How to Choose the Right Cable for Your VFD – Shielded vs Unshielded
Choosing the correct cable for your Variable Frequency Drive (VFD) is crucial to ensure safe operation, reliable signal integrity, and compliance with EMC regulations. One of the most common questions we get is: Do I really need a shielded cable?
In this guide, we break down when to use shielded vs unshielded VFD cables, what to look for, and how to avoid costly downtime caused by noise interference or cable failures.
🔌 What Makes VFD Cabling Different?
VFDs generate high-frequency switching signals to control motor speed. These signals can cause electromagnetic interference (EMI) and high leakage currents if improper cabling is used.
To manage this, VFD cables must be:
- ✅ Low-capacitance for signal integrity
- ✅ Shielded to prevent EMI from radiating
- ✅ Grounded correctly at both ends
🛡️ Shielded vs Unshielded VFD Cable
| Feature | Shielded VFD Cable | Unshielded Cable |
|---|---|---|
| EMI Protection | ✅ Excellent | ❌ Poor |
| Compliance | ✅ Meets EMC standards | ❌ May fail CE / UKCA tests |
| Application Type | Industrial, critical loads | Basic or non-motor use |
| Cost | 💰 Higher upfront | 💰 Lower cost |
| Recommended for VFD? | ✅ Yes | ❌ Not recommended |
📐 How to Specify a Shielded VFD Cable
When ordering VFD cables, look for:
- 🔹 XLPE or EPR insulation rated 600V–1000V
- 🔹 Symmetrical grounding conductors
- 🔹 Overall copper braid shielding (≥85% coverage)
- 🔹 Class 5 or 6 fine-stranded copper conductors
For long cable runs (>30m), choose a low-capacitance shielded VFD cable to minimise voltage spikes and reflection.
⚠️ What Happens if You Use the Wrong Cable?
- ❌ Nuisance tripping of circuit breakers and RCDs
- ❌ Excessive EMI affecting sensors or PLCs
- ❌ Heat buildup and premature insulation failure
- ❌ Failed EMC compliance or site audits
In short, always use VFD-rated shielded cable for motor leads unless the application is isolated, filtered, and tested.
🔧 Installation Tips
- 🔌 Ground shield at both ends using 360° contact clamps
- 📏 Keep motor cables separate from signal cables
- 🛠️ Use cable glands that maintain shield continuity
For long runs, consider using braking resistors and output reactors to reduce transient stress.
🛒 VFD Cable & Accessories at Drive Outlet Megastore
- ✅ Pre-cut lengths and bulk reels available
- ✅ Shielded, low-capacitance cable in stock
- ✅ Gland kits, EMC clamps, and ferrules
- ✅ Fast shipping across the UK and EU
