Drive cooling concepts fit for extreme ambient conditions
In this blog post the author shares thoughts on how to keep the power electronics cool (but not too cold) in extreme environmental conditions. While there may be multiple technical solutions, the focus is on smart drive cooling concepts that suit for wide range of ambient conditions, both cold and warm.
Introduction
This post was inspired by the lasting heat wave in Europe in the summer of 2026. As our company is Europe based, we get the experience first hand. Hot weather, little to no rain, dried nature, risk of wildfires and so on.
In my career as a drive design engineer I have seen and worked on tens of projects with end user sites worldwide. There are regions that are historically known to have very warm climate, for example Middle East countries, many regions in Africa or Australia. Europe traditionally has milder climate although there are of course differences between southern Europe and Scandinavia. The summer of this year (2026) is showing us that even Europe can get pretty hot. And it is not just exception that happens 2-3 days in a year. The heat waves this year continue, with little breaks, from mid of May until present (beginning of August). The impact of the lasting hot weather is visible on human, nature and equipment. It ranges from discomfort and health problems over wildfires up to ramping down the power of nuclear power stations.
The extreme weather also affects industrial power electronics and drives. And that is the point we are going to address.
Environmental factors
The environmental conditions shall be defined in the project technical specification. They include aspects such as:
- Minimum and maximum ambient temperature (indoor and outdoor)
- Site elevation (above sea level)
- Relative humidity (range)
- Solar irradiation
- Rainfall (e.g. mm/year)
- Wind load
- Snow load
- Pollution degree
Past practice and future trends regarding ambient conditions
The IEC standards typically consider design ambient temperatures as follows:
- Yearly average temperature 20°C
- Monthly average temperature 30°C
- Daily maximum temperature 40°C
That is a usual approach for transformers (IEC 60076) and similarly for MV switchgear (IEC 62271) and so on.
Applying those ambient temperatures for the design of equipment is a common practice. Until recently, one could consider it as conservative rating for European installations. 40°C in central Europe? The equipment may never see it and if, then only for a few hours per day within one extremely hot week in the whole year. Well, this year shows us a reality that can be quite different. As of today (August 8) the statistics is following:
- 4 heat waves
- May 24 – May 30
- June 17 – July 2
- July 2 – July 25
- July 28 – present
- Total 59 hot days
In 2026, we already count 59 officially recognized hot days and the season is not over yet. That is not a short period anymore. The equipment shall be designed to withstand such conditions and operate in a reliable way.
Extreme environmental conditions
Hot ambient is one extreme. Very cold ambient is another extreme. Handling them may require a special design. Wide range of temperatures poses another challenge. Let’s look at some examples:
Middle East countries (United Arab Emirates, Kuwait, Qatar, Saudi Arabia etc) have a very hot climate and the maximum ambient temperature for design is typically 50°C or 55°C. However, minimum ambient temperature is no issue.
Northern Sweden may be very cold in winter with ambient temperatures down to -30°C or -40°C. However, maximum ambient temperatures are mild.
Countries with continental climate, such as areas in Canada or Kazakhstan, have large seasonal differences with minimum temperatures down to -40°C and maximum temperatures up to +40°C.
Each case is specific. Designing equipment for hot non-freezing environment is somewhat different than designing equipment for ambient that is moderately warm but can also get very cold.
Impact of extreme ambient conditions
Extreme ambient conditions may impact the variable frequency drives in following ways:
- Power derating
- The loading of the equipment must be reduced to avoid overheating and equipment failure
- Reduced lifetime / accelerated aging
- When exposed to excessive temperatures, the equipment ages faster
- Higher auxiliary consumption
- Assuming that we keep the equipment within its design temperatures, a stronger cooling is required. That comes with increased auxiliary (own) consumption.
- Poor utilization of equipment
- Designing the equipment for “extremes” leads to lower utilization (e.g. adding glycol due to low minimum ambient temperature while operating during hot days)
Smart drive cooling concepts fit for extreme conditions
What is the definition of a smart cooling concept? In author’s view the system shall tackle following points:
♦ Relatively simple solution – engineers find beauty in simplicity
♦ Economical solution – because money matters, of course
♦ Robust and reliable – design supporting redundancy and high availability
♦ Low maintenance – you don’t want to shut down the entire drive system (even scheduled downtime) just because of maintenance on your cooling system
♦ Suitable for wide range of ambient conditions – the system can cope with both hot and cold ambient
♦ Compact design – footprint is often premium
Why efficient cooling matters
The motivators for efficient cooling system are:
♥ Optimal utilization of power hardware
♥ Minimization of own consumption
♥ Reduced OPEX
♥ Reduced total footprint
⇒ Learn more about smart cooling concepts
In our on-demand webinar you learn practical tips for design of drive cooling that keeps your VFD at optimal temperature even at challenging ambient temperatures (hot and cold).
References
[1] How to choose a medium voltage VFD: Cooling type, MB Drive Services, May 2019, available online, https://mb-drive-services.com/choose-mv-vfd-cooling/
[2] What shall be considered for recooling of electric rooms, MB Drive Services, September 2022, available online, https://mb-drive-services.com/what-shall-be-considered-for-recooling-of-electric-rooms/
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