ماشین حساب مقاومت سیم پیچ موتور

Conductor resistance increases with temperature. To compare measurements taken at different times or conditions, you must normalize to a common reference temperature (typically 25 °C or 75 °C). This is essential for trending and acceptance testing.

Common causes include: shorted turns in one phase, poor connections at terminals or splice joints, different wire lengths (manufacturing issue), corrosion at connection points, or internal winding damage from overheating.

The k constant (234.5 for copper, 225.0 for aluminum) is the inferred zero-resistance temperature — the theoretical temperature at which the material would have zero resistance if the linear relationship held to absolute zero. It simplifies the temperature correction formula.

Ideally, measure at ambient temperature after the motor has been idle long enough to reach thermal equilibrium. Record the exact winding temperature using an RTD or thermocouple, or the ambient temperature if the motor is cold.

It varies enormously: small motors may have 5–50 Ω per phase, while large motors (>500 kW) may have 0.01–0.1 Ω. Always compare phase-to-phase, not against an absolute value.