Question

How do you calculate the transformer winding impedance temperature coefficient?

Answer 1

The transformer winding impedance temperature coefficient (Z% TC) refers to the change in the impedance of a transformer's winding with respect to temperature variations. It is expressed as a percentage change in impedance per degree Celsius (or Fahrenheit) of temperature change.

To calculate the transformer winding impedance temperature coefficient, you will need the following information:

Initial impedance (Z0): The impedance of the transformer winding at a reference temperature (usually at 20°C or 25°C).

Final impedance (Zt): The impedance of the transformer winding at the temperature of interest (measured in °C or °F).

Temperature change (ΔT): The difference between the final temperature (Tt) and the reference temperature (T0). This can be calculated as ΔT = Tt - T0.

The formula to calculate the transformer winding impedance temperature coefficient (Z% TC) is as follows:

Z% TC = [(Zt - Z0) / Z0] / ΔT * 100

Let's break down the steps to calculate the Z% TC:

Step 1: Find the temperature change (ΔT) in degrees Celsius or Fahrenheit.

Step 2: Measure the initial impedance (Z0) of the transformer winding at the reference temperature (T0).

Step 3: Measure the final impedance (Zt) of the transformer winding at the temperature of interest (Tt).

Step 4: Calculate the percentage change in impedance per degree temperature change using the formula:

Z% TC = [(Zt - Z0) / Z0] / ΔT * 100

Example:
Suppose you have a transformer with an initial impedance (Z0) of 8 ohms at 25°C, and at a temperature of 50°C (Tt), the impedance (Zt) measures 8.5 ohms.

Step 1: ΔT = Tt - T0 = 50°C - 25°C = 25°C

Step 2: Z0 = 8 ohms

Step 3: Zt = 8.5 ohms

Step 4: Z% TC = [(8.5 - 8) / 8] / 25 * 100 ≈ 2%

So, the winding impedance of the transformer increases by approximately 2% for every 1°C change in temperature above the reference temperature of 25°C.