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If the phase resistance of the winding is R phase and the line resistance is R line, the calculation of the line resistance can be calculated according to the series-parallel principle of the resistor.

**●Line
resistance by phase resistance**

When the motor winding is star-connected, the schematic is shown in Figure 1, and the R line = 2R phase.

When the motor winding is at the corner, the schematic is shown in Figure 2, and the R line = 2R phase / 3.

**●The
phase resistance is converted by line resistance**

The formula for calculating the line resistance from the phase resistance can be mathematically converted under different connections.

When the motor winding is star-connected, the schematic is shown in Figure 1, R phase = 0.5R line

When the motor winding is angled, the schematic is shown in Figure 2, and the R phase = 1.5R line.

**●
Conversion of resistance values at different temperatures**

Generally, the DC resistance of a metal conductor has a fixed relationship with its temperature. This relationship is expressed as:

R1=R2×(K+t1)/(K+t2).........(1)

Where: R1 - DC resistance (Ω) at a temperature of t1 ° C;

R2——DC resistance (Ω) at a temperature of t2°C;

K - constant (reciprocal of the temperature coefficient of the conductor resistance at 0 ° C), for copper windings, K = 235, for aluminum windings, K = 225.

**●
Resistance standard under different test conditions**

In the type test report, the specific resistance value is given according to the different insulation grade of the motor, such as the resistance of the B-class insulated motor at 75 °C, while the F-class insulated motor is the resistance at 95 °C, and the H-class insulated motor is Resistance at 105 °C. In the inspection test evaluation standard, it is customary to give the resistance at 20 ° C. When the temperature deviates, it can be converted according to the formula (1).

JYR 10S/20S **transformer winding resistance tester**,Yn/D(Y) three phase winding measurement.