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Specializing in the production of various El transformers, voltage rise and fall transformers, ring transformers, SG three-phase and DG single-phase dry-type transformers, regulated power supplies, special transformers
The temperature rise of transformer is directly proportional to its loss. Transformer loss includes core loss and coil copper loss. Reducing the working magnetic induction intensity of core and selecting low loss core materials are the main means to reduce core loss.
(1) Causes of short circuit between turns
1) The quality of enameled wire is poor, especially for thin wires. Pinhole points are allowed in the wire standard, and short circuits are easy to occur when winding.
2) The enameled wire is damaged during winding, such as damage to the paint film, scratches, knots, etc.
3) The pad paper is crushed or the pad is displaced.
4) There are burrs in the lead wires or solder joints, which press the insulating layer.
5) When using copper shielding, the interlayer insulation is not well-padd, so that the shielding layers touch head and tail.
6) Improper selection of insulating varnish during dipping, its solvent will corrode the enameled wire or the insulating varnish has a large shrinkage stress, and the coil shrinks when drying, causing a short circuit.
(2) Detection of inter-turn short circuit
1) Transformers should be tested for induced voltage. In order to improve the detection sensitivity, the test frequency is preferably 400HZ.
2) Detected by pulse comparison method. A high-voltage square wave is applied to both ends of the transformer winding, and the attenuation oscillation waveform of the two coils is compared to judge whether the short circuit is not.
3) Measure the no-load loss of the transformer. When the core loss is qualified, and the no-load loss increases, it means that the coil has a short circuit.
4) The Q value of a high-frequency transformer or inductor can be measured to determine whether there is a short circuit.
The methods are:
1) Use materials with small H-values
2) Appropriately reduce the magnetic induction intensity value
3) Avoid and reduce the magnetic circuit air gap
4) Prevent inter-turn short circuit
5) Reduce the internal stress of the iron core during assembly
In order to meet the judgment current requirements of the anti-electric test, it is mainly started from reducing the insulation capacitance of the transformer. The following points can be taken:
1) Increase the insulation thickness between the transformer windings and between the windings and the core.
2) Use insulating materials with low dielectric constant.
3) To prevent the transformer from getting wet, choose materials with low water absorption.
4) Double-layer or multi-layer shielding is adopted to reduce the capacitance between groups.
1) The width of the electrostatic shield is equal to the winding width of the coil.
2) The copper foil with good conductivity is used, and the toroidal transformer can be wound with a layer of enameled wire.
3) Attention should be paid to the insulation of the shielding layer at the end to prevent short circuit.
4) The insulation between the shield and the winding (including creepage distance and number of insulation layers, etc.) must meet the requirements of safety standards.
5) The lead wire of the shielding layer should be well soldered, and attention should be paid to the insulation of the lead wire.
6) When shielding with copper foil, it is necessary to prevent edge burrs from damaging the insulation and causing short circuits.
1) The coil is damp.
2) The thickness and number of layers of the insulating layer do not meet the requirements.
3) The coil margin distance and creepage distance do not meet the requirements.
4) The skeleton is cracked, allowing moisture to penetrate.
5) The coil is not dried when dipped, the insulating paint is not filmed, and the insulating resin is not cured.
6) The moisture in the coil is not removed before the coil is dipped. When the coil is dried after dipping, the insulating paint on the surface of the coil has been dried and cured, but the interior has not been cured to form a film.