Can the transformer be overloaded?


Release time:

2023-09-14

Generally speaking, the current specified on the nameplate of the transformer is its maximum allowable safe current. If it exceeds this value, it is an overload operation state. Long-term overloading will increase the temperature of the transformer, accelerating the aging of the insulation and affecting its lifespan. Research results have proven that when the temperature of the insulation during operation increases by 8°C, its lifespan will be reduced by half.

Generally speaking, the current specified on the nameplate of the transformer is its maximum allowable safe current. If it exceeds this value, it is an overload operation state. Long-term overloading will increase the temperature of the transformer, accelerating the aging of the insulation and affecting its lifespan. Research results have proven that when the temperature of the insulation during operation increases by 8°C, its lifespan will be reduced by half.

Transformer temperature vs. power percentage curve

However, in most actual operations, the load of the transformer is not stable and changes with the peak and valley periods of day and night power consumption and seasonal temperature changes. Therefore, within a certain range of time, its overload will not affect the use of the transformer, that is, the transformer can be overloaded during peak load and winter. The allowable overload value and time can be determined based on the load curve of the transformer, the temperature of the surrounding cooling medium, and how much load the transformer has carried before overloading.

For factory operation, the load factor of the transformer should not exceed 85%. Because the load of electrical equipment fluctuates at any time, if it exceeds 85%, the transformer will fail when some machines that will bring inrush current (such as large welding machines, cranes, punch machines, high-power motors) are started. The remaining margin is used to cope with the inrush current brought by these machines, causing a significant reduction in the service life of the transformer.

Measures to prevent overload hazards

In production, we can take the following measures to prevent the harm caused by long-term overloading of transformers:

1. Reasonably allocate loads, optimize production processes, allow electrical equipment to be used in an orderly manner, and reduce simultaneous usage.

2. Appropriately increase the low-voltage side output voltage by one level (+2.5%). Since the transformer is close to full load, the voltage at the output end of the transformer will inevitably decrease, which will lead to a lower voltage of the electrical equipment at the end. This will lead to excessive active current and increase power loss. Increasing the voltage can reduce the current.

3. Improve power factor. High load rates will also lead to insufficient reactive power compensation capabilities. Power capacitors that have attenuated capacity should be replaced regularly, and reactive power compensation devices should be installed on-site for large inductive loads to improve the power factor and thereby enhance the active output capability of the transformer. To reduce the operating current and power loss, it can effectively reduce the load current and power loss, thereby reducing the load factor of the transformer.

4. Do a good job in cooling down the transformer. The temperature of the transformer will increase when operating at a high load rate. Air conditioners can be installed or forced exhaust measures can be added to cool the transformer, thereby reducing losses, improving efficiency and protecting the transformer.

5. Arrange personnel on duty to regularly inspect the operating status of the transformer, record the operating current of the transformer, and measure the temperature of the transformer, so that hidden dangers can be discovered and dealt with early!

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