1. What Is The Locked Rotor Amps Calculation?

The Locked Rotor Amps (ILR) calculation determines the current drawn by an electric motor when its rotor is locked and unable to rotate. This is an important parameter for motor protection and circuit design.

2. How Does The Calculator Work?

The calculator uses the formula:

Where:

• \( ILR \) — Locked Rotor Amps (amps)
• \( FLA \) — Full Load Amps (amps)
• \( LRA/FLA \) — Locked Rotor Amps to Full Load Amps ratio (unitless)

Explanation: The calculation multiplies the motor's full load current by the LRA/FLA ratio to determine the locked rotor current.

3. Importance Of ILR Calculation

Details: Accurate ILR calculation is crucial for proper sizing of motor starters, circuit breakers, and overload protection devices to prevent damage during motor startup.

4. Using The Calculator

Tips: Enter FLA in amps and LRA/FLA ratio (typically between 5-8 for most motors). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical LRA/FLA ratio for motors?
A: The ratio typically ranges from 5:1 to 8:1 for most AC induction motors, but can vary by motor design and type.

Q2: Why is locked rotor current important?
A: It helps determine the appropriate circuit protection and ensures the motor won't trip breakers during startup while providing adequate overload protection.

Q3: How does motor size affect locked rotor current?
A: Larger motors typically have higher locked rotor currents, requiring heavier-duty starting equipment and circuit protection.

Q4: Can this calculation be used for all motor types?
A: This calculation is primarily for AC induction motors. Other motor types may have different characteristics.

Q5: Where can I find the LRA/FLA ratio for a specific motor?
A: The ratio is typically provided on the motor nameplate or in the manufacturer's specifications.