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Is your VFD tripping on an Auxiliary Fan Fault ? Learn how to identify failures in external cooling fans and control unit ventilation.   Auxiliary Fan Fault: Protecting the "Brain" of the Drive When we talk about VFD cooling, most people think of the massive fans blowing air through the power heat sink. But many high-performance drives, feature a secondary cooling system. When you see an Auxiliary Fan Fault , the drive is warning you that its "internal climate control" has failed. While the main fan cools the IGBTs, the auxiliary fan is responsible for cooling the Control Unit (CU) , internal capacitors, and localized electronics. If this fan stops, the "brains" of the drive can overheat even if the "muscles" (IGBTs) are still cool. Auxiliary Fan vs. Main Fan: What's the Difference? Main Fan: Large, high-CFM fan located at the base or top of the Power Module. It handles the bulk of the thermal load from the motor current. Auxiliary Fan: Sma...

Is your VFD tripping on a Fan Fault (F0030, F30004, or OH)? Learn how to diagnose seized bearings, blocked vents, and monitoring circuit issues.   Fan Fault: The Small Component That Can Stop a Big Motor It sounds minor—just a small 24V or 230V cooling fan. But if the VFD detects that its internal fan isn't spinning at the correct RPM, it will often trigger an immediate Fan Fault (like F0030 in Siemens or F051 in other brands). The drive does this to prevent a much more expensive IGBT Overtemperature failure. If the air isn't moving, the drive is effectively a ticking time bomb. Why Does a Fan Fault Occur? Modern VFDs don't just "hope" the fan is working; they monitor it using a tachometer signal (a 3rd wire) or by measuring the current draw of the fan motor. 1. Seized or Sticky Bearings In dusty or oily environments, the fan bearings eventually dry out or get clogged. If the fan can’t reach its target RPM within a few seconds of startup, the drive trips. 2....

Is your drive stopping with an "External Fault" (F0006, EPF, or EXT)? Learn how to trace the signal back to your safety circuits, sensors, and PLC logic.   External Fault: When the Drive is Just the Messenger When your VFD trips on an External Fault (often coded as F0085 , EPF0 , EXT , or F0006 ), the drive is usually perfectly healthy. It isn't tripping because of its own internal physics—it's tripping because you told it to. An external fault is a programmed reaction to a signal received on one of the drive's digital inputs. The drive is acting as a "security guard," shutting down the motor because another piece of equipment in the system is screaming for help. Where Does the Signal Come From? The drive is monitoring a specific terminal. If the voltage on that terminal drops (or rises, depending on logic), the drive trips. Common sources include: 1. Motor Thermistors (PTC/KTY) If your motor has internal temperature sensors wired back to the drive'...

Heat is the #1 enemy of Variable Frequency Drives. Learn how proper cooling, airflow, and heat sink maintenance can double the lifespan of your industrial electronics.   Keep Your Cool: Why VFD Thermal Management is Non-Negotiable If you look at the failure reports for industrial drives, one culprit stands above the rest: Heat. A Variable Frequency Drive (VFD) is an incredibly efficient machine, but it isn't perfect. Approximately 2% to 3% of the power passing through a drive is lost as heat. In a 100 HP application, that’s about 2,200 Watts—roughly the same heat as two space heaters running inside your control cabinet. Without a robust cooling strategy, your drive is on a fast track to early retirement. The Anatomy of VFD Cooling VFDs rely on a combination of conduction, convection, and forced air to stay within their operating limits (typically 0°C to 40°C or 50°C). 1. The Heat Sink (The Conductor) The IGBTs and rectifiers are bolted directly to a heavy aluminum block with deep...

Is your VFD tripping on IGBT Overtemperature? Learn the difference between heat sink and junction temps, and how to fix airflow, switching, and loading issues.   Hot Under the Hood: Troubleshooting IGBT Overtemperature In the heart of every Variable Frequency Drive (VFD) are the IGBTs (Insulated-Gate Bipolar Transistors). These components do the heavy lifting, switching high currents at high speeds to control your motor. However, this work generates significant heat. When your drive displays a fault like OH , OH1 , or F0004 , it’s telling you that its internal silicon is approaching its "melting point." Ignoring an IGBT overtemperature fault is the fastest way to turn an expensive VFD into a paperweight. Heat Sink vs. Junction Temperature Most VFDs monitor temperature in two ways: The Heat Sink (NTC/PTC): A sensor mounted on the aluminum cooling block. This is "slow" heat. The Junction (I²t calculation): The drive’s software calculates how hot the actual silicon...

An Output Phase Loss fault can damage your motor and drive. Learn the common causes, how to diagnose it quickly, and prevent future occurrences in your VFD applications.   The Silent Killer: Troubleshooting Output Phase Loss in VFDs You've got your VFD running, the motor seems to be turning, but then suddenly, a fault flashes: Output Phase Loss (or codes like OPL , OLF , or a generic Motor Fault often indicating an imbalance). Unlike an input phase loss where the drive lacks incoming power, an output phase loss means one of the three phases between the drive and the motor has disappeared or significantly weakened. This is a critical fault that can quickly damage your motor and even the VFD itself if not addressed immediately. What Happens During an Output Phase Loss? When a 3-phase motor loses one phase while running, it's called "single phasing." Overheating: The remaining two phases try to carry the entire load, causing a massive surge in current and rapid over...

Is your VFD tripping on DC Link Undervoltage? Learn how to identify input power drops, blown fuses, and internal rectifier issues to keep your motors running.   When the Power Drops: Troubleshooting DC Link Undervoltage While "Overvoltage" is usually caused by the motor pushing back, DC Link Undervoltage (often coded as UV , F0003 , or F30003 ) is usually a "supply side" problem. It means the VFD’s internal DC reservoir has dropped below the level required to safely operate the IGBTs and the motor. When the DC bus voltage sags, the drive can no longer maintain the correct torque, and continuing to run could damage the internal electronics due to high current draw. What is DC Link Undervoltage? The DC Link is the heart of the VFD. It stores energy from the incoming AC line. For a 480V AC drive, the DC link should sit around 650V DC . If that voltage drops below a specific threshold (typically around 400V–450V DC for a 480V unit), the drive will trip to protect it...

Is your VFD tripping on DC Link Overvoltage? Learn about regenerative energy, braking resistors, and how to stabilize your DC bus for peak performance.   High Voltage Alert: Troubleshooting DC Link Overvoltage It’s one of the most common—and frustrating—faults in the world of Variable Frequency Drives (VFDs). You’re running a process perfectly, and then as soon as the machine tries to slow down or stop, the drive trips. The screen reads: DC Link Overvoltage (or codes like F0002 , OV , or OU ). This isn't usually a sign that your drive is "broken." Instead, it’s a sign that the drive has become an accidental battery charger, and the battery (the DC Bus) is full. The "Why": Understanding the DC Bus To understand overvoltage, you have to look at the internal anatomy of the drive. A VFD converts AC to DC, stores it in a "pool" of capacitors (the DC Link), and then converts it back to AC for the motor. The voltage in that DC "pool" is typically 1...

Troubleshooting the F30001 fault on Siemens G120/S120 drives. Learn how to identify if the issue is a motor short, a parameter mismatch, or a failed Power Module.   Siemens F30001: Understanding the Overcurrent Trip If your Siemens SINAMICS display just turned red with F30001 , the drive has hit its absolute hardware current limit. Unlike a standard "Overload" (which is a slow thermal warning), F30001 is an instantaneous trip. The drive has detected a current spike so high that it had to shut down the IGBTs immediately to prevent them from literal physical destruction. Top 3 Causes of F30001 When F30001 strikes, you need to look at three distinct areas: the Load , the Cables , and the Drive . 1. Mechanical "Shock" or Jam If a conveyor jams or a pump tries to start against a closed valve, the motor will attempt to pull massive torque instantly. This surge in current can cross the F30001 threshold before the drive’s software-based current limits can even react. 2. Gr...

Missing a phase on your VFD input? Learn the causes of Input Phase Loss, why it’s dangerous for your DC bus, and how to fix it before your drive fails.   One Leg Down: Troubleshooting Input Phase Loss in VFDs In the world of 3-phase power, balance is everything. When one of those three legs goes missing—a condition known as Input Phase Loss —your VFD starts fighting an uphill battle. While many modern drives can technically run on single-phase power (often with a heavy derating), a drive expecting three phases will quickly throw a fault code like IPL , PF (Phase Fault), or F0003 . Here is what is happening behind the cabinet door and how to get your process back online. What is Actually Happening? A VFD takes incoming AC power and converts it to DC through a component called the Bridge Rectifier . In a healthy 3-phase system, the peaks of each phase overlap, creating a relatively smooth DC voltage. When you lose a phase, the "gaps" between those voltage peaks become much lar...

Understanding why your VFD's IGBTs are overloading is crucial for drive longevity. This post explains common causes, how to interpret fault codes, and practical prevention strategies.   IGBT Overload: The Silent Killer of Your VFD (And How to Stop It) You've heard of motor overloads, but what about an IGBT Overload ? This often-misunderstood fault can silently degrade and eventually destroy your Variable Frequency Drive (VFD) if not addressed promptly. While a short circuit is a sudden, catastrophic event, an IGBT overload is often a cumulative problem, slowly cooking the most critical components of your drive. Let's dive into what an IGBT overload is, why it happens, and how to protect your investment. What Exactly is an IGBT Overload? IGBTs (Insulated-Gate Bipolar Transistors) are the workhorses of your VFD's inverter section. They rapidly switch on and off thousands of times per second to create the variable frequency AC power for your motor. When an IGBT operates, i...

Staring at a Short Circuit fault on your VFD? Don't panic. Here is a practical guide on why it happens, how to find the culprit (Motor vs. Drive), and how to fix it without blowing anything up.   The Dreaded "SC" Trip: Troubleshooting Short Circuit Faults in VFDs If you work with industrial automation, you know the sound. The distinct click of a contactor opening, followed by the winding down of machinery and the sudden, uncomfortable silence of the plant floor. You walk over to the VFD (Variable Frequency Drive), and there it is, flashing in angry red LED letters: SC , F0001 , or OC (Overcurrent). A Short Circuit fault is one of the most aggressive faults a drive can throw. Unlike a simple overload that gives you time to react, a short circuit is instantaneous. It means current has spiked massively—often within microseconds—and the drive has engaged its self-preservation mode to save its expensive internal components. Here is what is actually happening, and more import...

Earth Leakage and VFDs: Is it a Real Fault or Just Noise? You press the start button, and CLICK —the main breaker trips instantly. Or maybe the drive runs for an hour, and then suddenly stops with an "Earth Fault" (EF) or "Ground Fault" (GF) code. Earth Leakage is the most frustrating fault in the book. Why? Because half the time, there is nothing actually broken.   When you deal with standard motors (Direct Online/DOL), an earth fault means one thing: A wire is touching metal, and it’s dangerous. But with VFDs? It’s complicated. VFDs are naturally "leaky" devices. In this guide, I’ll help you figure out if you have a dead motor or just a "nuisance trip," and how to stop it from happening. The Two Types of Earth Faults To fix this, you have to understand which enemy you are fighting. 1. The "Real" Earth Fault (The Dangerous One) This is a physical breakdown of insulation. The Cause: A motor winding has melted and touched the cas...