Transformer cooling ventilation

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A transformer is an electrical machine that allows electric voltage to be increased or decreased based on the theory of electromagnetic induction. Transformers are classified according to their construction and capacity, but on this occasion we will focus on the so-called Power Transformers, which can handle up to MVA. The ventilation applied to a power transformer is very important, since it is responsible for the dissipation of the heat produced and is done through a network of radiators. By having this type of cooling we prevent the insulation of the windings from melting and the transformer from short-circuiting. Here are some benefits of having proper cooling: Improve efficiency which translates into energy savings. The KVA capacity of the transformer can be increased. The life of the transformer is significantly increased. The type of cooling in this method is also known as forced draft cooling and is typically used in dry type power transformers or immersed in insulating liquid that can be oil, among others.

The equipment to be used must be a fan with certain special characteristics, since we remember that we put the entire transformer at risk, which can be damaged by overheating if the fan were to fail. Said fan must have some of the following characteristics: Be weather resistant, with a suitable coating, which can be paint or hot-dip galvanized, minimum environmental protection grade Poland Email List C It must have an overheat protection device for the motor and drain. OSHA type protection grilles. The flow must have enough dynamic pressure to completely pass through the radiator wafers, thus achieving a more uniform flow. Now, the location of the fans must be as uniform as possible, since it always presents unequal cooling, as we mentioned previously. To increase the capacity of the transformer it is necessary to increase cooling to improve convection and heat transfer. CALCULATION The next point to discuss is a simple calculation to learn how to define the adequate ventilation capacity. It must be taken into account that it is for a power transformer with wafer radiators. To achieve cooling we must increase the speed of the air passing through the radiator wafers. Passing the air at a higher velocity can be directly translated to the increase in the height of the radiator (area) and can be expressed with the following formula.



Where:Velocityadiator heighooling coefficient Example: If we put this formula into practice for a MVA transformer with a design data of °C maximum heating, and due to having poor or no ventilation, it presents an overload on the copper and the oil. This load increases the current load by % , so the increase in temperature will also be affected in proportion:  = Knowing the data, we get the same ratio at °C, which means that the transformer could reach up to °C . The above implies greater heat dissipation and an increase in the dissipation coefficient, which is affected by the relationship of factors and respectively, which result from the oil temperature correction table: With these data we can calculate the dissipation coefficient: Which means that we have a dissipation of %. As we have said before, this % depends on the increase in the area of ​​the radiators, or the % increase in the flow (and speed) of air through the radiators and we will start as follows: Wafer Through Velocity Calculation We will use the aforementioned formula: Where: H= radiator height, or the dissipation coefficient %= (this is the value that would have to increase the radiator area). Flow calculation Now that we know the speed of the air, we apply our continuity formula, in this case we must know the area of ​​the radiators. For this case we will assume that the area of ​​the radiator.