Machine Tool Transformers: Common Failure Mechanisms of Transformer Coils - isolation transformers 60kva

A transformer is a static electromagnetic device that changes electrical energy and transfers electrical energy from one circuit to another, and plays an important role in electronic equipment. For example, the AC voltage and DC voltage in the power supply equipment are almost all obtained by the transformer through transformation and rectification. In addition, most aspects of circuit isolation, matching and impedance transformation are also realized through transformers. There are many varieties of transformers, too many to list. For example: according to the classification of working frequency, it can be divided into power frequency power transformer, intermediate frequency power transformer, audio transformer, super audio transformer and high frequency transformer. According to the classification of use, it can be divided into power transformers, audio transformers, pulse transformers, switching power transformers, high-frequency transformers, special transformers, etc.

The coil constitutes the circuit part of the transformer and is the basic component of the transformer. It consists of several windings. Except for the autotransformer, the coil windings must be insulated, and the two circuits connected by the windings must also be insulated. Enameled wire is the most commonly used winding wire material, and it is also the key material that affects the quality and reliability of the transformer. When the coil is abnormal, the transformer will have poor parameters, or even open circuit or burn out. Therefore, the coil is the main test and analysis entry point in the transformer failure analysis.

Here are some common failure mechanisms related to coils (enameled wires):

01.

Enameled wire corrosion

Inside the transformer, enameled wire is used to wind the coil. During the winding process, the enameled film on the surface of the enameled wire may be slightly damaged. The various materials used in the transformer manufacturing process may contain corrosive ion pollution, such as insulating paint, glue, tape, skeleton, flux, etc. When the transformer works in a humid environment, the corrosive ions are easy to corrode the enameled wire from the damage of the enameled film, and finally cause the coil to open.

In addition, the enameled film of the enameled wire is also easily damaged due to thermal or mechanical reasons at the welding point between the lead-out end of the enameled wire and the pin. When the working environment of the transformer contains corrosive ions (such as salt spray environment), the damaged part of the enameled wire is also easily corroded.

02.

Poor insulation

When the enameled wire itself has defects (too many pinholes), or the coil is damaged during the winding process (the skeleton burr in the transformer should be controlled within a reasonable range, generally the length of the burr is not more than 1mm, and the length of the burr is too long, which can easily lead to the structure of the enameled wire. damage, higher requirements for high-reliability products), even if there are no corrosive substances that corrode the coil in the internal and external environment of the transformer, the transformer is easily burned out due to poor insulation between turns/layers of the enameled wire. When the primary and secondary coils are coaxially wound, if the insulating tape is not wrapped properly, it will also lead to breakdown failure.

03.

Power failure

Because the input voltage is too high or the design margin of the magnetic saturation point of the transformer is insufficient, it is easy to cause the magnetic saturation of the transformer and eventually lead to the overheating of the coil, which is another important reason for the failure of the transformer. Magnetic saturation occurs when the primary voltage is too high, causing the magnetic flux density to be greater than the saturation magnetic induction. After the magnetic saturation, the primary current soars and the heat generation increases, eventually causing the coil to burn out or the fuse to blow.

All kinds of components containing coils may have overcurrent failure, such as inductors, relays, etc.