To choose a three-phase transformer, first determine the voltage levels on the primary and secondary sides to ensure compatibility with your electrical system. Evaluate the power rating needed, which should match or exceed the load requirements. Consider the physical size of the transformer, cooling requirements, and any specific features or certifications required for your application.

To calculate the transformer, you need to determine the voltage ratings and power requirements.

Calculate the apparent power (in kVA) by multiplying the primary side voltage and current and dividing by the transformer efficiency if necessary. Make sure the transformer meets voltage and current specifications and can handle the expected load.

To know which transformer to choose, identify the specific voltage, current and power requirements of your application. Choose between different types of transformers based on their features, such as step-up, step-down, or isolation.

Verify that the transformer ratings match the operational requirements and constraints of your system.

Criteria for choosing a transformer include voltage rating, power rating (kVA), efficiency and cooling requirements. Consider the type of transformer needed (e.g., three-phase, autotransformer) and any additional features such as load regulation or protection mechanisms.

Make sure the transformer fits your installation space and meets safety and operational standards.

To calculate the apparent power of a three-phase transformer, use the formula: Apparent Power (S) = √3 × Voltage (V) × Current (I). This calculation provides the power rating in volt-amps (VA) or kilovolt-amps (kVA), which helps select a transformer with appropriate power capacity for the application.