1. What is Starting Current?

Starting current (or inrush current) is the instantaneous high current drawn by a motor when it is first turned on. This current can be 6-8 times higher than the full load current (FLA) of the motor.

2. How Does the Calculator Work?

The calculator uses the simple formula:

Where:

• \( FLA \) — Full Load Amps (motor's rated current at full load)
• \( Inrush\ Multiplier \) — Typically 6-8 for most induction motors

Explanation: The inrush current occurs because the motor needs extra current to overcome inertia and establish magnetic fields when starting.

3. Importance of Starting Current Calculation

Details: Knowing starting current is crucial for proper sizing of circuit breakers, fuses, and wiring to prevent nuisance tripping while ensuring adequate protection.

4. Using the Calculator

Tips: Enter the motor's full load current (FLA) from its nameplate and the appropriate inrush multiplier (typically 6-8 unless manufacturer specifies otherwise).

5. Frequently Asked Questions (FAQ)

Q1: Why is starting current higher than running current?
A: At startup, the motor needs to overcome inertia and establish magnetic fields before reaching operating speed, requiring more current.

Q2: How long does starting current last?
A: Typically 0.1-3 seconds, depending on motor size and load inertia.

Q3: Can starting current damage the motor?
A: Normally no, as it's brief. But frequent starts can cause overheating if not properly accounted for in motor selection.

Q4: How can starting current be reduced?
A: Using soft starters, variable frequency drives (VFDs), or star-delta starters can reduce inrush current.

Q5: Does starting current affect power quality?
A: Yes, large motors starting can cause voltage dips that may affect other equipment on the same circuit.