Enter your Calculation Type, Primary Turns (Np), Secondary Turns (Ns), and either Primary or Secondary Impedance to find the Referred Impedance — plus your Turn Ratio and Impedance Transformation Ratio — for any Transformer Impedance problem.
Referred Impedance
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Turn Ratio (Np:Ns)
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Impedance Transformation Ratio
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Turn Ratio (Ns:Np)
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Transformer impedance is the opposition to current flow in a transformer circuit, consisting of resistance and reactance components. It affects voltage regulation, short-circuit current, and power transfer efficiency.
Transformer impedance is crucial for determining voltage regulation, fault current levels, parallel operation capability, and overall system stability. It directly impacts transformer performance and protection system design.
Higher impedance reduces short-circuit current but increases voltage regulation. Lower impedance improves voltage regulation but increases fault current. The optimal impedance depends on specific application requirements.
Z impedance (percentage impedance) is the impedance of a transformer expressed as a percentage of its rated impedance. It's typically measured during short-circuit tests and ranges from 4% to 10% for power transformers.
Referred impedance is calculated using the turn ratio squared. When referring from secondary to primary: Z_referred = Z_secondary × (Np/Ns)². When referring from primary to secondary: Z_referred = Z_primary × (Ns/Np)².
The impedance transformation ratio is the square of the turn ratio. If the turn ratio is N, then the impedance ratio is N². This relationship is fundamental in transformer impedance calculations.
Yes, transformer impedance is measured through short-circuit tests where one winding is short-circuited and reduced voltage is applied to the other winding until rated current flows. The impedance is calculated from the applied voltage and current.