DC Motor Current Calculator

DC Motor Current Formula:

\[ I = \frac{HP \times 746}{V \times \eta} \]

Current (I): amps

Definition: This calculator estimates the current draw of a DC motor based on its horsepower rating, operating voltage, and efficiency.

Purpose: It helps electrical engineers and technicians properly size power supplies and wiring for DC motor applications.

The calculator uses the formula:

\[ I = \frac{HP \times 746}{V \times \eta} \]

Where:

Explanation: The formula converts horsepower to watts (746W = 1HP), then divides by voltage and efficiency to find current.

Details: Proper current estimation ensures correct wire sizing, circuit breaker selection, and power supply capacity for safe motor operation.

Tips: Enter the motor horsepower, operating voltage, and efficiency (default 0.9 for 90% efficient motors). All values must be > 0.

Q1: Why 746 in the formula?
A: 746 watts equals 1 horsepower, converting mechanical power to electrical power.

Q2: What's a typical motor efficiency?
A: Small DC motors are typically 70-85% efficient, while larger motors can reach 90-95%.

Q3: Does this include startup current?
A: No, DC motors can draw 2-3 times more current at startup. Consider this for circuit protection.

Q4: How accurate is this calculation?
A: It provides a good estimate, but actual current may vary based on load and operating conditions.

Q5: Can I use this for AC motors?
A: No, AC motor current calculation requires power factor consideration. Use an AC motor calculator instead.