Field Resistance Calculator

Field Resistance Formula:

\[ R_f = \frac{T_c \times \rho \times L_{mt}}{A_f} \]

Turns per Coil (Tc):

turns

Resistivity (ρ):

Ω·m

Length of Mean Turn (Lmt):

Area of Field Conductor (Af):

m²

Field Resistance (Rf):

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1. What is Field Resistance?

Field resistance refers to the electrical resistance of the field winding or field coil in a machine such as a generator or motor. It is a crucial parameter in electrical machine design that affects the performance and efficiency of the machine.

2. How Does the Calculator Work?

The calculator uses the Field Resistance formula:

\[ R_f = \frac{T_c \times \rho \times L_{mt}}{A_f} \]

Where:

\( R_f \) — Field Resistance (Ω)
\( T_c \) — Turns per Coil (turns)
\( \rho \) — Resistivity (Ω·m)
\( L_{mt} \) — Length of Mean Turn (m)
\( A_f \) — Area of Field Conductor (m²)

Explanation: The formula calculates the resistance of field winding based on the number of turns, material resistivity, length per turn, and conductor cross-sectional area.

3. Importance of Field Resistance Calculation

Details: Accurate field resistance calculation is essential for determining the voltage drop across field windings, calculating power losses, designing efficient electrical machines, and ensuring proper machine operation under various load conditions.

4. Using the Calculator

Tips: Enter turns per coil as a positive integer, resistivity in Ω·m, length of mean turn in meters, and area of field conductor in square meters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What factors affect field resistance?
A: Field resistance is affected by the number of turns, conductor material resistivity, length of winding, and cross-sectional area of the conductor.

Q2: Why is field resistance important in machine design?
A: Field resistance determines the voltage drop across field windings, affects excitation requirements, and influences the overall efficiency and thermal performance of electrical machines.

Q3: How does temperature affect field resistance?
A: Resistance increases with temperature due to the positive temperature coefficient of most conductor materials. The relationship is given by R = R₀[1 + α(T - T₀)] where α is the temperature coefficient.

Q4: What are typical resistivity values for common conductor materials?
A: Copper: 1.68×10⁻⁸ Ω·m, Aluminum: 2.82×10⁻⁸ Ω·m, Silver: 1.59×10⁻⁸ Ω·m at 20°C.

Q5: How is length of mean turn calculated?
A: Length of mean turn is calculated using empirical formula Lₘₜ = 2L + 2.5τₚ + 0.06kᵥ + 0.2 where L is the gross length of the stator and τₚ is pole pitch in meter.