Frequency Variator and High Temperatures: A Guide to Prevent Failures Due to Heat
Summer arrives, the thermometer rises, and suddenly that frequency variator that has worked flawlessly all year starts to stop with inexplicable alarms. Does that sound familiar? It's not a coincidence. Heat is the number one stress factor for power electronics and the main cause of production stoppages during the warmer months.
If you're suffering the consequences of high temperatures on your equipment, you've come to the right place. This ultimate guide will explain why this happens and, most importantly, will provide you with strategies and practical solutions to shield your variators from heat.
The Achilles' Heel of Electronics: Why is Heat the Worst Enemy of a Variator?
A frequency variator is a marvel of engineering, but inside it houses extremely sensitive electronic components. IGBT transistors (the heart that modulates power), electrolytic capacitors (which smooth the voltage), and microprocessors are semiconductors that operate optimally within a very specific temperature range.
When the external heat combines with the heat that the variator generates while working, the internal temperature spikes. This excess heat degrades the components, alters their behavior, and ultimately destroys them.
Consequences of Overheating in a Frequency Variator
Heat-related frequency variator issues are not just an annoyance; they are a direct threat to your productivity and the lifespan of your equipment.
Overtemperature Fault Trips
When the variator shows an overtemperature fault and stops, it’s not that it’s broken; on the contrary, it’s a cry for help. It is self-protecting to avoid irreparable damage to its internal components. While it’s a smart safety mechanism, each of these "trips" means an unwanted production stoppage.
Drastic Reduction in Component Lifespan
There is a golden rule in electronics: for every 10°C increase above the design temperature, the lifespan of the components is roughly halved. A variator that could last 10 years, if it constantly operates under excessive heat, might not even last 3. Overheating of the frequency converter is a silent killer.
Loss of Performance and Production Stoppages
An overheated variator may lose its ability to deliver the necessary current, resulting in a loss of torque in the motor. The combination of unexpected stoppages and poor performance translates directly into economic losses, delivery delays, and enormous stress for the maintenance team.
Fundamental Strategies to Combat High Temperatures
Now that we understand the problem, let's move on to the solution. Here is the action plan on three fronts to win the battle against heat.
1. The Key Concept: Derating by Temperature
This is the most important strategy and often the least known.
What is "derating" and why is it mandatory?
"Derating" (or thermal de-rating) is the reduction of a variator's load capacity as the ambient temperature increases above its rated design value (usually 40°C). In simple terms: a 15 kW variator cannot deliver 15 kW if it's at 50°C. Ignoring derating is not an option; it's the number one cause of summer failures.
How to Interpret the Manufacturer's Derating Curves
All serious manufacturers include a derating curve in their technical data sheets. It’s a simple graph:
Horizontal Axis (X): Ambient Temperature.
Vertical Axis (Y): Percentage of the nominal output current that the variator can safely deliver.
You will see that starting from 40°C, the line begins to descend. That’s the power reduction you MUST apply.
Practical Example: Derating Calculation for a 15 kW Motor at 50°C
Let’s imagine a real scenario. You have a 15 kW motor (which consumes about 30A) and the variator will be in an electrical cabinet where the temperature in summer reaches 50°C.
Standard Condition: A typical variator is designed to operate at 100% capacity up to 40°C.
Our Condition: We're at 50°C, which is 10°C above the limit.
Consulting the Technical Data Sheet: The manufacturer indicates a derating of 2% of the nominal current for each degree Celsius above 40°C.
Calculating the VFD Derating:
Temperature excess: 50°C - 40°C = 10°C.
Derating percentage: 10°C * 2%/°C = 20%.
This means that the variator will only be able to deliver 80% (100% - 20%) of its nominal current.
Final Selection: If we choose a 15 kW variator (30A), at 50°C it will only be able to deliver 30A * 80% = 24A. That's not enough for our motor! We need a variator whose capacity at 80% is at least 30A.
Necessary Current / 0.80 = Nominal Current of the New Variator
30A / 0.80 = 37.5A
We need to look for a variator of the next power category, for example, one of 18.5 kW or even 22 kW, that has a nominal current higher than 37.5A.
2. Cooling and Ventilation of the Electrical Cabinet
Derating is vital, but it is useless if the variator is installed in an oven. Cooling the electrical cabinet with a variator is the second pillar.
Proper Design and Spacing Inside the Panel
Heat rises. It is crucial to respect the minimum distances indicated by the manufacturer to allow for natural air convection. As a general rule, leave at least 10-15 cm of free space above and below the variator and avoid placing cable ducts right at the hot air exit.
Forced Ventilation: Fans and Filter Grills
In most cases, natural convection is not enough. A forced ventilation system is needed. This involves installing a fan at the bottom of the control cabinet for VFD to draw in fresh air and a grill with a filter at the top to expel hot air. It is essential to keep these filters clean; a clogged filter is like having no fan.
When is an Air Conditioner Necessary for Cabinets?
Forced ventilation has its limits: it cannot cool the interior of the cabinet below the outside ambient temperature. You will need a cabinet air conditioner if:
The ambient temperature exceeds 40-45°C.
The cabinet is sealed (IP54 or higher) and does not allow ventilation.
There are multiple variators or other heat sources in a small cabinet.
3. Selecting the Right Variator from the Start
Prevention is better than cure. When choosing new equipment, consider these factors.
Pay Attention to the Maximum Operating Temperature
Look for this data in the technical data sheet. Most standard variators operate up to 50°C or 55°C (with derating), but there are models designed for up to 60°C. That difference can be key. It is the operating temperature of the frequency variator that you must respect.
Importance of the IP Protection Rating and Its Impact on Cooling
A high IP rating (like IP66) is excellent for protection against dust and water, but it turns the variator into a sealed box. Heat dissipation becomes much more difficult, and derating is much more severe. For installations within a clean cabinet, an IP20 is more than sufficient and much easier to cool.
Variator Models with Improved Heat Sinks or Liquid Cooling
For truly extreme applications, advanced solutions like variators with oversized heat sinks, "push-through" models (which expose the heat sink to the outside of the cabinet), or even liquid cooling systems are available.
Best Installation and Maintenance Practices
A good piece of equipment, if poorly installed or maintained, will fail just the same.
Strategic Location of the Electrical Cabinet
It seems obvious, but it is a common mistake. Avoid installing the cabinet in places that receive direct sunlight for hours or near other machines that radiate heat, such as ovens or compressors.
Preventive Maintenance Focused on Cooling
The maintenance of variable speed drives in summer should focus on cooling. Create a simple routine:
Monthly: Visual inspection and cleaning of the cabinet grill filters.
Semi-Annual/Annual: With the equipment de-energized, clean the heat sinks and internal fans of the variator with dry, oil-free compressed air. Check that the fans rotate freely.
Typical Mistakes that Cause Overheating of a Variator
Not applying derating when sizing the equipment: The most costly mistake.
Obstructing air inlets and outlets of the cabinet: Leaving flat items, tools, or jackets on top of ventilation grills.
Ignoring the periodic cleaning of filters and heat sinks: A dirty filter negates the cooling system.
Need Help? Professional Sizing and Integration
Calculating derating correctly, designing airflow in a cabinet, and selecting the right equipment can be complex. A sizing error can lead to purchasing the wrong equipment or recurring failures. Having expert support ensures a reliable and optimized solution from day one.
Conclusion: A Reliable Variator is a Well-Cooled Variator
The reliability of a frequency variator in a hot environment is not a matter of luck; it is the result of good engineering. Remember the three keys to success:
Choose Wisely: Always apply derating by temperature.
Install Smartly: Ensure effective cooling of the cabinet.
Maintain Diligently: Keep the paths where the equipment breathes clean.
Don't let heat dictate the pace of your production. With these strategies, your variators will work reliably even on the hottest days of the year.
