【 The Role of the Conservator in Transformers 】
The conservator (oil pillow) plays a crucial role in transformers, especially in oil-immersed units. Its primary functions include:
- Oil Storage and Compensation: As the volume of transformer oil expands or contracts due to temperature changes, the conservator acts as a reservoir to store excess oil when it expands and supply additional oil when it contracts. This ensures that the oil tank remains fully filled with oil at all times.
- Reduced Air Exposure: By providing an extra volume for oil expansion, the conservator minimizes the contact between the transformer oil and air, thereby slowing down the oxidation process and extending the life of the oil.
- Monitoring Oil Level: The side of the conservator is equipped with an oil level gauge, which allows operators to monitor the oil level and ensure it remains within the safe operating range.
There are three main types of conservators:
- Waved Conservator : Features a flexible, corrugated design that can expand and contract with changes in oil volume.
- Capsule Conservator : Uses a sealed bladder or capsule inside the conservator to separate the oil from air, further reducing contamination.
- Diaphragm Conservator : Employs a diaphragm to isolate the oil from air, similar to the capsule type but often with a different material or structure.
【 Working Principle of the Transformer Breather 】
The breather (or purifier) in a transformer operates based on the temperature difference between the top and bottom layers of oil. This temperature gradient causes the oil to circulate through the breather. During this process:
- Absorption of Contaminants: Harmful substances in the oil, such as moisture, free carbon, and oxides, are absorbed by the silica gel or other desiccant materials inside the breather.
- Oil Regeneration: This absorption process helps to purify the oil, maintaining its electrical and chemical properties and effectively regenerating the transformer oil.
【 How Transformers Change Voltage 】
The voltage transformation in a transformer is based on the principle of electromagnetic induction. Here’s how it works:
Primary Winding: When alternating current (AC) flows through the primary winding, it creates a varying magnetic field around the core.
Magnetic Flux: This magnetic flux links with the secondary winding, inducing an electromotive force (EMF) in the secondary winding.
Voltage Ratio: The voltage induced in the secondary winding is proportional to the number of turns in the secondary winding relative to the primary winding. Specifically:
If the secondary winding has more turns than the primary, the output voltage is higher, resulting in a step-up transformer.
If the secondary winding has fewer turns than the primary, the output voltage is lower, resulting in a step-down transformer.
【 Autotransformers 】
An autotransformer is a special type of transformer that uses a single winding with multiple taps. It differs from a conventional two-winding transformer in the following ways:
Single Winding: The secondary winding is not isolated from the primary; instead, it is connected to one or more taps along the same winding.
Electrical and Magnetic Coupling: In addition to electromagnetic induction, an autotransformer also transfers energy directly through the shared portion of the winding.
Efficiency and Cost: Due to the reduced amount of copper and iron required, autotransformers are more efficient and cost-effective compared to two-winding transformers. They are commonly used for voltage regulation and in applications where electrical isolation is not necessary.
【 Overloading Operation of Transformers 】
Transformers are designed to operate within a specific load range, but they can sometimes be subjected to overloading conditions. The key considerations for overloading operation include:
Equivalent Aging Principle: The transformer's insulation system should not age faster than intended. Overloading periods should be balanced with periods of reduced load to ensure that the overall aging rate does not exceed the design limits.
Temperature Limits: During overloading, the hottest spot in the windings should not exceed 140°C, and the top oil temperature should not exceed 95°C.
Load Limit: The maximum overload should not exceed 50% of the rated load to prevent excessive stress on the transformer components.
