09/09/2026
๐ง๐ต๐ฒ ๐๐ฎ๐ถ๐น๐๐ฟ๐ฒ ๐ ๐ผ๐ฑ๐ฒ: ๐ ๐ฎ๐ด๐ป๐ฒ๐๐ถ๐ฐ ๐ช๐ฒ๐ฑ๐ด๐ฒ ๐ ๐ถ๐ด๐ฟ๐ฎ๐๐ถ๐ผ๐ป
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 gapโcreating a massive risk of phase-to-phase or phase-to-ground flashover if metallic debris bypasses the ground wall insulation.
๐ง๐ต๐ฒ ๐๐ถ๐น๐ฒ๐บ๐บ๐ฎ: ๐ฃ๐ฎ๐ฟ๐๐ถ๐ฎ๐น ๐ฅ๐ฒ-๐ช๐ฒ๐ฑ๐ด๐ถ๐ป๐ด ๐๐. ๐๐๐น๐น ๐ฅ๐ฒ๐๐ถ๐ป๐ฑ
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.
๐ง๐ต๐ฒ ๐ฆ๐ผ๐น๐๐๐ถ๐ผ๐ป & ๐๐ผ๐๐ ๐๐๐ผ๐ถ๐ฑ๐ฎ๐ป๐ฐ๐ฒ
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 coilsโsaving 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.
