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3 Phase Transformer Size Formula:
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The 3-phase transformer size calculation determines the required kilovolt-ampere (kVA) rating of a transformer based on voltage and current values in a three-phase electrical system. This is essential for proper electrical system design and equipment selection.
The calculator uses the 3-phase transformer formula:
Where:
Explanation: The formula calculates the apparent power in a three-phase system, accounting for the phase relationship between voltage and current.
Details: Proper transformer sizing is crucial for electrical system efficiency, safety, and reliability. Undersized transformers can overheat and fail, while oversized transformers are inefficient and costly.
Tips: Enter voltage in volts and current in amps. Both values must be positive numbers. The calculator will compute the required transformer size in kVA.
Q1: Why is √3 used in the formula?
A: √3 (approximately 1.732) accounts for the phase difference in three-phase systems, where voltage and current are 120 degrees out of phase with each other.
Q2: What's the difference between kVA and kW?
A: kVA measures apparent power (voltage × current), while kW measures real power. The ratio between them is the power factor (cos φ).
Q3: Should I add a safety margin to the calculated kVA?
A: Yes, it's common practice to add a 15-25% safety margin to account for future load increases and transformer aging.
Q4: Does this formula work for both delta and wye configurations?
A: Yes, the formula applies to both delta and wye configurations when using line-to-line voltage and line current.
Q5: How does temperature affect transformer sizing?
A: Transformers have reduced capacity at higher ambient temperatures. Manufacturers provide derating factors for different temperature conditions.