What are the causes of a loose transformer core?

If there is no fixing adhesive, the causes are as follows:

(1) The burrs around the edges of the silicon steel sheets are too large, and the stacking lap gap fails to meet the specified requirements.

(2) Errors in sheet arrangement cause missing sheets or overlapping tabs, resulting in an insufficiently compressed core after stacking.

(3) Waviness or bending in the core laminations prevents them from being clamped tightly after compression.

(4) Poor material quality of the epoxy resin glass fiber tape used for binding the yokes and core, improper processing techniques, insufficient binding tension, and failure to cure into a solid monolithic structure all lead to loose bindings, aging of the binding hoops, and subsequent faults, ultimately causing the core to loosen.

(5) The clamping bolts on the structural clamps were not tightened properly, or anti-loosening washers were omitted. During operation, electromagnetic vibrations cause the bolts to loosen, which subsequently loosens the core and may also cause the grounding copper strips to fall off.

(6) If the clamping bolts are not fully tightened or there is slight vibration noise, use a large wrench to retighten the bolts until the noise is eliminated; if the noise persists, further measures must be taken.

(7) For noise caused by a small number of missing sheets, overlapping tabs, waviness, bending, or damaged silicon steel sheets, retighten the clamping bolts or insert cardboard shims before tightening again. If the noise disappears, this is sufficient; otherwise, the core must be disassembled to reselect the silicon steel sheets, followed by restacking and recompression. When selecting silicon steel sheets, those that should be stacked in pairs but have single sheets mistakenly inserted, or those stacked in threes, must all be corrected to a two-sheet stack. Select laminations of uniform thickness; discard bent, damaged, or severely wavy sheets. Silicon steel sheets with excessive burrs must be deburred before restacking, ensuring the burr height is less than 0.03 mm.

(8) In cases where the epoxy resin glass fiber tape binding hoops are damaged, aged, or loose, they must be entirely rebound using qualified materials. During the binding process, first apply temporary steel hoops to secure the core tightly. After the binding reaches a certain thickness, bake it for curing. Once cured into a rigid monolithic structure, remove the temporary steel hoops.