1. What is DC Motor Resistance?

DC motor resistance is the opposition to current flow in the motor's windings, calculated using Ohm's Law (R = V/I). It's a key parameter for understanding motor performance, efficiency, and thermal characteristics.

2. How Does the Calculator Work?

The calculator uses Ohm's Law:

Where:

• \( R \) — Resistance in ohms (Ω)
• \( V \) — Voltage across the motor terminals (Volts)
• \( I \) — Current through the motor (Amperes)

Explanation: The resistance is directly proportional to voltage and inversely proportional to current. This calculation gives the DC resistance of the motor windings.

3. Importance of Resistance Calculation

Details: Knowing the motor's resistance helps in:

• Determining power losses (I²R losses)
• Calculating starting current
• Estimating motor heating
• Troubleshooting motor issues
• Designing appropriate drive circuits

4. Using the Calculator

Tips:

• Measure voltage when motor is running at steady state
• Measure current simultaneously with voltage
• For locked-rotor resistance, measure with rotor prevented from turning
• Values must be positive and non-zero

5. Frequently Asked Questions (FAQ)

Q1: Is this the same as impedance?
A: No, this calculates DC resistance only. Impedance includes inductive reactance which varies with frequency.

Q2: Why measure resistance?
A: Resistance helps predict motor performance, efficiency, and thermal characteristics under load.

Q3: How does temperature affect resistance?
A: Resistance increases with temperature (about 0.4% per °C for copper windings).

Q4: What's a typical resistance range?
A: Small motors may be 1-10Ω, larger motors fractions of an ohm. Exact values depend on motor design.

Q5: Can I use this for AC motors?
A: This gives DC resistance only. AC motors require impedance calculations that include inductance.