1. What is 3 Phase Motor Winding Resistance?

The phase resistance of a 3-phase motor winding is the resistance measured between any two phases of the motor. It's an important parameter for motor performance analysis and fault detection.

2. How Does the Calculator Work?

The calculator uses the balanced 3-phase resistance formula:

Where:

• \( R_{phase} \) — Phase resistance (ohms)
• \( V \) — Line voltage (volts)
• \( I \) — Line current (amperes)

Explanation: The formula calculates the equivalent resistance per phase in a balanced 3-phase system by accounting for the √3 relationship between line and phase quantities.

3. Importance of Phase Resistance Calculation

Details: Measuring winding resistance helps identify shorted turns, open circuits, or other winding faults. It's also used for calculating copper losses and efficiency.

4. Using the Calculator

Tips: Enter line-to-line voltage in volts and line current in amperes. All values must be positive numbers. For accurate results, measurements should be taken with the motor at rest.

5. Frequently Asked Questions (FAQ)

Q1: Why is √3 used in the formula?
A: In balanced 3-phase systems, the relationship between line and phase quantities involves a √3 factor due to the 120° phase separation.

Q2: What are typical resistance values for motor windings?
A: Resistance varies by motor size and design, but typically ranges from fractions of an ohm to several ohms for larger motors.

Q3: When should resistance measurements be taken?
A: Best performed when the motor is cold, as resistance increases with temperature. Always disconnect power before measuring.

Q4: Does this work for unbalanced systems?
A: This formula is for balanced systems only. Unbalanced systems require individual phase measurements.

Q5: How does temperature affect resistance?
A: Resistance increases with temperature. For copper windings, resistance increases about 0.4% per °C rise in temperature.