Final Inspection for Stacked/Laminated Cores
1. Dimensional & Visual Check: Verify core window dimensions, core leg center distance, overall height, and stacking alignment. Inspect for burrs, rust, contamination, physical damage, and misaligned laminations ("staggered laps").
2. Tightness & Flatness Check: Ensure the core is tightly clamped. Check for loose laminations or protruding edges. Verify the flatness of the yoke and leg surfaces.
3. Core Joint (Gap) Inspection:This is a critical check for stacked cores. Measure gap sizes at multiple step-lap joints using a feeler gauge. Gaps must be within strict limits (e.g., < 0.3mm) to control exciting current and loss.
4. Insulation Resistance Tests Interlamination:Spot-check insulation between randomly selected adjacent laminations using a low-voltage ohmmeter. Core-to-Ground: Measure insulation resistance (> 500 MΩ) between the core stack and the clamping frames, bolts, and structural steel.
5. No-Load Test (Performance Verification):The ultimate functional test. Assemble the core with temporary bolts/clamps (if final hardware isn't installed). Wind temporary excitation coils around the core legs. Apply sinusoidal voltage at rated frequency to achieve rated flux density. Measure the no-load loss and exciting current. Results must be within accepted tolerance (e.g., +15%) of design values.
