Transformers for supplying control and signaling circuits consist of a core assembled from thin metal plates insulated with varnish (usually W-shaped), and a frame with windings made of enameled copper wire. In order to reduce hysteresis losses, plates are made of special so-called transformer steel or permalloy alloy.
Transformers, especially power ones, carry a constant electric and thermal load. If the calculation and manufacture of transformers is made with deviations, for example, the soldering of conductors is carried out with acid fluxes, then the reliability of the manufactured transformers decreases and they often fail to work more than other winding products.
The most typical transformer malfunctions for powering the control and signaling circuits are as follows: violation of soldering at the points where the ends of the output conductors are connected, internal breaks of the windings, windings shorted to each other and to the housing. Now that Surplec offers repair and/or remanufacturing solutions you can have the best deal now.
Procedure for repairing transformers for control circuits
Prepare winding wires, flexible mounting wire for leads, cushioning cable paper or a thin fluoroplastic insulating film, cambric cloth, threads, shellac lacquer, soldering iron, solder, acid-free flux, fine-grained sandpaper or cloth.
To determine the nature of the transformer malfunction for the control and signaling circuits, the wires connected to it are soldered, and all the soldered conductors are marked with tags so as not to confuse the connection in the future.
Transformer repair for power supply of control and signaling circuits
The transformer malfunctions are detected by external inspection and verification in the following order: the integrity and resistance of the windings are checked with an ohmmeter, the insulation resistance between the windings and between the casing (core) and the windings is checked with an ohmmeter, the voltage at the terminals of the secondary windings is checked at a rated voltage on the primary winding , with an alternating current milliammeter, check the open circuit current of the transformer.
Rewinding transformer windings of control and signaling circuits
If there is no information about the winding data, then the windings to be removed are unwound on a winding machine with a counter to set the number of turns. The diameter of the wire is determined by a micrometer. If winding data is available, the wire can be cut without damaging, however, serviceable windings and the frame.
Transformer repair for power supply of control and signaling circuitsIf during operation the transformer was heated above the permissible nominal temperature, you need to make sure that the insulation of the windings left without rewinding is benign: paper linings between the layers do not contain burnt spots (do not have darkening), the enamel coating on the winding wire holds firmly.
In low-power transformers, the connections of the ends of the windings to the output conductors during winding are insulated with a thin fluoroplastic film, each winding after wrapping it with a film and gluing the film is tied with a thread, which simultaneously holds the output conductors. The winding is quite stiff, and besides, the impregnation makes the winding coil even more rigid. Therefore, especially with thin wires, the unwinding of the winding for counting the number of turns is difficult and great care must be taken not to break the wire when winding.