How to repair transformers the hands?
Transformers consist of the core assembled from the metal thin plates (usually Sh-shaped form) isolated by varnish, and the framework with windings from the enameled copper wire. For the purpose of reduction of hysteresis losses of the plate are produced from special transformer steel or alloy of permalloy.
Transformers, especially power, bear the permanent electric and heat load. If calculation and the izgotovyoleniye of transformers are executed with deviations, the napriyomer of the ration of conductors is carried out with acid flyuyosa, then reliability of the manufactured transformers decreases and they are more often than other winding products otkazyyovat in work.
The most characteristic malfunctions of transformers sleyoduyushchy: violation of soldering in places of accession of the ends of output conductors, internal breaks of windings, the zamyyokaniye of windings among themselves and on the body.
Prepare winding wires, the flexible montazhyony wire for conclusions, the laying cable bumayoga or the thin ftoroplastovy insulating film, the kembrikovy cloth, threads, shellac varnish, the soldering iron, solder, acid-free gumboil, the fine-grained emery paper or the cloth.
For determination of nature of fault of the transforyomator unsolder the wires brought to it, and all unsoldered conductors note labels further not to mix connection.
Identification of malfunctions is made by external survey and check in the following order:
- ohmmeter check integrity and resistance of windings;
- the megger check insulation resistance between windings and between the body (core) and obmotyoka;
- the alternating current voltmeter check tension on conclusions of secondary winding at the rated napryayozheniye on primary winding;
- the alternating-current milliammeter check the current intensity of no-load operation of the transformer.
When fault is revealed, the transformer is razbiyorat, i.e. remove mounting parts and delete core plates. Do it carefully as the bent plates will complicate further assembly of the core. Plates from permalloy cannot be subjected to blows, bends and other deformations which worsen magnetically conductive properties of permalloy plates that can be reflected in further operation of the transformer.
If data on winding data are absent, then windings which should be removed unwind on the winding machine with the counter to determine number of rounds. Diameter of the wire is determined by the micrometer. If namotochyony data are available, the wire can be cut off, without having damaged, however, operational windings and the framework.
If during the work the transformer heated up over admissible rated temperature, it is necessary to be convinced that isolation of the windings left without rewind is high-quality: paper laying between layers does not contain slightly burned places (have no darkening), and the enamel covering on the winding wire keeps strongly.
In the transformers manufactured by the priborostroitelyyony plants, connections of the ends of windings to output conductors when winding are isolated by the thin ftoroplastoyovy film; each winding after wrapping by its film and glueings of the film ties round the thread by which output conductors are odnoyovremenno fixed. Winding poyoluchatsya quite rigid, and impregnation does the coil of the winding of firmer. Therefore, especially at thin wires, unwinding of the winding for the account of number of rounds is connected with difficulties, and it is necessary to show big care not to tear the wire at reeling.
Winding conduct the round to the round. In this case windings will take much less places, than at chaotic winding, and there will be the minimum possibility of breakdown between rounds. Having finished the row from right to left, conduct winding of the sleyoduyushchy row in the opposite direction. After each number (layer) of the wire stack paper laying or the ftoroplastovy film which have to enter densely on width between framework cheeks. It is impossible to allow hits of the wire between laying and the cheek of the framework. Winding thickness turn out a little bigger in that place where output conductors therefore they need to be placed from that party of the coil which after assembly of the core will be located not inside, and outside of it are located. Conclusions pass through the made openings in framework cheeks.
The enameled wire used for winding has to be covered with the continuous uniform layer of the enamel film which surface has to be smooth, brilliant, without bubbles, foreign matters, without mechanical damages of upper metal layers. The wire undertakes the same diameter and keep former number of rounds, otherwise to it not to take place in the framework.
Having reeled up all windings, the transformer coil for are sewn up from mechanical damages and dust paste over from above with the new kembrikovy tape or the film shot from the transformer before its unwinding.
Before assembly of the core check the condition of plates, straighten bent. If on iron plates имеются rust traces, then clean them and cover with the lamina of bakelitovy varnish. At assembly in the framework of the coil insert the average branch of the Sh-shaped plate, extreme leave outside of the coil. Assembly is conducted so that plates were established in turn (with one, on the other side of the coil) that is necessary for creation of the closed magnetic flux in the core.
Assembling the core, pay attention to crumpling the plate and at the same time not to damage the coil framework. Plates from transformer iron rigider and when stuffing the core are seldom rumpled. Plates from permalloy thinner therefore are quite often rumpled, bent that complicates assembly. The last 2-3 plates establish into place by easy blows of the wooden hammer. Then the core is pressed out in the vice and in addition by means of blows of the wooden hammer establish 2-3 more plates. If plates are filled leaky, then at inclusion the transformer will hoot.
Upon termination of assembly, insert fixing bolts and pull together the core.
For increase vlago-, heat stabilities, the breakdown and mechanical strength of windings of the transforyomator make impregnation of windings insulating melamine-gliftalevym ML-92 varnish viscosity 30-40 with on the viscometer funnel with the diameter of the opening of the nozzle of 4 mm in the following order:
- clean the transformer from dust then progreyovat in the drying cabinet at the temperature (120 ±10) °C within 3 hours;
- cool the transformer to 60 °C and grease with PVSG paste the output ends of windings (preparation and use of paste see below);
- submerge the transformer in the vessel with izolyatsionyony ML-92 varnish and keep in varnish of 15-20 min. before the termination of allocation of vials of air from the obyomotka;
- delete the transformer from liquid and allow to flow down to varnish within 60 min. then remove paste from output conductors;
- wipe frameworks, the core and conclusions of the transformayotor with the gauze moistened with mix of toluene and white spirit or one toluene;
- the output ends of windings are oiled transformatoryony, castoric or instrument;
- the transformer is placed in the drying cabinet and nagreyovat consistently according to the following schedule (the tolerance of temperature of ±10 °C):
|Temperature, °C||40||60||Drying time, h||2|
The general time of drying is 24 h.
Completely collected transforyomator comes to impregnation.
Upon termination of drying connect the electric power supply to the transformer and make check of tension on its windings, integrity of windings, insulation resistances, current of no-load operation.
Check also whether the transformer not strongly hoots that can be the consequence not only weak stuffing of the core, but also its insufficient tightening.
PVSG paste for protection of current leads at impregnation and varnishing.
Structure: 11% of polyvinyl alcohol of PVS, 26% of alcohol of rectificate of ethyl, 11% of the glycerin distilled by 52% of the water distilled.
Way of preparation
In glasswares mix ethyl alcohol with water. Add consistently polyvinyl alcohol and the distilled glycerin at careful hashing to the divorced ethyl alcohol the glass stick. Heat mix on the water bath at the temperature up to 90 °C during 1-2 h. Paste has to be homogeneous, without lumps and mechanical impurity. If necessary filter paste through the gauze. To store in the flask with the ground-in stopper. The expiration date - 10 days.
Application: apply paste with the brush on those places of wires or parts which are not subject to impregnation or varnishing. Then dry the put paste layer on air within 30 min. After removal of the impregnated part from varnish and running off of varnish, i.e. the actual drying of the part on air, paste is removed tweezers or the knife (not to damage the wire!).Top