I believe everyone knows that there are many factors that affect the resistance value of a resistor, among which temperature is one of the factors. Temperature has different effects on the resistance value of different substances. The temperature coefficient of resistance is not constant but a value that varies with temperature. As the temperature increases, the temperature coefficient of resistance decreases. Therefore, the temperature coefficient of resistance we refer to is specific to a particular temperature.

The formula for the effect of temperature on resistance:

R2=R1 * (T+t2)/(T+t1) R2=0.26 x (235+(-40))/(235+20)=0.1988 Ω

Calculated value of 80 A

T1---- Winding temperature

T - Temperature constant of resistance (235 for copper wire and 225 for aluminum wire)

T2- Convert temperature (75 ° C or 15 ° C)

R1- Measure resistance value

R2- Convert resistance value

When the temperature range is not large, the resistivity of pure metals increases linearly with temperature, that is, ρ=ρ 0 (1+α t), where ρ and ρ 0 are the resistivity at t ℃ and 0 ℃, respectively, and α is the temperature coefficient of resistance. The alpha value of most metals is approximately 0.4%. Due to the significant linear expansion of α compared to metals (with a temperature increase of 1 ℃, the length of the metal only expands by about 0.001%), when considering the variation of metal resistance with temperature, the changes in length l and cross-sectional area S can be negligible. Therefore, R=R0 (1+α t), where and are the resistances of the metal conductor at t ℃ and 0 ℃, respectively.

When the temperature rises by 1 ℃, the ratio of the increase in conductor resistance to the original resistance is called the temperature coefficient of resistance. Its unit is 1 generation, and its calculation formula is α=(R2-R1)/R1 (t2-- t1). In the formula, R1- the resistance value at temperature t1, Ω; R2- the resistance value at temperature t2, Ω.