EMI Risk

📐 Calculation Steps

1

Identify sources

Frequency: 50/60Hz, PWM (2-20kHz), or RF

VFDs, power cables, switchgear are common sources.

2

Check separation

Per IEC 61936-1 and 61000-5-2

Physical distance between power and signal cables.

3

Evaluate shielding

SE = 20*log10(E_inc/E_trans)

Cable shield type and termination.

🧮 Formula

EMI Risk Score

Risk = (log(f)*P)/(d*10^(SE/20))

Proportional to frequency and power, inverse to separation and shielding.

Symbol	Variable	Unit
f	Source frequency	Hz
d	Cable separation	m
SE	Shielding effectiveness	dB
P	Power level	kW

📋 Worked Example: VFD-to-Sensor Interference

Result:

🔍 Result Interpretation

✅ Risk < 1

✅ 1-5

✅ 5-20

✅ > 20

🔥 Guidance

Critical signal interference Risk > 20

Signals in high-risk zone may cause equipment malfunction.

💡 Engineering Recommendations

🔧

Power cables parallel to signal >10m

Increase separation to 500mm minimum or install steel divider.

Steel divider between cable trays gives >20dB additional attenuation.

⚡ Quick Facts

2-20kHz typical

VFD PWM frequency

300mm power to signal (IEC 61000-5-2)

Minimum separation

30-40dB better than pigtail

360deg bonding

🔬 Engineering Insight

"The most common EMI mistake is pigtail shield termination. A 1-inch pigtail can reduce shielding effectiveness from >60dB to <10dB at 10MHz. Always use 360-degree bonded glands for critical signal cables."

📜 Standards & References

IEC 61000-5-2 — IEC

Installation and mitigation guidelines for EMC.

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❓ Frequently Asked Questions

🔧 Related Calculators

→

Cable Size Calculator

📖 Related Knowledge

→ EMC Installation Guide

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📥 Input Parameters

📤 Results