1. What is Motor Starter Size?

Motor starter size refers to the current rating required for a motor starter to safely handle the electrical load of a motor. It's typically calculated as 125% of the motor's full load amps (FLA) to provide a safety margin.

2. How Does the Calculator Work?

The calculator uses the standard starter sizing formula:

Where:

• FLA — Full Load Amps (the current a motor draws at full load)
• 1.25 — Safety factor (125% of FLA)

Explanation: The 25% safety margin accounts for potential current spikes, voltage fluctuations, and provides headroom for reliable operation.

3. Importance of Proper Starter Sizing

Details: Correct starter sizing is crucial for motor protection, preventing overheating, ensuring reliable operation, and complying with electrical codes (NEC Article 430).

4. Using the Calculator

Tips: Enter the motor's full load amps (FLA) as specified on the motor nameplate. The value must be greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: Why is the 125% factor used?
A: The 25% margin accounts for inrush current, voltage variations, and provides a safety buffer for reliable operation.

Q2: Where can I find the FLA for my motor?
A: FLA is typically listed on the motor nameplate or in the manufacturer's specifications. It can also be calculated from motor power ratings.

Q3: Are there exceptions to the 125% rule?
A: Yes, some applications like hermetic refrigerant motors may require different sizing factors. Always consult applicable codes.

Q4: What about motors with special starting characteristics?
A: Motors with high inertia loads or frequent starts may require larger starters. Consult an engineer for special cases.

Q5: Does this apply to both manual and magnetic starters?
A: Yes, the sizing principle applies to both types, though magnetic starters offer additional protection features.