Transformer %Z
Transformer %Z
3% impedance is the leakage impedance and magnetising impedance is separate.
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RE: Transformer %Z
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If we learn from our mistakes I'm getting a great education!
RE: Transformer %Z
Thanks,
Daniel
RE: Transformer %Z
RE: Transformer %Z
If V1 is the primary voltage , Zp=Rp+j*Xp primary winding impedance [j=i=sqrt(-1)] , Xp it is the reactance of magnetic field losses of primary winding and Rp is the primary winding resistance, E1 is mmf [ magnetomotive force ] of primary winding, I1 is the primary current [ all parameter as complex number] then:
V1=I1*Zp+E1
The same remarks for secondary winding:
E2=I2*Zs+V2
E1/E2=w1/w1=kw where w1,w2 is number of turns of primary respective secondary windings.
If we'll multiply the second equation by kw we'll get:
E1=I'2*Z's+V'2 and substituting E1 in the first equation we'll get:
V1=I1*Zs+I'2*Z's+V'2
Then we can draw the following scheme:
From this we can state:
I1=Io+I'2
Io=E1/j*Xm +E1/Rfe [ Io=I1 when I'2=0]. Where Xm=effective magnetic field reactance and Rfe = magnetic core
active losses equivalent resistance. Io=E1 (Xm -j*Rfe)/(Rfe*Xm)=E1*Const
Usually Io=2-3%*Irated if V1=primary rated voltage. As |Zp*I1rated| is less than 5%of V1rated E1>0.95*V1rated.
Vsc=short-circuit voltage for I1=I1rated [V'2=0]
in order to find Vsc the secondary is short-circuited and the I1=Irated.
Vsc=Zp*I1rated+E1sc Zp*I1rated is still approx.5% then E1sc=0-5%*V1rated.
As Io=E1*Const for full V1 is only 3% for E1sc will be [directly proportional] 3%*5%=1.5/1000*I1rated.That means may
be neglected. I1=Io+I'2 if Io~0 then I1=I'2 and Vsc=(Zp+Z's)*I1rated so Zsc=Vsc/Irated=Zp+Z's.