XIX Sympozjum Srodowiskowe PTZE - materialy.pdf

XIX Sympozjum PTZE, Worliny 2009
The second type of the transformer winding forces is the contraction force F c , which acts on
the conductors inside the winding (Fig. 1b). It acts in manner which tends to decrease the
winding height h w (Fig. 2). This force is right-angled on the aforementioned normal force and
causes the consideration worth pressure on the windings. For the design of primary and
secondary windings, the sum of primary contraction force F c1 and secondary contraction force
F c2 is of interest (2):
axis of cilindric winding
Fn
δ ⎛ 1 ⎞
F = F + F = F ⎜2− ⎟
2
h ⎝ k ⎠
a)
c12 c1 c2 n
w
60
( )
where F c12 is the sum of both contraction forces and
δ is the air-gap thickness between the primary and
secondary winding. In the case of different primary
winding height h w1 and secondary winding height
h w2 there exists also a third kind of force, the socalled
shear-strain force F s (Fig. 2).
Fig. 2. Presentation of normal, contraction
and shear-strain force in transformer
Fig. 3. Three-dimensional finite element method model of transformer a) model b) mesh
The transformer must be designed in a manner that prevents eventual damages caused by
forces in short-circuit state. Besides the analytical approach for force calculation also the
numerical approach can be conducted. A 3D finite element model for force determination was
built (Fig. 3a and 3b). In the full paper the comparison between results obtained by the
analytical and the numerical calculation will be presented.
References
Fc2
Fc2
a
Fs
Fc1
Fc1
b δ 2
1 b
Fn
Bσsc hw
[1] I. Zagradišnik, B. Slemnik, Izbrana poglavja iz transformatorjev, University of Maribor, 2007.
b)