M4110 Leakage Reactance Interface User Guide
72A-2243-01 Rev. B 9/04 2-3
September 17, 2004
Failure Modes
When a system short circuit causes high current to flow through a large power
transformer, the windings and internal leads are subjected to extremely high
mechanical forces. The total radial force on a winding can be multiple millions
of pounds and total axial force can be between one and two million pounds.
The extremely high current during the fault conditions is a major source of
mechanical displacements and subsequent transformer failures.
The current flowing in transformer winding conductors sets up an
electromagnetic field in and around the windings, as shown in the simplified
sketches of Figure 2.2 and Figure 2.3. Any current-carrying conductor (I)
which is linked by this field (B) experiences a mechanical force (F) which is
perpendicular to the direction of the current and the field.
In a core form transformer, the forces act radially outward on the outer
winding and radially inward on the inner winding, but because of the radial
fringing at the ends of the windings, there are also axial force components
which tend to compress the windings (Figure 2.2).
Figure 2.2 Generated Forces in a Core Form Transformer
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