1. What is Starting Current of a DC Motor?

Definition: The starting current is the initial current drawn by a DC motor when it's first turned on, before back EMF develops.

Purpose: Understanding starting current helps in selecting proper circuit protection and preventing damage to motor windings.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( I_{start} \) — Starting current (amps)
• \( V \) — Supply voltage (volts)
• \( R_m \) — Motor resistance (ohms)

Explanation: At startup, with no back EMF, the current is limited only by the motor's internal resistance.

3. Importance of Starting Current Calculation

Details: Proper calculation ensures correct fuse/breaker sizing and prevents voltage drops in the power supply system.

4. Using the Calculator

Tips: Enter the supply voltage and motor resistance (typically found in motor specifications). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is starting current higher than running current?
A: Because there's no back EMF at startup to oppose the supply voltage.

Q2: How can I reduce starting current?
A: Use a starter resistor, variable voltage supply, or soft-start circuit.

Q3: What's a typical motor resistance range?
A: Small motors may have 1-10 ohms, while large motors can be 0.01-0.1 ohms.

Q4: Does this apply to AC motors?
A: No, AC motors have different starting characteristics due to inductance.

Q5: What if I don't know the motor resistance?
A: Measure it with an ohmmeter when the motor is off, or consult manufacturer specs.