kVA Rating
kVA stands for Kilovolt-Ampere and this rating is used to rate a transformer. The kVA rating for the single-phase transformers will not be the same for the three-phase transformers. The kVA of a transformer should be equal to or greater than the rating of the load. In other words, a 1 KW load would require a 1 kVA transformer.
Primary Voltage and Secondary Voltage
Primary voltage refers to the voltage that is applied to the primary winding of a transformer. If the primary has fewer turns compared to the secondary, the step-up transformer is used to increase the voltage. And, if the primary has more turns compared to the secondary, the step-down transformer is used to decrease the voltage.
Secondary voltage is the coil winding that supplies output voltage. The output voltage varies with variations in the load resistance and even with constant voltage input.
Full Load Current
The full load current is defined as the maximum allowable current to the winding. For calculating the full load current, the voltage, kVA rating, and the type (single-phase or three-phase) are required.
Vector Type
The different vector types are approved by the International electrochemical commission and they categorize the LV windings and HV windings configuration of the three-phase transformer. The difference in winding connections produces different phase angles between the voltage of the windings.
If the transformers are connected in parallel, the vector group should be the same to avoid circulating current and other system disturbance. Dyn 11 is a vector group notation of a transformer in which LV windings in star shape connection is 30 degrees lagging by HV winding which is delta connected.
Coolant type
- To dissipate the excess heat from the transformers, four types of cooling methods are used.
- Oil Natural Air Natural (ONAN): In this method, the heat produced from the core and winding is shifted to the oil.
- Oil Natural Air Forced (ONAF): Forced air is used to dissipate heat from the dissipating surface.
- Oil Forced Air Forced (OFAF): Oil flow is forced through heat exchangers. Airflow is also forced towards the heat exchanger.
- Oil Forced Water Forced (OFWF): It’s Similar to the OFAF method. The only difference here is, forced water is used to dissipate heat from the dissipating surface.
Also Read: 5 Things to Know Before you Buy a Power Transformer
The other specification of the transformers are as follows:
Dimensions
The dimensions of the Electrical power transformer include two main factors: the height of the window (Hw) and the width of the window (Ww). Two other important entities are the width of the largest stamping (a) and the diameter of the circumscribing circle.
Weight
For any transformer, the weight can be calculated by multiplying the transformer’s capacity in kilovolt amperes (kVA) with a basic impulse insulation level (BIL). The weight of core, winding, and oil for insulation can also be calculated.
Terminals
In a transformer, H terminal denotes high voltage, and the X terminal denotes low voltage. These terminals can either be primary or secondary based on which is the source and which is the load.
Serial Number
The serial number format printed in the transformers is usually used t0 identify information like the year of manufacturing, the month of manufacturing, date of manufacturing, and also the place of manufacturing.
Quality Standards
The International Electrochemical Commission (IEC) and the International organization for standardization (ISO) develop and propose the international standards which are to be followed by the firms in electrical, electronic, and all other related fields.
Applications of Power Transformers
Power transformers are widely used to operate different voltages at high power ratings. The other major role of the Power Transformers is to transmit and distribute electrical energy. In electronic circuits, the Power Transformers are used to accomplish various purposes.
The power generating plants, power distribution centers, and various other industries are largely benefited by using Power Transformers in their manufacturing techniques.
Its application is further extended to textile industries, Pharmaceutics, food manufacturing industries, Hydropower generation, nuclear power generation, thermal power generation, and also in the production of solar energy, wind energy, and biomass generation.