High Voltage Air Gap Clearance Calculator

Welcome to the High Voltage Air Gap Clearance Calculator! This tool is designed to help you determine the minimum safe clearance distance required between live electrical parts and grounded surfaces or other conductors in high-voltage systems.

By entering your system voltage and considering altitude correction factors, you can quickly find the proper clearance values to ensure electrical safety, compliance with standards, and reduced risk of arcing. Whether you’re an engineer, technician, or a student learning about high-voltage design, this calculator makes the process straightforward.

You can start calculating right away, or continue reading to explore the formula, step-by-step usage, and practical details.

Understanding the Formula

The calculator uses well-established estimation formulas to determine safe clearance distances for high-voltage applications:

General Purpose Estimation Formula
C = 1.25 × (V + 6)

Where:

• C = Clearance in inches
• V = System voltage in kilovolts (kV)

Voltage Conversion:
V (kV) = (System Voltage in Volts) ÷ 1000

Altitude Correction Formula:
Final Clearance = Base Clearance × Altitude Correction Factor

• Final Clearance: The clearance adjusted for altitude
• Base Clearance: Required clearance at or below 2000 m (6562 ft)
• Altitude Correction Factor: About 1% increase for every 100 m above 1000 m (3300 ft)

For PCB Design Applications

• General formula: Spacing (mm) = 0.6 + (Peak Voltage × 0.005)
• For 30V–100V: Spacing (mm) = 0.1 + (Peak Voltage × 0.01)

In simple terms, these formulas show that higher voltages and higher altitudes require larger air gaps because air’s insulating strength decreases under such conditions.

Parameters Explained

C (Clearance):
The minimum required distance between energized and grounded components to avoid breakdown of air insulation.

V (System Voltage):
The operating voltage of the system, converted into kilovolts. This is the main driver of clearance requirements.

Altitude Correction Factor:
At higher altitudes, the air density drops, reducing its insulating strength. This factor compensates for the lower dielectric strength by increasing clearance.

Peak Voltage (for PCB use):
Represents the highest voltage swing in the circuit, often critical in designing safe board spacing.

How to Use the High Voltage Air Gap Clearance Calculator — Step-by-Step Example

Let’s walk through an example:

1. System Voltage: 15,000 volts (15 kV)
2. Base Clearance (Formula):
   C = 1.25 × (15 + 6)
   C = 1.25 × 21 = 26.25 inches
3. Altitude Adjustment: Assume installation at 1500 m altitude.
   • Extra 5% correction (because it’s 500 m above 1000 m).
   • Final Clearance = 26.25 × 1.05 = 27.56 inches

Result: The minimum required clearance is approximately 27.6 inches. This ensures the system operates safely at both the specified voltage and altitude.

Additional Information

Here is a quick reference table for common voltages at sea level:

System Voltage (kV)	Clearance (inches)
5 kV	13.75 in
10 kV	20 in
15 kV	26.25 in
20 kV	32.5 in
30 kV	45 in

This table makes it easier to compare clearance needs at a glance.

FAQs