09/09/2026
𝗧𝗵𝗲 𝗙𝗮𝗶𝗹𝘂𝗿𝗲 𝗠𝗼𝗱𝗲: 𝗠𝗮𝗴𝗻𝗲𝘁𝗶𝗰 𝗪𝗲𝗱𝗴𝗲 𝗠𝗶𝗴𝗿𝗮𝘁𝗶𝗼𝗻
Magnetic slot wedges (typically composed of ~70% iron filings bonded with resin and fibers) are specified to optimise flux density and reduce slot harmonics. However, under cyclic magnetic forces, core vibration, and thermal expansion, they are prone to mechanical loosening.
Once compromised, the wedges begin to migrate out of the slots. As they break down, they shed iron filings into the winding overhangs and air gap—creating a massive risk of phase-to-phase or phase-to-ground flashover if metallic debris bypasses the ground wall insulation.
𝗧𝗵𝗲 𝗗𝗶𝗹𝗲𝗺𝗺𝗮: 𝗣𝗮𝗿𝘁𝗶𝗮𝗹 𝗥𝗲-𝗪𝗲𝗱𝗴𝗶𝗻𝗴 𝘃𝘀. 𝗙𝘂𝗹𝗹 𝗥𝗲𝘄𝗶𝗻𝗱
While a partial re-wedge might seem like a quick fix on paper, field experience tells a different story.
1. Extraction Complexity: Removing degraded magnetic wedges without scoring the core laminations or nicking the form-wound coil insulation requires delicate, custom tooling.
2. Debris Contamination: Iron filings become embedded between the core packet and wedge. If any metallic particulate remains after cleaning, it will migrate under magnetic stress and breach the insulation barrier over time, leading to catastrophic dielectric breakdown.
3. Fit & Tolerances: Replacing magnetic wedges with non-magnetic alternatives or altered wedge profiles requires custom packing, tight insulation strips, and manual fitting to guarantee slot retention without over-stressing the coils.
In many shops, partial re-wedging carries high failure rates down the line, prompting clients to consider replacing the form-wound coils entirely.
𝗧𝗵𝗲 𝗦𝗼𝗹𝘂𝘁𝗶𝗼𝗻 & 𝗖𝗼𝘀𝘁 𝗔𝘃𝗼𝗶𝗱𝗮𝗻𝗰𝗲
Our engineering team carried out an exhaustive extraction, multi-stage steam cleaning, precision slot prep, and custom re-wedging process.
By executing a full, controlled slot re-wedge and restoring mechanical retention across the slot profile, we eliminated the need for new coils—saving the client well over 73% in capital expenditure and drastically reducing turnaround time.
Is your high-voltage equipment showing signs of wedge migration or slot discharge?
Don't wait for dielectric breakdown. Talk to our high-voltage repair specialists at Mawdsleys BER to evaluate your options for precision re-wedging and coil preservation.
