Power Supplies and Harsh EnvironmentsMay 13, 2021 by Aaron Yarnell, CUI Inc.
In this article, we will discuss power supplies in harsh environments, the challenges, solutions, and available in-market products.
For power supplies, harsh environments involve far more issues than just humidity and dust. Rugged yet efficient internal power supplies that meet the demands of industrial environments are needed to address these applications.
Power Supplies and Harsh Environments
A host of applications require an internal harsh environment power supply, starting with those found in a general industrial environment, including inverters for industrial control. Such power supplies use intelligent manufacturing, including CNC machines, welding machines, and robotic arms.
Harsh environment power supplies are suited for smart transportation, including mission-critical systems such as electronic traffic control and traffic LED displays. Environmental protection systems also demand harsh environment power supplies, including monitoring systems for air, water, soil quality, garbage sorting, and classification. Other applications for harsh environment power supplies include products ranging from automated storage cabinets (e.g., Amazon drop boxes or hospital medicine cabinets), charging piles, and battery management systems.
As the demand for such systems and equipment grows, so does the need for reliable, efficient power supplies to perform in harsh environments.
Challenges for Power Supplies in Harsh Environments
Internal power supplies for the applications and systems described above face their own set of challenges. They may be subject to significant voltage variations, extreme power surges, and lightning strikes that could cause severe damage to the power supply and the equipment it powers. Harsh EMI, especially in industrial environments, is also a serious concern (where avoiding electromagnetic interference can be difficult due to the many sources).
Often, the power supplies must also be able to start up efficiently and effectively at low temperatures and face wide variations in operating temperature and the challenges posed by high humidity. For its integration in the system it powers, the power supply itself also has cooling issues that must be addressed but limited space available to do so.
Figure 1. Harsh environmental factors for power supplies
Characteristics of Rugged Power Supplies
Rugged power supplies must have a wide input voltage range and excellent immunity to over-voltage and surges to function safely and reliably.
Keep in mind that when the input voltage rating is exceeded, the results can include component and system damage or failures and compromise the effectiveness of EMI filters. A wide input voltage range and tough transient protection circuits allow the power supply to accommodate variations due to issues such as power surges and brownouts.
Surges are most severe at the distribution panel and power supplies must be rated with the proper overvoltage category for their location within the system, see Figure 2.
Figure 2. Overvoltage categories
They also need to support a wide operating temperature range and be resistant to high humidity levels. When a power supply’s maximum operating temperature is surpassed, it can quickly lead to changes in performance, component failure, and reliability. Humidity can lead to condensation—and water is both conductive and corrosive, which is why a rugged environment power supply must be able to perform reliably and predictable even in the presence of elevated humidity levels.
Additionally, modern applications demand a compact size with a low profile, which must be encased in a durable material that supports cooling by free air convection. This is, of course, in addition to meeting the requirements of applicable standards and possessing appropriate certifications.
CUI VGS 100W Harsh Environment Power Supplies
The CUI VGS 100W product series are single output chassis-mount internal AC-DC power supplies that provide up to 110 W output. They are specifically designed for harsh environment industrial applications and housed within a low-profile, rugged metal case.
The CUI VGS 100W power supplies have a wide input range of 85 ~ 305 VAC (120 ~ 431 Vdc) and have been rated for input over-voltage category III with stronger than normal surge immunity. As category III, the power supplies are designed to be used with protection and control panels, sockets, and equipment to monitor electrical values. They also provide short-circuit over-current protection, and output over-voltage protection.
The industrial AC-DC power supplies are compact at 129 x 97mm with a very low 30mm profile. As noted earlier, they are housed in a tough galvanized Aluminum 1100 metal case that supports convection cooling. They also have a wide operating temperature range of -30°C to 70°C and a maximum operating humidity of 90%. As an added option, these power supplies can also be supplied with a conformal coating that protects the internal circuits from damage due to moisture, dust, and other contaminants,
The CUI VGS 100W power supplies (Figure 3) are UL/EN/IEC 62368 certified and designed to meet IEC/EN 61558, IEC/EN 60335 system requirements, and the CISPR/EN55032 Class B radiated/conducted emissions requirements. They are also IEC safety Class I with a layer of basic insulation and a grounded conductive chassis. If the basic insulation fails, any conductor carrying a hazardous voltage will be grounded by the chassis to prevent contact with the high voltage.
Figure 3. CUI’s VGS-100W Series AC/DC power supply
For reducing standby power usage in industrial applications, this line of power supplies is able to adapt with no-load power consumption ranging between 0.3 and 0.5 W. Depending on the model; efficiency ranges from 85.5 to 90.5% measured at 230 VAC.
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