{"id":10840,"date":"2026-08-29T23:43:11","date_gmt":"2026-08-29T15:43:11","guid":{"rendered":"https:\/\/q8bbzjnpm5.wpdns.site\/?p=10840"},"modified":"2026-08-29T23:43:11","modified_gmt":"2026-08-29T15:43:11","slug":"quality-control-points-and-optimization-paths-of-power-transformer-manufacturing-process","status":"publish","type":"post","link":"https:\/\/subian-electric.com\/fr\/news\/quality-control-points-and-optimization-paths-of-power-transformer-manufacturing-process\/","title":{"rendered":"Points de Contr\u00f4le Qualit\u00e9 et Voies d'Optimisation du Processus de Fabrication des Transformateurs de Puissance"},"content":{"rendered":"

Un transformateur avec une r\u00e9sistance d'enroulement dans 0.5% entre les trois phases, dont l'isolation en papier a \u00e9t\u00e9 s\u00e9ch\u00e9e conform\u00e9ment aux exigences (0.5% d'humidit\u00e9 ou moins) et a subi des tests de pertes \u00e0 vide qui confirment les niveaux garantis dans 3%, survivrait et fonctionnerait pendant de nombreuses ann\u00e9es. En revanche, un transformateur construit par des fabricants n\u00e9gligents et qui n'a pas \u00e9t\u00e9 correctement s\u00e9ch\u00e9 et dont les noyaux n'ont pas \u00e9t\u00e9 serr\u00e9s cesserait de fonctionner apr\u00e8s seulement quatre ans d'exploitation. La gestion de la qualit\u00e9 des transformateurs de puissance garantit que trois types diff\u00e9rents de mat\u00e9riaux (acier, cuivre ou papier) sont assembl\u00e9s en un transformateur hautement fiable.<\/p>\n

L'objectif principal de cet article est d'expliquer o\u00f9 se situent les points de contr\u00f4le dans les processus de production des transformateurs \u2014 il s'agit des inspections entrantes des mat\u00e9riaux, de l'assemblage des noyaux et des enroulements, du s\u00e9chage sous vide et du remplissage d'huile des transformateurs ainsi que des tests finaux des produits.<\/p>\n

R\u00e9ponse courte : Le processus de contr\u00f4le de la qualit\u00e9 pour la fabrication de transformateurs se compose de cinq points principaux de contr\u00f4le de la qualit\u00e9 : inspection des mati\u00e8res premi\u00e8res, production du noyau et de l'enroulement, s\u00e9chage sous vide et impr\u00e9gnation \u00e0 l'huile de la bobine, assemblage du transformateur et tests d'acceptation en usine selon la norme IEC 60076-1. Les principaux crit\u00e8res pour les contr\u00f4les de qualit\u00e9 incluent le rapport de transformation du transformateur dans \u00b10.5%, la d\u00e9viation du rapport de chute de tension en dessous de 2%, et les pertes \u00e0 vide et sous charge selon IEC 60076-1 (\u00b110% \u00e0 +15%).<\/p><\/blockquote>\n

\"Quality<\/p>\n

\n

Qu'est-ce que le contr\u00f4le de qualit\u00e9 dans la fabrication de transformateurs ?<\/h2>\n

Dans la fabrication de transformateurs, le contr\u00f4le de qualit\u00e9 signifie une s\u00e9rie de v\u00e9rifications, de mesures et de points de contr\u00f4le planifi\u00e9s qui garantissent que l'unit\u00e9 sera capable d'efficacit\u00e9 \u00e9lectrique, thermique et m\u00e9canique pendant au moins 25 \u00e0 40 ans de dur\u00e9e de vie pr\u00e9vue. Il est important de souligner que le contr\u00f4le de qualit\u00e9 n'est pas la m\u00eame chose que les tests. Les tests d\u00e9tectent les d\u00e9fauts, tandis que le contr\u00f4le de qualit\u00e9 les pr\u00e9vient. Ainsi, une usine qui a d'excellents tests finaux mais un contr\u00f4le de processus faible identifie simplement les probl\u00e8mes \u00e0 la fin du processus, lorsque les corrections sont les plus co\u00fbteuses. Une usine avec un contr\u00f4le de processus strict produit des produits stables \u00e0 faibles co\u00fbts de rebut, c'est pourquoi les meilleurs fabricants chinois et internationaux consid\u00e8rent le CQ comme une technologie de production plut\u00f4t qu'un d\u00e9partement d'inspection finale.<\/p>\n

La base des normes est IEC 60076-1 (exigences g\u00e9n\u00e9rales et tests) compl\u00e9t\u00e9e par IEC 60076-3 (niveaux d'isolation), IEC 60076-5 (degr\u00e9 de r\u00e9sistance au court-circuit) et IEC 60076-10 (niveau sonore). Les acheteurs doivent \u00e9galement \u00eatre inform\u00e9s que la majorit\u00e9 des usines fiables utilisent un syst\u00e8me de gestion de la qualit\u00e9 ISO 9001 en plus des normes de produit.<\/p>\n

Le processus de fabrication : o\u00f9 la qualit\u00e9 est faite ou perdue.<\/h2>\n

Un transformateur de puissance immerg\u00e9 dans l'huile standard implique environ 10 \u00e9tapes et chaque \u00e9tape a son propre mode de d\u00e9faillance si quelque chose ne va pas dans le processus. Les laminations du noyau sont d\u00e9coup\u00e9es et empil\u00e9es selon un facteur d'empilage contr\u00f4l\u00e9 et une pression de serrage, et si elles sont surmen\u00e9es ou si de la corrosion est pr\u00e9sente entre les feuilles, les pertes \u00e0 vide augmentent et des points chauds se produisent sur le noyau. Les enroulements sont cr\u00e9\u00e9s \u00e0 partir de fils de cuivre ou d'aluminium qui sont \u00e9galement sous tension contr\u00f4l\u00e9e et isolation de couche, et un seul papier intercal\u00e9 in\u00e9gal peut entra\u00eener des d\u00e9charges partielles. La partie active est s\u00e9ch\u00e9e dans une chambre \u00e0 vide afin d'\u00e9liminer l'humidit\u00e9, ce qui est le premier point de contr\u00f4le de qualit\u00e9 dans le processus en cours. Ensuite, le r\u00e9servoir cr\u00e9e un vide et le remplit d'huile d\u00e9gaz\u00e9e et s\u00e9ch\u00e9e, et la derni\u00e8re partie du processus est l'ex\u00e9cution des tests en usine.<\/p>\n

Le transport est \u00e9galement un point de contr\u00f4le de qualit\u00e9, car un transformateur pourrait subir des dommages r\u00e9sultant de chocs et d'inclinaisons. Une solution au probl\u00e8me est la norme IEC 60076-11 qui sugg\u00e8re d'exploiter des enregistreurs de chocs et d'inclinaisons dans de grandes turbines. Le lecteur trouvera les meilleurs points de contr\u00f4le dans les paragraphes suivants.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n
\u00c9tape du processus<\/th>\nM\u00e9thode de CQ<\/th>\nCo\u00fbt de la d\u00e9faillance si non v\u00e9rifi\u00e9<\/th>\n<\/tr>\n<\/thead>\n
R\u00e9ception des mat\u00e9riaux<\/td>\nCertificats du fournisseur + tests al\u00e9atoires<\/td>\nFaible \u2014 d\u00e9tect\u00e9 t\u00f4t<\/td>\n<\/tr>\n
D\u00e9coupe\/empilage du noyau<\/td>\nContr\u00f4le de la taille de l'emprunt, v\u00e9rification du facteur d'empilage<\/td>\nMoyen \u2014 pertes \u00e0 vide plus \u00e9lev\u00e9es<\/td>\n<\/tr>\n
Construction des enroulements<\/td>\nCompte des tours, v\u00e9rifications de tension, r\u00e9sistance<\/td>\n\u00c9lev\u00e9 \u2014 tours court-circuit\u00e9s, points chauds<\/td>\n<\/tr>\n
S\u00e9chage sous vide<\/td>\nPoint final d'humidit\u00e9, PI apr\u00e8s remplissage<\/td>\nTr\u00e8s \u00e9lev\u00e9 \u2014 d\u00e9faillance pr\u00e9matur\u00e9e<\/td>\n<\/tr>\n
Assemblage et mise en cuve<\/td>\nEnregistrements de couple, inspection des joints<\/td>\nMoyen \u2014 fuites, pi\u00e8ces l\u00e2ches<\/td>\n<\/tr>\n
Tests en usine<\/td>\nBatterie de routine IEC 60076-1<\/td>\n\u00c9lev\u00e9 \u2014 d\u00e9viations de garantie manqu\u00e9es<\/td>\n<\/tr>\n
Emballage et transport<\/td>\nEnregistreurs de chocs\/inclinaisons, plan de manutention<\/td>\n\u00c9lev\u00e9 \u2014 dommages en transit<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Point de contr\u00f4le 1 : Inspection des mat\u00e9riaux entrants<\/h2>\n\n\n\n\n\n\n\n\n\n
Mat\u00e9riau<\/th>\nM\u00e9thode d'inspection<\/th>\nCrit\u00e8res d'acceptation typiques<\/th>\nCons\u00e9quence d'un mauvais mat\u00e9riau<\/th>\n<\/tr>\n<\/thead>\n
Acier au silicium orient\u00e9 grain<\/td>\nTest des propri\u00e9t\u00e9s magn\u00e9tiques selon ASTM A876 \/ IEC 60404<\/td>\nPertes totales sp\u00e9cifiques \u2264 limite du catalogue ; rev\u00eatement intact<\/td>\nPertes \u00e0 vide plus \u00e9lev\u00e9es, classe d'efficacit\u00e9 inf\u00e9rieure<\/td>\n<\/tr>\n
Conducteur en cuivre \/ aluminium<\/td>\nV\u00e9rification de la r\u00e9sistivit\u00e9 et des dimensions<\/td>\n\u2265 99.9% conductivit\u00e9 Cu ; tol\u00e9rance de diam\u00e8tre \u00b10.5%<\/td>\nPertes de charge plus \u00e9lev\u00e9es, points chauds<\/td>\n<\/tr>\n
Papier d'isolation et carton press\u00e9<\/td>\nDensit\u00e9, r\u00e9sistance \u00e0 la traction, teneur en humidit\u00e9<\/td>\nDensit\u00e9 0.9\u20131.2 g\/cm\u00b3 ; humidit\u00e9 selon sp\u00e9cification<\/td>\nRisque de PD, faiblesse m\u00e9canique<\/td>\n<\/tr>\n
Huile isolante<\/td>\nDielectric strength (IEC 60156), water content, DGA<\/td>\nBDV \u2265 40 kV, water < 20 ppm (new oil)<\/td>\nLower withstand, accelerated aging<\/td>\n<\/tr>\n
Bushings & tap changers<\/td>\nVisual, insulation resistance, tan delta, gas tightness<\/td>\nPer supplier test certificates and spot re-test<\/td>\nBushing flashover, OLTC failure<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Serious manufacturing companies have close oversight of the materials they bring in based on supply specifications and not just on brand names. For instance, steel coils vary in composition and quality from one coil to another even when coming from the same manufacturer. This means that a company that keeps track of every reel and chooses steel based on real characteristics of the metal rather than a stamp is already achieving quality at the lowest cost.<\/p>\n

Control Points 2\u20133: Core & Winding Fabrication<\/h2>\n\n\n\n\n\n\n\n\n\n\n
Stage<\/th>\nKey Checks<\/th>\nCrit\u00e8res d'acceptation typiques<\/th>\n<\/tr>\n<\/thead>\n
Core cutting & stacking<\/td>\nStacking factor, burr height, clamping pressure, lamination insulation<\/td>\nStacking factor \u2265 0.95; burr < 0.02 mm; no shorted laminations<\/td>\n<\/tr>\n
Core assembly & banding<\/td>\nClamping torque, core ground connection, bolt insulation<\/td>\nSingle-point core ground; insulation resistance between laminations > 100 M\u03a9<\/td>\n<\/tr>\n
Winding conductor & insulation<\/td>\nConductor tension, paper wrap continuity, layer insulation placement<\/td>\nNo bare conductor exposure; continuous layer insulation<\/td>\n<\/tr>\n
Winding disc \/ layer build<\/td>\nTurn count, transposition, cooling duct alignment<\/td>\nTurn count verified against design; ducts clear and uniform<\/td>\n<\/tr>\n
Coil pressing & clamping<\/td>\nAxial pressure, coil height consistency<\/td>\nPressure within design window; height variation < 1 mm across phases<\/td>\n<\/tr>\n
Tap changer & lead connections<\/td>\nBrazing\/soldering quality, insulation distance, torque<\/td>\nLow-resistance joints; verified clearances per insulation level<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

There are two important aspects related to this. First and foremost, winding resistance imbalance between the phases must be maintained at the time of manufacturing to ideally less than 2%. Otherwise, an improper transposition of a parallel conductor system appears in the form of circulating currents and hot spots in the system operating under the load. Another thing is core clamping pressure which should be neither too loose nor too tight. A loose configuration results in a humming core, while a tight one causes insulation of the laminations to get crushed. The problem here can be solved through the process of measurement in the course of production.<\/p>\n

\"Control<\/p>\n

Control Point 4: Vacuum Drying & Oil Impregnation<\/h2>\n

Moisture is the main menace for a transformer, and it is either eliminated or let into the active winding in the course of the drying and oil-filling operation. Paper is dried in a vacuum oven (at temperature usually reaching a minimum of 100\u2013130 \u00b0C with distribution units and even higher temperatures for large units in deep vacuum below 50 Pa or 0.5 mb) until moisture drops to less than 0.5% (in mass fraction), having its quality verified by Karl Fischer or dew point measurement. After that, oil is filled into the tank and the impregnation process is completed without any bubbles being left inside the paper \u2014 all bubbles are dangerous sources of potential discharge.<\/p>\n

This process is usually rushed when the drying time is reduced. A properly dried and impregnated transformer usually takes several days to dry, e.g. a 10 MVA transformer takes at least 2\u20134 days to dry in a drying process and 1 day for vacuum filling. Factories that hurry with this process save money now but will face problems later. The correctness of the drying process can be checked using insulation resistance and polarization index measurements after the filling process is completed. A polarization index above 2.0 ensures that paper is dry, whereas a value below 1.5 means that there is humidity left.<\/p>\n

Control Point 5: Factory Acceptance Testing<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Test<\/th>\nStandard Reference<\/th>\nCrit\u00e8res d'acceptation typiques<\/th>\n<\/tr>\n<\/thead>\n
Turn ratio test (all taps)<\/td>\nIEC 60076-1<\/td>\nWithin \u00b10.5% of design ratio<\/td>\n<\/tr>\n
Winding resistance<\/td>\nIEC 60076-1<\/td>\nPhase imbalance \u2264 2%; corrected to reference temperature<\/td>\n<\/tr>\n
Insulation resistance \/ PI<\/td>\nIEEE 43 \/ IEC 60076-1<\/td>\nPI \u2265 2.0 for oil-immersed units<\/td>\n<\/tr>\n
No-load loss & current<\/td>\nIEC 60076-1<\/td>\nWithin tolerance: loss +15% (and \u221210%) on guaranteed value per IEC<\/td>\n<\/tr>\n
Load loss & impedance<\/td>\nIEC 60076-1<\/td>\nLoad loss within +15%; impedance within \u00b17.5%<\/td>\n<\/tr>\n
Dielectric tests (LI, AC, applied)<\/td>\nIEC 60076-3<\/td>\nNo flashover or breakdown at specified levels<\/td>\n<\/tr>\n
Mesure des d\u00e9charges partielles<\/td>\nIEC 60270<\/td>\nTypically < 100 pC at 1.1\u00d7 rated voltage for HV units<\/td>\n<\/tr>\n
Temperature rise test<\/td>\nIEC 60076-2<\/td>\nWinding rise \u2264 65 K (class A), oil rise \u2264 60 K (typical)<\/td>\n<\/tr>\n
Sound level test<\/td>\nIEC 60076-10<\/td>\nPer agreed value; often 55\u201370 dB(A) for distribution units<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The factory testing procedure serves as the main evidence for the buyer that the product meets its warranty requirements. A full test on 10MVA transformer usually requires about 2-5 days and usually is already included in the cost of the device; however, requesting a witnessed test (either by the buyer himself or a third party) will involve some logistics but will provide much more peace of mind. It is important to note that IEC 60076-1 allows for some positive loss tolerance, which means that the manufacturer can provide losses that are somewhat greater than the loss guarantee level. Thus, negotiating the loss guarantees and checking the numbers tested is a good commercial tool, not just a formality.<\/p>\n

Optimization Paths: Lean, Automation & Digital QC<\/h2>\n

The contemporary manufacturing industry seeks to maintain a high level of quality while at the same time reducing costs, utilizing various tactics. One of them is the process of lean production, which adopts methods that enable companies to diminish material transportation, create uniform work processes and implement 5S technique exclusively throughout all its stations. Moreover, this methodology enables companies to minimize the number of manual errors. For instance, production process automation of such procedures as cutting, winding process control and brazing provides factories with an opportunity to eliminate the influence that manual labor has on the final productivity. For instance, machines that perform the winding process keep tension in wires constantly within \u00b13% tolerances as opposed to doing this manually.<\/p>\n

The third method is the use of digital quality records. Compared to using visual tests on paper, factories prefer to keep all the necessary information in databases, which allows identifying issues beforehand. Basically, this is the area Chinese companies focused on significantly during their production process. The latest machines can track the number of turns, torque, drying process and quality and ensure a quality check for every product from the very beginning. The practical suggestion for customers would be to ask for the digital traceability summary and quality check documents as it will tell them more about the factory than any promotion materials.<\/p>\n

\"How<\/p>\n

How to Audit a Transformer Factory<\/h2>\n

If you’re purchasing several pieces of equipment you should know that factory audits are definitely worth much more than their cost. You should have a small checklist with you and search for actions rather than for papers. First, it is necessary to inspect the materials warehouse: whether steel is kept dry and sheltered, was oil kept either under nitrogen or in a tight container. Secondly, it is time to check the drying line: require for the real records of the drying cycle of the last piece of equipment and make sure vacuum and time periods are according to the specifications. Thirdly, you should check the quality control stations: do the records account the number of rotations and resistance on the computer or paper. Fourthly, you should check the testing floor: does the factory use the full IEC 60076-1 tests and could you watch the performance of the test? Fifthly, you need to check the handling of non-conformance units: what happens with a unit that has failed tests \u2014 is it rewired accordingly or sent away unnoticed?<\/p>\n

Also, you should get references for running installations and export history which will allow you to check customs and inspection records. A factory able to present the running unit in your region, test reports, and successful practices is definitely a reliable partner but if it doesn’t have such documents it is a big risk. Jiangsu Subian Electric Power, as the IEC 60076 compliant manufacturer exporting all over the world is open for the inspection and the companies which are open for the inspection usually pass it successfully.<\/p>\n\n\n\n\n\n\n\n\n\n
Common Defect<\/th>\nRoot Cause<\/th>\nDetection Point<\/th>\nPrevention<\/th>\n<\/tr>\n<\/thead>\n
High no-load loss<\/td>\nPoor steel, burrs, crushed lamination insulation<\/td>\nCore test, no-load loss test<\/td>\nSteel loss sorting, burr < 0.02 mm<\/td>\n<\/tr>\n
Winding resistance imbalance<\/td>\nBad transposition, joint issues<\/td>\nWinding resistance test<\/td>\nControlled tension, verified transpositions<\/td>\n<\/tr>\n
Partial discharge at test<\/td>\nMoisture, bubbles, insulation damage<\/td>\nPD measurement<\/td>\nEnd-point-controlled drying, vacuum filling<\/td>\n<\/tr>\n
Leaks in service<\/td>\nWeld defects, gasket issues<\/td>\nPressure test, tank inspection<\/td>\nRobotic welding, vision inspection<\/td>\n<\/tr>\n
OLTC failure early life<\/td>\nAssembly contamination, torque errors<\/td>\nOLTC timing\/contact tests<\/td>\nClean-room assembly, guided torque tools<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Questions Fr\u00e9quemment Pos\u00e9es<\/h2>\n

What is the most important quality control step in transformer manufacturing?<\/h3>\n

The most skilled professionals are bound to name vacuum drying and oil saturation the reason for malfunctioning as moisture is responsible for a large part of failures that occur in operation. Moisture in paper must be decreased below 0.5% and oil must be processed by being degassed and treated by vacuum to form no bubbles. An organization that tries to speed up drying process saves hours on manufacturing but dooms the equipment to premature aging and potential partial discharge. The evidence is given by the index of polarization after filling. It is normal if the index exceeds 2.0, and it shows a problem if it goes below 1.5.<\/p>\n

What factory tests should I insist on before accepting a transformer?<\/h3>\n

I would recommend requiring the factory to perform a complete set of tests which include IEC 60076-1 regulation tests such as tests of turn ratio, winding resistance, insulation resistance as well as tests of losses and impedances which involves tests of dielectric strength. When you deal with transformers that are large or sensitive to noise, you should also conduct the tests of the rise of temperature and the level of noise that is generated by the new machine. In case the transformer will be used in application with risk of short-circuit existence, you will need to require short-circuit tests as well. Make sure that you know about the testing process before making the decision regarding your large purchase.<\/p>\n

How much does a factory test report cost?<\/h3>\n

Routine factory tests are regularly contained in the price of a transformer and take usually 2 to 5 days for the 10MVA transformer. Special tests such as rise checking will require extra cash that will be $2000-15000 depending on the complexity of a test. However, one should fully understand that the price of eliminating the errors that are found out after the process has already cost some money.<\/p>\n

What tolerance can I expect on guaranteed losses?<\/h3>\n

According to IEC 60076-1 regulation, the difference in the losses can be +15% to the percentage that is established in the contract for the production. Therefore, the manufacturer is allowed to underperform by maximum 15% during manufacturing stages. For the qualified factories, however, the deviation means that the values should be set rather accurately and the tolerance will have to be the lowest possible due to the importance of losses.<\/p>\n

How can I tell if a transformer manufacturer is truly IEC compliant?<\/h3>\n

Three regulations should be followed in order to be sure that you are dealing with an efficient manufacturer: check for the current ISO certification, require a statistics report of previous operations, and check the factory testing plan of the manufacturer in question which users will have to read.<\/p>\n

R\u00e9f\u00e9rences<\/h2>\n