One of the most critical decisions in electrical enclosure design concerns the selection of power supply voltages. In industrial automation, the electrical enclosure is not simply a cabinet: it is the beating heart of the system, distributing power to machinery and ensuring operational continuity.
Factors to consider when selecting the power supply voltage
Why isn’t a single voltage used everywhere? The answer lies in the balance between safety, energy efficiency and component requirements, which varies depending on the operating context.
The choice of power supply voltages inside an electrical enclosure is never arbitrary. It results from a combination of technical, regulatory and application-related factors. The main aspects to consider include:
- Installation environment and application context, which influence both the usable voltage levels and the way power is distributed inside the enclosure, as well as the type of loads to be supplied (motors, drives, automation systems). These factors determine the need for AC power circuits and DC control circuits.
- Safety requirements, including where and how to adopt low voltages and high IP protection ratings in order to reduce risks for operators and comply with applicable standards.
- Reliability and electromagnetic compatibility (EMC) of automation systems, which help minimize disturbances and interference in control signals.
- Target market and available power supply network, which can significantly influence the design choices for the electrical enclosure.
Installation environment and application sector
The installation environment varies depending on the application sector, because the required performance focus changes accordingly, such as in a demanding context like Food & Beverage. The table below summarizes the typical voltage levels used in different industrial contexts and the main operational priorities.
Main voltages used in electrical enclosures
As shown in the examples above, a modern industrial enclosure typically contains two different types of circuits.
1. Power circuits: alternating current (AC)
Power is almost always managed in alternating current in order to drive motors and heavy loads.
- 400V three-phase
The European standard for electric motors and power loads. - 230V single-phase
Typically used for auxiliary services, ventilation systems and service outlets inside the enclosure.
2. Control and auxiliary circuits: direct current (DC)
Operator safety and electronic stability require lower voltage levels.
- 24V DC
This has become the most widely used standard for the so-called “logic” section, which includes the interfaces used to automate processes, monitor machinery and manage production lines through sensors and I/O actuators, typically connected to Programmable Logic Controllers (PLCs).
Using 24V DC significantly reduces the risk of electric shock and minimizes electromagnetic interference. - 110V DC
Still present in some sectors (such as railway or power generation) for long-distance control circuits.
Why has 24V DC become the standard for control logic?
The widespread adoption of 24V DC is mainly driven by three factors:
- Safety (Safety Extra Low Voltage – SELV):
It protects personnel against direct and indirect contact by using non-hazardous voltage levels. - Electronics compatibility:
Modern PLC logic and I/O modules are natively digital and operate more reliably with stabilized DC voltage. - Compact design:
24V components are generally more compact, enabling a reduction in enclosure size.
Electrical enclosures for different markets: the role of voltage and frequency
The voltages used inside an electrical enclosure do not depend only on the installed components, but also on the available power supply network.
While the European industrial standard is 400V at 50Hz, other markets—such as the United States and Canada—commonly operate with 480V or 600V at 60Hz.
This does not simply change the voltage level. It also affects the behavior of components such as transformers, motors and power supplies. In fact, the supply frequency influences electromagnetic parameters and operating performance, with potential effects on motor speed, magnetization currents and thermal dissipation.
For this reason, designing electrical enclosures intended for export requires careful consideration of the technical and regulatory differences between European IEC standards and North American UL/CSA standards, which will be explored in greater detail in upcoming articles.
Thermal management considerations
Another aspect that is often underestimated is the thermal management of electrical enclosures. The presence of transformers, power supplies and conversion devices inevitably introduces energy losses that are dissipated as heat.
When different voltage levels coexist inside the enclosure—such as 400V AC for power circuits and 24V DC for control logic—these conversion devices require adequate heat dissipation.
To ensure the long-term reliability of electronic components, it is therefore essential to correctly evaluate the internal temperature rise (Delta T) according to CEI EN 61439, taking into account the efficiency of conversion stages and the distribution of heat sources.
A proper thermal management strategy helps prevent component derating, improves operational continuity and extends the service life of the entire system.
For this reason, Fandis can support you in designing the most suitable thermal management solution for the operating conditions of your electrical enclosure, thanks to a comprehensive range of products developed to meet different industrial requirements.