The overload operation of the transformer means that the transformer exceeds the rated current value when it is running. The long-term severe overload operation of the transformer will not only reduce the efficiency of the transformer, but also increase the copper loss and cause equipment damage, which is not conducive to the economic and safe operation of the transformer.
1. Overload operation reduces transformer efficiency
The loss of the transformer mainly comes from the iron loss and copper loss inside the transformer. According to the transformer efficiency curve, when the transformer output is zero, the efficiency is also zero; when the transformer output increases, the efficiency starts to increase until the maximum value and then starts to decrease. . This is because the iron loss of the transformer basically does not change with the load, so the efficiency is low when the load is small. The copper loss is proportional to the square of the load current. When the load increases, the copper loss will increase quickly, which will reduce the efficiency of the transformer. It can be seen that the overload operation of the transformer does not cause the transformer to carry more load and output, but it is counterproductive. The output efficiency of the transformer is reduced.
Of course, overload operation of the transformer is also possible, but it is conditional. The overload capacity of the transformer is determined according to the capacity of the transformer. It can be higher than its rated load, but it is not allowed to exceed the relevant provisions of the load multiple and the allowable overload duration, and the temperature rise of the transformer cannot exceed the specified standard. According to relevant information: the lighter the overload, the allowable duration cannot exceed 30 minutes at 1.3 times.
2. The influence of overload operating temperature on the transformer
The temperature rise of the transformer has a great influence on its operation, and the most important thing is the influence on the insulation strength of the transformer. When the temperature of the transformer rises, the resistance of the coil will increase, and the copper loss will increase. At the same time, the temperature rise of the transformer will also affect the strength of the insulating material. When the transformer is produced, the materials used include iron core made of metal materials and high and low voltage coils made of insulating materials. The transformer core can withstand higher temperatures without damage, but when the temperature of the coil exceeds a certain value, there will be great damage. Especially in the midsummer season, the ambient temperature can reach 40 degrees Celsius. In the case of transformer overload operation, the temperature of the transformer will reach 100 degrees Celsius. If it is operated for a long time, the insulating material in the transformer will gradually lose its original value. Mechanical properties, the higher the temperature, the faster the insulation aging, the coil will lose the protection of the insulation layer, and the transformer will be burnt in severe cases.
1. When the transformer is connected to the load, the maximum load should not exceed the rated capacity of the transformer, so that the transformer is in normal operation and the coil insulation tends to normal speed, which can extend the running time of the transformer.
2. If the transformer runs under overload conditions, scientifically and strictly abide by the allowable multiples and allowable overload duration of the transformer under overload conditions, and the temperature should not exceed the specified standards for the transformer to avoid damage to the transformer.
3. When the transformer is configured, the highest efficiency of the transformer should be considered, and a certain amount of space should be reserved to meet the needs of the user at the maximum load, so that the output of the transformer is maximized, the loss of the transformer is the lowest, and the power supply quality and reliability. According to the basic theory of "Electrical Engineering", the highest efficiency of the transformer appears roughly when the load system is 0.5-0.6. The load of the transformer should not cause the transformer to run at full load and light load. The efficiency can be selected at 0.7, and the transformer capacity should be reserved There is a certain space to meet the needs of the transformer at the maximum load.
4. For transformers with small capacity and serious overload, load shunting or the installation of another transformer should be adopted to solve the problem. The capacity of the new transformer should be determined according to the load situation of the power supply range.