Troubleshooting Your VFD
Variable Frequency Drives (VFDs) are essential for controlling motor speed and torque in industrial and commercial systems. But like all technology, VFDs can occasionally present problems that disrupt productivity and damage equipment if left unresolved. At Square One Electric Motors & Pumps, we specialize in helping our customers troubleshoot and resolve these challenges with expert guidance and top-tier replacement products from trusted brands like Leeson, Teco-Westinghouse, Toshiba, and Weg.
This blog covers the top five most common VFD issues, how to fix them, and how to prevent them from occurring in the future.
⚡ 1. Overvoltage and Undervoltage Faults
🧾 What’s the Issue?
Overvoltage and undervoltage errors occur when the incoming power supply is either too high or too low. These conditions can result from poor utility power, unbalanced phases, or regenerative energy during motor deceleration.
🔧 Fixes:
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Install line reactors or isolation transformers to stabilize voltage.
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Use dynamic braking resistors for applications with high deceleration demands.
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Check incoming supply voltage and ensure it matches the VFD’s rating.
🛠 Brands in Focus:
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Teco-Westinghouse drives include protective circuits that detect voltage irregularities early.
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Leeson Speedmaster VFDs allow programming of trip limits to match sensitive applications.
🧠 Prevention Tips:
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Maintain steady utility input with surge protection.
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Avoid mismatching VFD voltage ratings with incoming power.
🔄 2. Motor Not Starting or Running Intermittently
🧾 What’s the Issue?
Your VFD powers on, but the motor doesn’t respond or runs inconsistently. This problem is often caused by improper parameter settings, incorrect wiring, or internal component failure.
🔧 Fixes:
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Verify all parameter settings (acceleration, deceleration, frequency, torque limits).
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Check motor leads and control wiring for loose connections.
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Use diagnostic mode if available to identify faults.
🛠 Brands in Focus:
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Century VFDs include self-diagnostics and fault log history.
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Weg drives offer real-time status displays to aid with startup troubleshooting.
🧠 Prevention Tips:
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Double-check parameters during setup.
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Conduct insulation resistance testing before wiring the motor.
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Program soft starts and ramp-ups for smoother engagement.
🔥 3. Overheating
🧾 What’s the Issue?
Overheating in VFDs leads to internal component damage and premature failure. It’s often caused by insufficient ventilation, ambient temperature, or overloading.
🔧 Fixes:
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Ensure proper spacing around the VFD (at least 3–6 inches for airflow).
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Use external fans or cooling enclosures in high-temperature areas.
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Avoid overloading the drive beyond rated output current.
🛠 Brands in Focus:
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Toshiba’s VF-S15 series comes with high-temperature resilience and thermal shutdown protection.
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Leeson’s washdown VFDs are IP65 rated and built to endure heat and environmental challenges.
🧠 Prevention Tips:
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Monitor drive temperature readings periodically.
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Install drives in climate-controlled panels when possible.
⚙️ 4. Nuisance Tripping During Acceleration or Deceleration
🧾 What’s the Issue?
Your VFD trips when speeding up or slowing down, often due to improper tuning or high inertia loads. Sudden demands in torque or current spikes can trigger fault codes.
🔧 Fixes:
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Adjust acceleration/deceleration time to smooth transitions.
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Install dynamic braking resistors or braking choppers.
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Ensure load is balanced and not seizing.
🛠 Brands in Focus:
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Weg CFW100/300 series includes autotuning features to optimize acceleration profiles.
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Century and Leeson drives offer customizable ramp profiles and torque limits.
🧠 Prevention Tips:
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Configure soft stop settings during commissioning.
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Use torque boost features on startup for high-inertia systems.
🧲 5. EMI and Communication Failures
🧾 What’s the Issue?
Electromagnetic Interference (EMI) can affect the VFD’s control signals, causing random faults or erratic behavior, especially in complex systems with PLCs or sensors.
🔧 Fixes:
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Use shielded cables with proper grounding practices.
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Install line filters or EMI suppression devices.
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Separate control wiring from power cabling to avoid noise coupling.
🛠 Brands in Focus:
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Teco-Westinghouse and Toshiba drives are designed with integrated RFI filters.
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Leeson VFDs feature internal EMI suppression for cleaner performance.
🧠 Prevention Tips:
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Follow manufacturer wiring diagrams exactly.
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Keep all control cables under 50 feet where possible.
🧰 VFD Maintenance Tips for Long-Term Reliability
Preventive maintenance can extend the lifespan of your VFD significantly. Here are basic practices to include in your routine:
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Clean filters and heat sinks regularly.
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Keep the drive’s firmware updated if applicable.
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Log operating hours and environmental conditions.
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Use soft brushes or low-pressure air to remove dust from ventilation areas.
❓ Frequently Asked Questions About VFD Troubleshooting
🔌 Can I use any VFD with any motor?
Not quite. While many VFDs are universal in design, you’ll want to make sure your motor is VFD-compatible. Look for terms like “inverter-duty” or “NEMA Premium” on your motor's nameplate. Motors used with VFDs need to withstand heat buildup, voltage spikes, and rapid switching. If you're unsure, our team can help cross-reference and confirm compatibility.
➡️ Learn more: Inverter Motor Selection Guide
🧠 How do I know it’s the VFD and not the motor?
Great question. Common signs that point to a VFD issue rather than the motor include:
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Fault codes on the display
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Motor starts but immediately stops
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Inconsistent speed control
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Audible clicking or buzzing in the drive
Start by checking the error codes, parameter settings, and wiring. If the VFD seems fine, test the motor windings and insulation.
🏭 Industry Applications Where VFD Reliability Is Critical
Understanding where VFDs are most commonly used helps identify signs of stress and failure earlier. Some of the most VFD-dependent industries include:
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HVAC and refrigeration (fans, chillers, compressors)
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Water treatment (pumps, blowers)
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Manufacturing and machining (lathes, grinders, conveyors)
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Agriculture (irrigation systems, barn ventilation)
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Food processing (mixers, transport belts)
In these environments, unplanned downtime caused by VFD failure can lead to lost revenue, product waste, or even equipment damage.
➡️ Don’t miss: How to Understand Different Levels of Horsepower (HP)
🧠 Pro Tips for Installing a New VFD
If you’re upgrading or replacing your VFD, follow these installation tips to avoid problems down the line:
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Use a VFD-rated motor cable with grounding and shielding
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Mount the drive vertically and allow room for airflow (typically 3-6 inches on all sides)
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Use conduit fittings that prevent moisture or dust intrusion
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Program motor nameplate data into the VFD for accurate control
Before powering on, double-check terminal connections, ground continuity, and proper phase rotation.
🛠 Don’t Guess — Let Square One Troubleshoot Your VFD
At Square One Electric Motors & Pumps, we don’t just sell products—we offer expert VFD support, including:
✅ On-site VFD inspection and diagnosis
✅ Same-day replacements from top brands
✅ Support for pump motors, fans, compressors, conveyors, and more
🔗 Shop Replacement VFDs at Square One Electric
If your drive is beyond repair or outdated, we carry new VFDs with updated technology and warranty protection. Our selection includes:
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🌟 Leeson Speedmaster Drives – Versatile for general and washdown duty applications.
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⚙️ Century Drives – Efficient and compact for OEM and retrofit projects.
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🔧 Teco-Westinghouse Drives – Designed for torque-heavy industrial loads.
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🔌 Toshiba Drives – Known for reliability in harsh environments.
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🔩 Weg VFDs – Feature-rich with intuitive interfaces and robust protections.
We specialize in troubleshooting, matching, and upgrading VFD systems. Contact our team to:
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Get help with fault codes and diagnostics
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Receive cross-reference quotes
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Learn which drive is best for your application
Contact us today for personalized support or to order a replacement VFD from Century, Toshiba, Teco-Westinghouse, Leeson, or Weg.