Shield segmentation changes the circuits that carry induced current. Identify useful shielding loops and unwanted mounting returns, then compare which path each proposed cut interrupts.
Draw the unsegmented current pattern
Use the source field, plate edges, cuts and mounting contacts to trace current paths within the shield and through supports. The structural-loss review distinguishes eddy currents in metal from circulating currents closed through mechanical connections [1].
A slot changes current continuity. Its direction relative to the current matters more directly than its direction relative to the plate’s longest edge. A slot approximately parallel to one path may interrupt another where the field and current turn.
| Segmentation feature | Path to check | Possible trade-off |
|---|---|---|
| Slot across a shield loop | Induced current providing local shielding | Lower current with increased field penetration |
| Isolated mounting region | Return through tank or bracket | Reduced structural loop but changed support interface |
| Segment boundary | Current crowding near the slot end | New local loss concentration |
| Conductive bridge | Connection across nominally separated pieces | Original loop partly or fully restored |
Preserve the electrical geometry in the model
Represent each segment and its actual contacts. A purely magnetic geometric split may leave electrical continuity unchanged in the numerical model. Conversely, an insulating boundary can remove a connection that exists through a washer or support in the assembly.
Represent conductivity and contact continuity explicitly. A geometrical split without an insulating electrical interface may leave a current path intact; a washer, strap or fastener can bridge a physical slot.
Compare fields and losses together
Evaluate the field reaching the tank, shield resistive loss and loss in connected structural metal before and after segmentation. Keep excitation, material properties and the relevant mounting condition on the same basis. A reduction in shield power alone may simply mean that the shield now carries less useful opposing current.
Inspect slot ends and nearby edges with adequate resolution and realistic geometry. The highest numerical value at an ideal sharp corner can be mesh-sensitive. Check the concentration’s spatial extent and its thermal consequence as well as the point maximum.
Assume a loop has induced voltage 0.10 V RMS, resistance 0.001 Ω and negligible reactance. From I = V/R and P = I²R [2], current is 100 A and heat 10 W. A true open gap removes that path. A mounting strap bridging the gap with an assumed additional 0.001 Ω instead gives 50 A and total loop heat 5 W. The path remains. Check straps, fasteners and tank contacts before accepting segmentation; the resulting local magnetic redistribution and edge losses still require a coupled model.
Verify segments and mounts for unintended bridges. Accept segmentation when it removes the identified unwanted path while the remaining shield meets the defined magnetic and thermal duty.
References
- S. Mikulić and D. Žarko, Stray Losses in Structural Components of Power Transformers, Energies 19, 322, 2026, sections 3.1 and 3.5. DOI: 10.3390/en19020322.
- U.S. Department of Energy, DOE-HDBK-1011/4-92, Electrical Science, Volume 4, 1992.