A step-up transformer is a type of transformer that converts low voltage (LV) and high current from the primary side of the transformer to high voltage (HV) and low current value on the secondary side of the transformer. This is known as the reverse step down transformer.
A transformer is a piece of static electrical device that converts electrical energy (from the primary side winding) into magnetic energy (in the magnetic core of the transformer) and again into electrical energy (to the side of the secondary transformer). A step-up transformer has a wide variety of applications in electrical systems and transmission lines.
The operating frequency and nominal power are approximately equal on the primary and secondary transformer side because the transformer is a very efficient piece of equipment - while the voltage and current values usually vary.
A transformer provides galvanic isolation in the electrical system. Due to these two main features, the transformer is the most important part of the electrical system and provides economical and reliable transmission and distribution of electrical energy.
The transformer can transfer energy in both directions, from HV to LV as well as vice versa. This is why this voltage can act as a step-up or step-down transformer. Both types of transformers have the same design and construction.
Theoretically, we can operate any transformer as a step-up as well as a step-down type. It depends only on the direction of energy flow.
HV winding has a larger number of turns than LV winding. LV winding side wire has more cross-section than HV winding side wire
Because there is a high current flowing towards the LV. Typically, we place LV windings close to the transformer core, and above them, we wound the HV windings.
For a step up transformer, the value of the transformer turns ratio (n) is approximately proportional to the voltage ratio:
Here-
Vp = Primary side voltage
Vs = Secondary side voltage
Np = Primary side Number of turns
Ns = Secondary side Number of turns
The primary side of the step-up transformer (LV side) has a smaller number of turns than the secondary side (HV side).
This means that energy flows from LV to HV. The voltage is stepped up from the primary voltage (input voltage) to the secondary voltage (output voltage).
This equation can be rearranged to the formula for output voltage (ie secondary voltage). This is sometimes referred to as the step up transformer formula:
One can easily determine whether a transformer is a step up or step down transformer by calculating the transformer turns ratio of a transformer.
The most important application of step-up transformer is a generator step-up (GSU) transformer used in all generating plants.
In those transformers, the value of turns ratio is usually higher. The value of the voltage produced in the energy output is increased by a step up transformer and sent for long-distance energy transmission.
The energy produced in the generating plant is at low voltage and high current values. The nominal primary voltage value of a GSU transformer ranges from 6 to 20 kV, depending on the type of generating plant.
The nominal voltage value of the GSU secondary side can be 110 kV, 220 kV, 410 kV, depending on the energy transmission system connected to the GSU secondary side.
The value of current value on the primary GSU side is usually very high and can also be up to 30000A depending on nominal transformer power.
This current value is not practical for energy transmission and has to be reduced due to transmission power loss (R × I ^ 2).
Long-distance energy transmission will not be possible at such a high current. In addition to GSU transformers, galvanic isolation also occurs between the generator and the electrical network.
Step Up Transformer Applications
Small step-up transformers can be used in electronic and electrical devices where voltage increases are required.
But nowadays in modern electronic devices, power electronic circuits are more used due to the small weight and dimensions.
A large power step-up transformer is used as a generating step-up transformer to take the generated electricity to higher voltage levels for efficient transmission of electricity.