehnica si masini electrice (power point 4/4)

Motorul asincron trifazat

Universitatea Tehnica din Cluj-Napoca, Facultatea de Mecanica 1/34

Elemente constructive

http://www.indezine.com/powerpoint/backgrounds/088.html



Camp magnetic invartitor

Phase a Phase b Phase c

BbBa

Bc

Br Ba

BbBc

Br

Ba

Bb

Bc

Br

Ω1 = ω/p [rad/s]n1 = 60 Ω1/2π [rot/min]n1 = 60·(2πf/p)/(2π ) = 60·f/p




Principiul de functionare

n1

n<n1

n1 N

S

n<n1

N

S

n1-n

Alunecare : s = (n1 – n)/n1

f2 = sf1

v

B

F

FM




Bilantul puterilor

PCu1PFe1

PCu2PFe2

Pm

P2P1

P = MΩ1 =P1 – (PCu1 + PFe1)

P PM

PM = MΩ = P2 + Pm + PFe2

P2 = MrΩ

P1 = √3UlIlcosφ =(PCu1 + PFe1)+ (PCu2 + PFe2 + Pm) + P2

η = P2/ P1 = MrΩ/(√3UlIlcosφ)




Caracteristica mecanica naturala

M = 2Mk/(s/sk + sk/s)

M

s1sksn

Mk

MN

Mp

0

sN = (n1 – nN)/n1

MN = PN/ΩN

MN = PN/(2πnN/60)

s = 0 → n = n1 = 60·f/p

Mk = λ·MN

sk = sN[λ + √(λ2 – 1)]

s = 1 → n = 0Mp = 2Mk/(1/sk + sk/1)




Caracteristica mecanica naturalan

MMkMN

nN

n1

nk

0 Mp

MN = PN/ΩN

MN = PN/(2πnN/60)

n1 = 60·f/p

Mk = λ·MN

sk = (n1 – nk)/n1

nk = n1(1 - sk)

Mp = 2Mk/(1/sk + sk)

Mr




Caracteristici mecanice artificiale

n1 = ct. nk = ct. M = M(U2)

U ≠ UN, U < UNn

MMk

n1

UNnk

0 Mr

U3 < U2 < U1 < UN

U1U2U3

Mk2 Mk1Mk3

Mk1/Mk2 = (U1/U2)2

Mk2 = Mk1(U2/U1)2

U1 = UN = 400 V, U2 = 300 V

Mk2 = Mk1(U2/U1)2 = 0.56·Mk1





f ≠ fN, f < fN, f > fN

Mk1/Mk2 = (f2/f1)2

Mk2 = Mk1(f1/f2)2

f1 = fN = 50 Hz, f2 = 70 Hz

Mk2 = Mk1(f1/f2)2 = 0.51·Mk1

n

Mk

n1

fNnk

0

n1 = n1(f), sk = sk(1/f) M = M(1/f2)

Mk2

f2

Mk1

f1

Mk3

f3

Mk4

f4

Mr

f2 < f1 < fN < f3 < f4




Pornirea

A. Pornirea directan

MMkMN

nN

n1

nk

0 Mp

Md = M – Mr = J·dΩ/dt

M = Mr →Md = 0dΩ/dt = 0→ Ω = ct.

I

ttp

Imax

IN

0

Imax = (8…10)IN




Pornirea

B. Pornirea “Y – Δ”Conexiune

“Y”

Conexiune“Δ”

Conectarea bornelor

230 V

400 V

n

MMk

n1

nk

0 Mpy MpΔMr




=

Pornirea

B. Pornirea “Y – Δ”

Conexiune“Y”

Conexiune“Δ”

Conectarea bornelor

230 V

400 V

Z

ZZ

Z Z

Z

IlY

IlΔ

IlY = IfY = 230/Z

IlΔ = √3 IfΔ = √3 ·400/Z

IlY/IlΔ= 1/3

IlY = (1/3)IlΔ

MPY/MPΔ = (230/400)2 = 1/3

MPY = (1/3)MPΔ




=

Pornirea

C. Pornirea progresiva (soft-starter)n

MMk

n1

UN

nk

0

Up

Mp

M = M(U2)

Mr




=

Modificarea turatiei

A. Modificarea nr. perechi de poli “p”

s = (n1 – n)/n1

n1 = 60·f/p [rot/min]

n = n1(1 – s) n = (1 – s)·60f/p

s = 0.05, f = 50 Hz, p = 1 → n = 2850 rot/mins = 0.05, f = 50 Hz, p = 2 → n = 1425 rot/min

Motorul Dahlander




=


B. Modificarea frecventei

n = (1 – s)·60f/p

1. f < fN (n < nN)

U/f = ct. → Mk = ct.

n

Mk

n1

fN

0 M

f2

f1

f2 < f1 < fN

MNMr

Mlim = ?

Mk = ct. (λ = ct.)Mlim = MN




=


B. Modificarea frecventei

2. f > fN (n > nN)

P = Mr·Ω → Plim = PN

n

Mk

n1

fN

0 M

f2

f1

f2 < f1 < fN

MNMr

f5 > f4 > f3 > fN

f3 f4

f5

Mlim = PN/Ω

U/f = ct. ? U = UN = ct. Mk = Mk(1/f2) → λ <<U/f = ct. ?

Ωlim = PN/Mr




=

Franarea

A. Franarea dinamica

n

Mk

fN

0 MMrMf1

I1

Mf2

I2

I1 > I2




=

Franarea

B. Franarea in contracurent

Rf

Rf

n

Mk0

M

n1

-n1

Mr

Rf

Rf = 0

Mf1 Mf2


Motorul de curent continuu


=





=


M




=

Principiul de functionare

NSB

F

B

F

M

M = kEΦEIA

ΦE = BAP

E = kEΦEΩ

NSBv

Ω




=

Ecuatia de functionare

UA = RAIA+E

MIA

UA

IE

UE

IA

UA

ERA

RE

UE

IE

UE = REIE




Caracteristica mecanica naturala

UA = RAIA+EE = KEΦEΩIA = M/kEΦE

Ω = UA/kEΦE – [RA/(kEΦE)2]M

Ω

0 M

Ω0

Ω0 = UA/kEΦE

MN

ΩN

ΩN = 2πnN/60

MN = PN/ΩN

UA = UAN

ΦE = ΦEN





Ω = UA/kEΦEN – [RA/(kEΦEN)2]M

Ω

0 M

Ω0

Mr

UN

U1

U2

U3

U3 < U2 < U1 < UN A. UA < UAN

MIA

UA

IEN

UEN





Ω = UAN/kEΦE – [RA/(kEΦE)2]M

B. ΦE < ΦEN (IE < IEN)

MIA

UAN

IE

UE

Ω

0 M

Ω0

Mr

ΦEN

ΦE2 < ΦE1 < ΦEN

ΦE1

ΦE2





Ω = UAN/kEΦEN – [(RA+RAS)/(kEΦE)2]M

C. RAS > 0

M IA

UAN

IEN

UEN

RAS

Ω

0 M

Ω0

RAS3

RAS3 > RAS2 > RAS1

RAS2

RAS1

RAS= 0

Mr




Pornirea

Ω = 0 → E = 0 → IAP = UAN/RA

A. Pornirea directa

MIA

UAN

IEN

UEN

Ω

0 M

Ω0

MP

MP = kEΦEIAP

Mr




Pornirea

Ω

0 M

Ω0

Mpmin

(IAPmin)

RAS1

RAS= 0

Mr

Mpmax

(IAPmax)

RAS1+RAS2

IAPmax = UAN/(RA+RAS1+RAS2)

B. Pornirea reostatica

M

UAN

IEN

UEN

RAS1

RAS2

MPmax = kEΦEIAPmax

MPmin = kEΦEIAPmin



Pornirea

IAP = UAP/RA

C. Pornirea progresiva

MIA

UAP→UAN

IEN

UEN

Ω

0 M

Ω0

Mr

UN

UA↑

MP

UAP

MP = kEΦEIAP




A. UA < UAN → Ω < ΩN

MIA

UA↓

IEN

UEN

Ω = UA/kEΦE – [RA/(kEΦE)2]MΩ

0 M

Ω0

Mr

UN

UA↓

MN

Mlim = ? Mlim = MN (IAlim = IAN)




B. ΦE < ΦEN → Ω > ΩN

(IE < IEN)

MIA

UAN

IE↓

UE↓

Mlim = ?

Ω

0 M

Ω0

Mr

ΦEN

UA↓

ΦE↓

MN

Plim = PN → Mlim = PN/Ω Ωlim = PN/Mr



Franarea

A. Franarea in contracurent

MIAf

-UAN

IEN

UEN

Rf

-UAN = -(RA + Rf)IAf + kEΦENΩIAf = (UAN+kEΦENΩ)/(RA+Rf)

Ω

Mr0 M

Ω0

-Ω0

Mf

Ω = -UAN/kEΦEN + [(RA+Rf)/(kEΦEN)2]M

Mf = kEΦENIAf

Mf0



Franarea

B. Franarea dinamica

Ω

Mr0 M

Ω0

Mf

Mf = kEΦENIAf

MIAf

IEN

UEN

Rf

0 = (RA + Rf)IAf + kEΦENΩIAf = - kEΦENΩ/(RA+Rf)

Ω = - [(RA+Rf)/(kEΦEN)2]M

Electrotehnica si masini electrice (power point 4/4)

Documents

Transcript of Electrotehnica si masini electrice (power point 4/4)