Drives at High Temperatures
Over the years Northern Industrial has assisted in the installation of drives in some of the world's toughest environments. With customers based around the globe, drives serviced and repaired by our engineers contend with the world’s most extreme environments on a daily basis.
Whether or not the drive is installed in a hot climate, it’s normal for drives to be situated near a heat source. For example in the metals industry hot temperatures are a day-to-day requirement. Yet, hot temperatures pose risks to the functionality and the ageing process of a drive.
For every AC drive, minimum and maximum operating temperatures are listed within the specifications tables. For most AC drives the maximum operating temperature will be 40 °C, to put this temperature into context this is the average July temperature for Kuwait City and below the record temperature of 45.9 ℃ reached in France in June 2019. So, in reality we often need to consider how our AC drive will cope when the mercury tops this 40℃ limit.
What impact does high temperature have on an AC drive?
Firstly, it is worth considering the impact of high temperatures on drives. Even before it hits maximum output drives can be affected by high temperature. When drives are stored in direct sunlight capacitors are vulnerable to damage. High temperatures will accelerate the natural aging process within the electrolytic capacitors as the electrolyte dries out. A solution for this would be a drive reliant on thin film capacitors which are less likely to fail.
How to ensure a drive remains functional at high temperatures
When a drive operates at high temperature, the drive compensates for the stress incurred by using built-in derating algorithms to limit the output current to the motor. This functionality is designed to protect both the drive and its motor. For unusual periods of high temperature this preservatory functionality could be enough to ensure your drive remains operational. However, if you know your drive will be subject to this stress on a regular basis then it’s worth considering a drive with a higher rating. With a higher rating the output can be high enough to ensure the motor remains functional.
Consideration should also be given to switching pattern and switching frequency. Switching pattern and switching frequency selected for the insulated-gate bipolar transistors (IGBTs) can become unreliable as the temperature rises. A drive’s ability to switch frequency is impeded and load cycles are also affected.
It is also worth noting that a drive’s lifespan is generally considered to reduce by 50% for every 10 °C the drive exceeds the operating temperature. So, not only will functionality be sacrificed at high temperatures but reliability will also be lost. To avoid costly repairs and replacements it really is worth choosing the right drive for your application.
How to choose the right drive for high temperatures
Manufacturers such as Danfoss can help you plan for high temperatures. They offer a large range of drives capable of operating at temperatures of up to 50 °C, at full load without derating. They even offer a drive which can operate at 60°C, the VACON® 100 X. This drive combines large front cooling fins and oversized cooling fans, to fully maximise its high temperature capabilities.
It really is worth thinking about how your drive can be cooled, especially if the application demands functionality above 60°C. An option could be to use a drive with a cold plate designed to dissipate heat from the drive.
Although sometimes a cold plate simply isn’t enough. In these instances external cooling should be considered. When a drive is located within an electrical room or cabinet then air conditioning can be a solution. However, costs can quickly mount when using an air conditioning solution, especially when the drive is the only device which requires cooling.
Further cooling capacity can be gained through flange-mounted installation. This method of installation allows hot air to be expelled through a back-channel. Most of the control electronics are housed within the panel, the heatsink protrudes so it can be cooled by external air flow, or by a separate air duct. This method vastly improves efficiency and maintenance costs.
Under normal circumstances when air pressure allows for thermal energy to dissipate this is a great solution. However, at high altitudes air struggles to conduct heat from the drive. This is when it’s worth considering using a liquid cooled drive. The VACON NXP Liquid Cooled drive from Danfoss offers fantastic power density due to the efficiency of liquid cooling. This drive only dissipates 5% of its heat loss through the air, meaning there’s no need to build a separate room to enclose the drive. Liquid cooled drives are also exceptionally quiet, at the most they’ll just have small circulation fans, so additional noise impact is significantly reduced.
There’s a lot to consider when installing a drive, especially when it needs to withstand high temperatures. If you need any help or advice on how to install your drive or the best drive for you then get in touch with Northern Industrial.