1. What is DC Motor Resistance?

DC motor resistance is the opposition to current flow in the motor's windings. It's a crucial parameter that affects motor performance, efficiency, and heat generation. Measuring resistance helps in motor selection, troubleshooting, and performance analysis.

2. How Does the Calculator Work?

The calculator uses Ohm's Law:

Where:

• \( R \) — Resistance in ohms (Ω)
• \( V \) — Voltage across the motor in volts (V)
• \( I \) — Current through the motor in amperes (A)

Explanation: The resistance is calculated by dividing the voltage applied to the motor by the current flowing through it. This gives the effective DC resistance of the motor windings.

3. Importance of Resistance Calculation

Details: Knowing motor resistance helps in:

• Predicting power losses (I²R losses)
• Estimating heat generation
• Troubleshooting motor issues
• Designing proper drive circuits
• Calculating starting current

4. Using the Calculator

Tips:

• Measure voltage across motor terminals while running
• Measure current in series with the motor
• For accurate results, motor should be at operating temperature
• Values must be positive and non-zero

5. Frequently Asked Questions (FAQ)

Q1: Why measure resistance when it's specified in datasheets?
A: Actual resistance can vary due to temperature, manufacturing tolerances, and wear. Measuring ensures accurate calculations.

Q2: How does temperature affect resistance?
A: Resistance increases with temperature (for copper, about 0.4% per °C). Hot motors show higher resistance than cold ones.

Q3: Is this the same as impedance?
A: No, this calculates DC resistance only. Impedance includes inductive reactance which varies with frequency.

Q4: Can I use this for AC motors?
A: This gives DC resistance only. For AC motors, you need to consider power factor and reactance for full impedance.

Q5: What's a typical resistance range for small DC motors?
A: Small hobby motors (12V) might be 1-10Ω, while larger industrial motors can be fractions of an ohm.