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Transformer Impedance Formula:
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Transformer impedance calculation converts the percentage impedance value (Z%) to actual ohmic impedance (Z) using the transformer's rated voltage and apparent power. This is essential for power system analysis and fault current calculations.
The calculator uses the impedance conversion formula:
Where:
Explanation: The formula converts the percentage impedance (which is normalized to the transformer's base impedance) to the actual impedance value in ohms.
Details: Accurate impedance calculation is crucial for determining fault currents, voltage regulation, and system stability in electrical power systems. It helps in proper protection coordination and equipment sizing.
Tips: Enter impedance percentage (Z%), rated voltage (V), and apparent power (S). All values must be positive numbers. The result will be the impedance in ohms (Ω).
Q1: What is percentage impedance (Z%)?
A: Percentage impedance is the voltage required to circulate full-load current through one winding when another winding is short-circuited, expressed as a percentage of the rated voltage.
Q2: Why is impedance important in transformers?
A: Impedance affects voltage regulation, fault current levels, and parallel operation of transformers. It also influences system stability and protection settings.
Q3: What are typical Z% values for transformers?
A: Typical values range from 3% to 10% for distribution transformers, and up to 15% or more for special applications. The value depends on transformer design and application.
Q4: How does impedance affect fault currents?
A: Higher impedance transformers limit fault currents, while lower impedance transformers allow higher fault currents. This affects protective device selection and coordination.
Q5: Can this formula be used for three-phase transformers?
A: Yes, the formula applies to both single-phase and three-phase transformers. For three-phase transformers, use line-to-line voltage and three-phase apparent power.