1. What is Motor Starting Current?

Motor starting current (inrush current) is the temporary surge current that occurs when an electric motor first starts. This current can be 6-8 times higher than the motor's normal full load operating current (FLA) and is crucial for sizing generators and circuit protection.

2. How Does the Calculator Work?

The calculator uses the simple formula:

Where:

• \( FLA \) — Full Load Amps (motor's normal operating current)
• \( Inrush\ Multiplier \) — Typically 6-8 for most AC induction motors

Explanation: The inrush multiplier accounts for the initial current spike when the motor starts, which is needed to overcome inertia and establish magnetic fields.

3. Importance of Starting Current Calculation

Details: Proper calculation ensures your generator can handle motor starts without voltage dips that could damage equipment or cause nuisance trips. Undersized generators may fail to start motors or experience excessive voltage drop.

4. Using the Calculator

Tips:

• Find FLA on motor nameplate or specification sheet
• Use multiplier 6 for easy-starting loads (fans, pumps)
• Use multiplier 8 for hard-starting loads (compressors, air conditioners)
• For precise sizing, consult motor manufacturer data

5. Frequently Asked Questions (FAQ)

Q1: Why is starting current higher than running current?
A: Motors require extra current to overcome inertia, magnetize iron cores, and charge capacitors during startup.

Q2: How long does starting current last?
A: Typically 0.1-3 seconds, depending on motor size and load. Large motors may have longer inrush durations.

Q3: Can I reduce starting current?
A: Yes, using soft starters, variable frequency drives (VFDs), or star-delta starters can reduce inrush current.

Q4: What if I don't know the exact multiplier?
A: Use 7 as a conservative average. For critical applications, consult motor specifications.

Q5: Does this apply to all motor types?
A: This calculator is for typical AC induction motors. Universal motors, DC motors, and synchronous motors have different characteristics.