VFD Tripping GFCI Breaker: Lenze Drive Solutions & Fixes
Estimated reading time: 12 minutes
Have you ever dealt with your VFD tripping a GFCI breaker unexpectedly? If so, you’re not alone. Variable frequency drives (VFDs) often trip GFCI devices, especially in wet areas or where codes mandate GFCI protection. The result is nuisance tripping—the GFCI breaker shuts off repeatedly, even though your system has no real fault.
In this post, we’ll explain why VFDs trip GFCI breakers. You’ll also learn how to use GFCI devices with Lenze AC Tech drives (and other VFDs) without constant interruptions.
We’ll cover what GFCI devices do and why VFDs can inadvertently trigger them. Such as PWM, leakage currents, and parasitic capacitance. Most importantly, we’ll outline how to troubleshoot and prevent these trips.
By the end, you’ll know the key settings to adjust and cabling practices to follow. You’ll also know when to consider filters or alternate solutions. Our goal is to help you run your VFD with GFCI protection reliably – keeping both your equipment and personnel safe.
What Is a GFCI Device and Why Does It Trip?
Manufacturers design a ground-fault circuit interrupter (GFCI) to protect people from electric shock. It constantly monitors the current leaving and returning to a circuit. If the GFCI senses even a small imbalance—meaning some current leaks to ground—it trips and cuts power within milliseconds.
Standard Class A GFCI devices will trip when they sense around 5–6 mA of leakage. That level is enough to be dangerous to a person. Even though it’s far below the trip threshold of a typical circuit breaker. In contrast, older Class B GFCIs (rarely used now except in certain pool lighting circuits) trip around 20 mA.
GFCIs exist as outlets, breakers, and other devices. Each one disconnects power when current strays to ground. But unfortunately a VFD tripping a GFCI breaker happens for different reasons.
However, this sensitivity means GFCIs can be prone to nuisance tripping in certain scenarios. If a device on the circuit (like a VFD) unintentionally lets a few milliamps leak to ground, the GFCI will assume there’s a fault and shut off the power. This isn’t a flaw in the GFCI; it’s doing its job.
However, in VFD applications we often need to figure out why those few mA are leaking and how to minimize them. Any GFCI that protects a VFD must match the drive’s current rating and type requirements. High-horsepower drives often need a specialized, industrial GFCI designed for heavier loads. Standard residential GFCI outlets or breakers usually handle only 20- to 60-amp circuits.
Why VFDs Trip GFCI Breakers: Leakage Currents and PWM
VFDs by nature generate common-mode currents and electrical noise. The fast switching edges from the drive’s insulated-gate bi-polar transistors (IGBTs) induce tiny currents into anything nearby through parasitic capacitance. For example, every motor cable has capacitance between its conductors and the surrounding earth.
When a VFD outputs high-frequency PWM pulses, some of that energy will flow through the cable’s capacitance to ground. The motor itself also has capacitance between its windings and the stator core (grounded frame), allowing a bit of current to leak to ground. These leakage currents are typically very small (on the order of milliamps), but that’s precisely the range a GFCI is monitoring.
As a result, a perfectly healthy VFD-driven system can appear to a GFCI like a constant “ground fault.” A VFD triggering GFCI breakers is not uncommon, here’s why.
Considerations If The VFD Includes An EMI/RFI Filter
Moreover, if your VFD has an internal EMI/RFI filter (sometimes called a footprint filter), that filter may intentionally shunt high-frequency noise to ground via filter capacitors. That’s great for reducing electromagnetic interference, but it also means a small continuous current to ground – enough to trip a sensitive GFCI. In fact, drives with built-in filters or external EMC filters often include a note that they may trip residual current devices due to the filter’s capacitors. Lenze AC Tech drives (and many other brands) offer optional “low-leakage” filters to address this exact issue.
In short, a VFD naturally leaks a tiny AC current to ground during normal operation. The GFCI interprets that leakage as a dangerous fault. In truth, the current stems from high-frequency switching, not insulation failure. If your VFD trips the GFCI at power-up or motor start, treat it as nuisance leakage. In most cases, no direct short or equipment failure exists.
Now that we understand why it happens, let’s look at how to verify the cause and troubleshoot.
Troubleshooting a VFD Tripping a GFCI Breaker
When faced with a GFCI trip in a VFD system, you should determine whether the trip is due to a real problem (like an actual ground fault) or just high-frequency leakage. Here are some troubleshooting steps:
First, disconnect the motor and run the VFD alone :
Start by running the VFD with no motor connected (if your drive allows it or in “test” mode). If the GFCI still trips with only the drive powered, the problem is likely related to the input side. The drive itself or its input filter may be leaking enough current to cause the trip.
Pay special attention if your VFD is a 120 V single-phase model that boosts to 230 V output (a voltage-doubler design) – these tend to have extra DC bus ripple. This can increase leakage.
If you have an input EMI filter installed, try temporarily removing or bypassing it to see if the nuisance trips stop. A significant portion of leakage often comes from input filters or the drive’s internal filter.
Next, reconnect the motor (using short cables):
If the GFCI does not trip with the motor disconnected, then the combination of VFD + motor + cable is contributing to the leakage. Reconnect the motor and keep the motor cable as short as possible (for testing purposes). Long cables have higher capacitance.
They will leak more current. If the setup trips the GFCI only when the motor is connected, this points to the output side as the source. In other words, the leakage is occurring through the motor and cables. Also check if multiple drives share the same supply. Several VFDs on one GFCI-protected circuit can sum their small leakages into a larger overall imbalance.
Also, inspect grounding and wiring:
Furthermore, make sure the VFD, motor, and cable shields are all properly grounded at both ends. Paradoxically, good grounding doesn’t eliminate leakage – it actually provides a path for these currents to return. However, it ensures those currents take the intended safe path.
Poor grounding can cause higher voltages to build up on equipment, which may increase leakage spikes. Make sure there is no insulation damage or moisture in the motor junction boxes or cable glands. Such issues could cause a real ground fault that trips the GFCI, not just a nuisance trip.
Some GFCI (or RCD) units are designed with an inverse time curve or filtering to be more forgiving of brief surges. If possible, test the VFD on another GFCI breaker – for example, a special-purpose GFCI or a high-quality industrial model – to see if the trip threshold or delay is different.
Finally, test with a different GFCI device if available:
There are even GFCIs made specifically for use with drives (sometimes called “PWM-compatible” RCDs). If the alternate device holds, your original GFCI might simply be too sensitive or fast-acting for the VFD’s inherent leakage. Always use a GFCI device that meets code requirements for your scenario. You cannot use a less sensitive device if the code calls for Class A personnel protection.
Through these steps, you’ll identify whether the trips are inherent leakage or something fixable like a wiring issue. Assuming it’s the former, the next section covers how to prevent these nuisance trips on Lenze AC Tech and other VFDs. There are also other sources that can assist with using GFCI devices on a VFD.
Preventing GFCI Nuisance Tripping on Lenze AC Tech Drives
Once you’ve confirmed that there’s no true ground fault, you can take several measures to reduce the leakage currents or their effect on the GFCI. Lenze AC Tech drives (like the SMVector series) are used in many installations requiring GFCI protection, and Lenze has published guidelines on minimizing nuisance trips. Here are the top solutions:
Lowering the PWM carrier frequency can stop a VFD GFCI trip:
The carrier frequency controls how fast the VFD’s transistors switch on and off (often adjustable from, say, 2 kHz up to 16 kHz). A lower carrier frequency means fewer switching events per second, which reduces high-frequency leakage currents.
It may make the motor whine a bit more (audible noise) and slightly affect smoothness, but it dramatically cuts the risk of GFCI trips. For example, if your drive is set to 10 kHz, try dropping it to 4 kHz or the lowest setting allowed. Many users find that this alone solves the problem.
Set a minimum output frequency to help with a VFD GFCI trip:
Some drives allow programming a “minimum frequency” (for example 15–20 Hz). This is so the motor doesn’t operate at very low speed or DC when starting. Very low frequencies can sometimes produce more imbalance. Once the motor is turning, leakage may stabilize.
This feature is less common, but Lenze notes that avoiding extended operation at 0 Hz (DC hold) can help in GFCI scenarios.
Use the fastest practical acceleration time to reduce VFD GFCI trip likelihood:
When the VFD ramps the motor speed up or down, the changing frequency and any regenerative currents can cause momentary surges. By using a fast acceleration (and deceleration) time, you shorten the duration of these transients.
In essence, you get the motor through the frequency range that might irritate the GFCI more quickly. Just ensure the acceleration isn’t so abrupt that it triggers other faults (like overcurrent or overvoltage) – find a balanced setting for your load.
Minimize motor cable length & use good cable:
As mentioned, long cables add capacitance to the system. Keep motor leads as short as possible. If you must use a long cable, consider adding an output filter or reactor (more on filters shortly). Also, use a properly grounded, shielded cable. A cable shield provides a low-impedance path for high-frequency noise to return to ground.
This actually increases the total leakage current slightly, but it directs the noise away from the GFCI’s sensor. In any case, always ground the motor cable shield at both the drive and motor end.
Check the GFCI class & rating:
Standard Class A GFCIs trip at ~6 mA by design, which leaves very little headroom for VFD leakage. In industrial settings, there are ground-fault protectors for equipment (GFPE) that trip at higher thresholds (for instance, 10–30 mA) and are not intended for personnel protection.
If your application doesn’t specifically require Class A personnel protection, you might use a special GFCI with a higher trip level or a short delay. For example, some manufacturers offer “industrial GFCI” breakers that tolerate brief surges or up to 20–30 mA of leakage. (Always follow electrical codes – NEC only permits Class B (20 mA) in very limited cases, but new UL 943C devices for industrial use now allow up to 20–50 mA trip levels in certain equipment.)
The key is to use the right type of device for the job.
Consider Lenze’s low-leakage filters:
As noted earlier, Lenze AC Tech provides optional low-leakage EMI filters for their drives. These filters limit ground current yet still block noise. If a standard filter on your drive triggers a GFCI trip, swap to a low-leakage version—or remove the filter altogether if EMI isn’t a concern—to see a big improvement.
In some cases, running the drive temporarily without the filter can help confirm whether the filter was the culprit.
Don’t use a “floating” ground on VFDs with VFD GFCI trips:
A myth sometimes heard is that isolating the drive (not connecting it solidly to ground) could stop leakage. This is not recommended – it defeats the purpose of safety grounding and can create dangerous conditions for both people and equipment.
Lenze explicitly advises against running their drives ungrounded (floating input) as a cure for leakage. Always ground your VFD properly per the manual.
Using Filters or Alternate Products if Problems Persist
In most cases, the tweaks above fix the issue. But what if you’ve tried everything and your VFD still keeps tripping the GFCI? At that point, it’s time to consider additional hardware or even a different type of drive.
Alternatively, an output dv/dt filter or a sine wave filter can be placed between the VFD and the motor. These devices filter the PWM output, smoothing the voltage waveform. Consequently, the high-frequency leakage current drops dramatically. This is because the filter removes most of the high-frequency content).
Sine wave filters are very effective at preventing GFCI trips – the motor essentially sees a near-perfect sine wave – but they are also bulky and add cost. For moderate cable lengths, a simpler dv/dt filter (essentially a choke and capacitor network) may be enough to reduce noise to an acceptable level.
Similarly, a last-resort option is to use a drive designed to avoid PWM issues. For example, there are specialized VFDs (such as the NFO “Sinus” drive) that output a pure sinusoidal waveform without high-frequency switching.
Are These VFD GFCI Trip Niche Products Right For You?
These products fall into a niche category and cost more. But manufacturers advertise them to run on GFCI-protected circuits without tripping. If you absolutely need a GFCI and can’t tame standard drives, exploring one of these units may prove worthwhile.
Finally, consider consulting the drive manufacturer’s support. Lenze’s engineers might have model-specific advice or firmware updates to help in GFCI scenarios. (For example, they might recommend certain parameter tweaks or have a list of GFCI brands known to work with their drives.) When in doubt, don’t hesitate to reach out – the manufacturer can often provide insights for tricky interference problems like this.
Having persistent VFD GFCI trip issues?
Reach out to Precision Electric’s team for expert troubleshooting or a free drive evaluation. We can help configure your Lenze drive and suggest the right filters or products to keep your system running safely and smoothly.
Conclusion
In summary, using a VFD with a GFCI breaker can be challenging. However, it’s certainly possible with the right approach. VFD tripping GFCI breakers is usually due to tiny leakage currents from the drive’s normal operation – not because your equipment is faulty. By understanding the cause and implementing the fixes above, you can enjoy both the benefits of speed control and the safety of ground-fault protection.
Always ensure that any solution complies with electrical codes and safety standards. If you’re ever in doubt, involve a professional who has experience with VFDs in GFCI-protected environments. With the tips outlined here, you should be able to significantly reduce or eliminate nuisance trips. Thus, your Lenze AC Tech VFD and its GFCI can finally coexist peacefully – keeping your operations productive and safe from electrical hazards.
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