open frame vs enclosed power supply

Your application needs the correct supply of voltage, current, and frequency to work. However, electrical energy from the source may not have these in the appropriate proportions. This is where power supply comes in. A power supply is a device that converts the source energy into usable power needed to power your end equipment. It supplies AC-DC power to your application and can either be a separate device or come preinstalled in the electrical load.

Power supplies are essential because, by regulating the input energy, they also prevent its attendant current and voltage surges from reaching the electrical load. This goes a long way in mitigating electrical hazards and faults in the end device. They can also store energy to temporarily power the electrical load in case of an emergency power outage.

There are different classifications of power supplies. However, on the basis of frame format, they are of two types: open frame and enclosed power supply. Through our open frame vs closed frame power supply comparison, this article will break down these two types of power supply and their differences. You will also learn how to pick the right type for your application.

What is an Open Frame Power Supply?

Open frame power supplies, as their name implies, are power supplies that feature open casing. They do not come with protective housing to cover the internal components. Essentially, an open frame power supply has a populated PCB without any covering.

The application then houses it and protects it from the elements of weather and other external interferences.

What is an Enclosed Power Supply?

An enclosed power supply has the same parts as an open power supply—internal components that are fixed to a base PCB. However, in addition to this, an enclosed power supply has a casing that covers its internal components.

The material for this enclosure is usually metallic but some enclosed power supplies come in non-metallic casing. A closed frame power supply provides a higher degree of safety for you by preventing shocks. The enclosure also protects the internal components of the device from interference from external factors such as electromagnetic noises and the elements. We will discuss these in more detail in the latter sections of this article.

Open Frame vs Enclosed Power Supply: What are the Key Differences?

The most obvious observation in any open frame vs enclosed power supply comparison is the construction. While an open frame power supply has the electronic components simply attached to the printed circuit board (PCB) without an enclosure, an enclosed power supply has a protective material—which can be plastic or metal—covering the components.

This difference in design has wide-ranging effects on each type of power supply and confers on them the characteristics that distinguish them. Below are some of them;


One downside to open frame power supplies is that they are prone to short-circuiting and expose you to electrical shocks. To mitigate this, you must adhere to creepage and clearance distances when incorporating power supply into your application. This implies the provision of a safe distance for insulation between the power supply and the equipment chassis on all sides of the enclosure. This distance is usually 10mm for industrial equipment and 15mm for medical power supplies.

Another important safety consideration for creepage and clearance distances is the ground connection. The ground connection plays a delicate role in maintaining the safety of the entire system and cannot be overlooked. The distance between the earthed metal and the power supply depends not just on the type of equipment but also on its system class. For Class I systems, this distance should be kept at a minimum of 3mm for industrial power supplies and 4mm for medical supplies. This is also true for Class II systems with insulating enclosures. However, Class II systems with a metal chassis will require larger clearance and creepage distances.

On the contrary, closed frame power supply usually has all these accounted for by the manufacturers when enclosing it.

Thermal Build-Up

The components of open frame power supplies are open to the air; hence they can get cooled by free air convection. This helps them to stem internal heat build-up. Nevertheless, other factors relating to the application, such as space surrounding the power supply and heat from other components of the application, may encourage heat build-up in the power supply.

Enclosed power supplies, on the other hand, are prone to heat build-up because the metal exterior tends to trap heat, causing the internal components to heat up quickly. Besides convection cooling, forced air cooling (fan) is a common way of ensuring that the power supply does not exceed its maximum temperature rating.

Electromagnetic Compatibility

Because an open frame power supply is not enclosed, it is susceptible to electromagnetic interference. This can be further worsened by the multiple ground connections a power supply requires for safety purposes. All but one of these are output common-node capacitor ground connections and they affect the EMC performance of the power supply.

Therefore, these connections must be made to reduce electromagnetic interference to the barest minimum. A common practice is to connect the output ground connection points if the end equipment uses plastic or any other non-conductive chassis. End equipment with a metallic chassis does not, however, require this precaution.

Contrarily, electromagnetic interference is less likely in an enclosed power supply, thanks to its protective casing. Nevertheless, electromagnetic compatibility control technology could also be employed to further keep interference levels to the barest minimum. This technology is usually sufficient enough to suppress electronic noises while also protecting the equipment from external noises in either power supply type.


Because of its open construction, an open-frame power supply is more accessible than a closed-frame power supply. In the event of a fault, it is more straightforward to troubleshoot an open frame vs closed frame power supply. This is because a closed-frame power supply requires its enclosure to be opened first in order to check the problem.

Size and Weight

Size and weight cannot be ignored in an open-frame vs closed-frame power supply comparison. Open-frame power supplies are generally lightweight and small because they are designed to utilize small spaces in their end applications. Enclosed-frame power supplies can be standalone devices and space considerations are not prioritized for them as much as open-frame power supplies. Hence, the average closed-frame power supply is heavier and bulkier than the average open-frame power supply.

Open Frame vs Closed Frame Power Supply: Which is Right for Your Application?

In choosing the right power supply for your application, you should consider factors such as your application’s power output requirement, operational safety requirements, and electromagnetic compatibility, among others.

Operational Safety

As said earlier, an open-frame power supply exposes application operators, servicing, and repair workers to electrical shocks because of its open nature. However, a physical barrier around it would prevent this. Hence, an enclosed power supply would be better if you are big on safety and want to save yourself from the stress of open-frame safety considerations during installation.

Electromagnetic Compatibility

The open design of an open-frame power supply makes the components not only unprotected from the elements but also susceptible to electromagnetic interference. On the other hand, the enclosure of a closed-frame power supply protects it from electromagnetic interference and other noises. Hence, it is preferred in industries that require high-precision results, such as the medical industry.

Thermal Management Factors

Heat has a direct effect on the efficiency of power supplies—the higher the heat, the lower the efficiency. A power supply can malfunction if the heat goes above its maximum temperature rating. In fact, many power supply failures result from overheating.

Open frame power supply is less likely to be affected by heat build-up. However, the chassis of an enclosed power supply traps heat that can be detrimental to the internal components. Open frame wins in this category of open frame vs enclosed power supply comparison. If you cannot afford unnecessary, corrective maintenance-related application downtime, then an open-frame power supply would be ideal for you.

Looking for Quality Electric Components You Can Count on?

Now that you know about open frame vs enclosed power supply, you might also want to know where to get the best one for your application. Bravo Electric is one of the most reliable suppliers of quality electric components from reputable manufacturers globally. Our AC DC power supply collection is vast—including 12 volt DC power supply, 24 volt DC power supply, and 48 volt DC power supply. Our engineers are always on hand to assist you in getting the most suitable product for your application. We can also help with your custom power supply projects. Our delivery is prompt—same-day delivery is even available in some instances.

Final Thoughts on Open Frame vs Closed Frame Power Supplies

To conclude our open-frame vs closed-frame power supply discussion, power supplies are vital to the smooth running of your application. Your application specs and requirements will guide you in deciding the type that you want. In choosing a power supply, you cannot afford to compromise on quality and application suitability. The wrong product, over time, will cost you a lot in maintenance, repair costs, and application inefficiency. This is what Bravo Electric is here to prevent. Why not reach out to us to order your quality open and closed-frame power supplies now?