What is the formula of the resistance of the winding is calculated at 75°C?

The resistance of a winding or conductor at any temperature can be calculated if the resistance at a reference temperature is known. When dealing with electrical windings, the change in resistance due to temperature can be calculated using the formula:

[ R_T = R_{ref} times [1 + alpha(T – T_{ref})] ]

Where:

– (R_T) is the resistance at the target temperature (the resistance you’re trying to find),

– (R_{ref}) is the resistance at the reference temperature (usually given or measured),

– (alpha) is the temperature coefficient of resistance for the material of the winding (different for copper, aluminum, etc.),

– (T) is the target temperature in degrees Celsius (75°C in your question),

– (T_{ref}) is the reference temperature in degrees Celsius (usually 20°C if not otherwise specified).

The temperature coefficient of resistance ((alpha)) is typically 0.00392°C(^{-1}) for copper and 0.00381°C(^{-1}) for aluminum, assuming the reference temperature is 20°C. These coefficients can vary slightly depending on the source, so it’s important to use the correct value for your specific application.

For example, if you’re calculating the resistance at 75°C for a copper winding that has a resistance of 100 ohms at 20°C, the formula would work as follows (using (alpha = 0