1. What is Inrush Current?

Inrush current is the instantaneous high input current drawn by an electrical device when first turned on. For refrigerator compressors, this occurs when the start capacitor is initially energized.

2. How Does the Calculator Work?

The calculator uses the inrush current equation:

Where:

• \( I_{inrush} \) — Inrush current (amps)
• \( V \) — Applied voltage (volts)
• \( R_{eq} \) — Equivalent resistance (ohms)

Explanation: The equation calculates the peak current that flows when voltage is first applied to a capacitive circuit.

3. Importance of Inrush Current Calculation

Details: Understanding inrush current is crucial for proper sizing of circuit protection devices and preventing nuisance tripping of breakers during compressor startup.

4. Using the Calculator

Tips: Enter the applied voltage in volts and the equivalent circuit resistance in ohms. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is inrush current higher than running current?
A: Inrush current is high because the capacitor initially acts as a short circuit until it charges up to the applied voltage.

Q2: What's a typical inrush current for refrigerator compressors?
A: Typically 5-10 times the normal running current, often in the range of 20-40 amps for household units.

Q3: How can I measure equivalent resistance?
A: Measure DC resistance across the start winding and capacitor when the compressor is off and at room temperature.

Q4: Does temperature affect inrush current?
A: Yes, colder temperatures increase the resistance, which may slightly reduce inrush current.

Q5: How does this relate to capacitor sizing?
A: The start capacitor must be rated to handle the calculated inrush current without failing.