1. What is DC Motor Efficiency?

Definition: DC motor efficiency (η) measures how effectively the motor converts electrical power to mechanical power.

Purpose: This calculator helps engineers and hobbyists evaluate motor performance and energy consumption.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \eta \) — Efficiency (percentage)
• \( P_{out} \) — Output mechanical power (watts)
• \( P_{in} \) — Input electrical power (watts)

Output power is calculated as: \( P_{out} = V \times I - I^2 \times R_m \)

Explanation: The calculator accounts for power lost as heat in the motor windings (I²R losses).

3. Importance of Motor Efficiency

Details: Higher efficiency means less energy wasted as heat, longer motor life, and lower operating costs.

4. Using the Calculator

Tips: Enter the motor's supply voltage, current draw, and internal resistance. Typical DC motor resistances range from 0.1Ω to 10Ω.

5. Frequently Asked Questions (FAQ)

Q1: What's a good efficiency for DC motors?
A: Small DC motors typically achieve 50-70% efficiency, while high-quality motors can reach 85-90%.

Q2: Why does efficiency decrease at low loads?
A: Fixed losses (like friction) become significant compared to the reduced output power.

Q3: How do I measure motor resistance?
A: Use a multimeter to measure resistance between motor terminals (disconnected from power).

Q4: Does this account for all losses?
A: No, it only considers resistive losses. Other losses include friction, windage, and magnetic losses.

Q5: Can efficiency exceed 100%?
A: No, that would violate energy conservation. If you see >100%, check your measurements.