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Manufacturing Process

Core slitting
The core is made out of high quality cold rolled grain oriented (CRGO) electrotechnical steel. After incoming quality inspection the rolls are slit into strips with the required width.
Core winding
The strips are wound on special tools to the necessary core thickness.
Core annealing
Annealing of the cores takes place in a tunnel furnace with a temperature 810 +10 oC. This allows precise control of the cores mechanical dimensions and magnetic properties.
Core "impregnation"
The cores are immersed in special enamel under vacuum and cured subsequently to become a single solid part.
Core cutting
Cores are then split on a special machine, using carefully selected cutting tools and coolant to obtain burr-free edges and low core losses.
Coil winding
Primary coils are wound on precise machines from profiled rectangular enameled wires or copper strip with specially formulated insulation between the adjacent winding (patent pending), depending on the power and voltage of the transformer.
Secondary coil
Secondary coil is machined from a special copper tube with the necessary cross section and connections for water cooling.
Coil assembly
Primary and secondary coils are assembled together with suitable insulation between them withstanding breakdown voltage of at least 5 KV. Spacer blocks are inserted where necessary for the resin to penetrate everywhere.
Transformer assembly
The coil assembly and the cores are assembled together, tested at no-load conditions, and then the end frames and all other parts are fixed together and adjusted for the necessary dimensions in a jig. The finished assembly is sealed hermetically with a specially designed compound (not containing silicones) to prevent the epoxy resin from flowing out of the transformer.
Epoxy potting
The transformer assembly is preheated and then transferred to the vacuum chamber. Through a flexible tube the preheated epoxy resin is fed at the bottom of the transformer assembly, so that its rising level embosses the remaining air from the assembly. The transformers remains in the chamber hours until air bubbles stop boiling, and is transferred to the first curing oven.
Transformer curing
The potted transformers are cured during 4 hours at 80 oC and then another 4 hours at 120 oC to achieve optimum mechanical and electrical strength of the epoxy resin.
The finished transformers undergo 100% final testing of all relevant electrical parameters (voltage ratio, magnetizing current, no-load losses, short circuit impedance, current monitor ratio etc.), including hour test under load. Special tests can be conducted as agreed with the customer.

The ITF series welding transformers are delivered worldwide at very competitive prices. The vacuum epoxy potting process, developed for their manufacturing is used for other products as well, if the customer so wishes.

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