Why Overvoltage, Overcurrent, and Short Circuit Protection are Important in Power Supplies

Why Overvoltage, Overcurrent, and Short Circuit Protection are Important in Power Supplies Blog Post Image
Reliable industrial power supplies are essential not only for delivering power but also for protecting both themselves and their loads against damage from overvoltage, overcurrent, and short circuit conditions. In this article, we’ll explore the importance of these protection mechanisms and highlight the advanced features of RECOM’s RACPRO1 series of DIN rail power supplies.

Overvoltage Protection

In the context of a power supply, “overvoltage” refers to a situation where the output voltage exceeds its specified rated value; that is, the supply starts to deliver a higher voltage than intended. There are several reasons why a PSU may experience overvoltage, including external voltage surges or spikes, or components failing inside the PSU. If the overvoltage is not corrected, it could result in damage to the PSU, damage to the load, or both. In a worst-case scenario, overvoltage may create a fire hazard.

Industrial power supplies incorporate an overvoltage protection (OVP) circuit, which automatically shuts down the output when it detects an overvoltage condition. In high-end industrial power supplies, the OVP circuit typically includes two feedback loops. In this setup, if the primary feedback regulation fails, the backup overvoltage lockout will disable the power supply.

Overcurrent and Short Circuit Protection

In the context of a power supply, the term “overcurrent” refers to a situation where the current flowing out of the power supply exceeds its maximum rated limit; in other words, the supply begins to deliver more current than intended. There are two main causes of overcurrent. The first occurs when the load attempts to draw more current than the supply is designed to provide. This is often a temporary issue, such as a heavy load requiring extra power during startup. To mitigate this, most industrial AC-to-DC power supplies can supply short-term overcurrent, typically ranging from 120% to 140% for a few seconds.

The second cause of overcurrent is a short circuit on the power supply’s output. This could result from several factors, including damaged wires, loose connections between wires, exposed conductors touching, or a fault in the load that inadvertently creates a path for current to flow with very low resistance. If an overcurrent condition persists, it may cause overheating of the power supply components, leading to potential damage to both the power supply and the load.

Industrial power supplies are equipped with an overcurrent protection (OCP) feature that automatically reduces or cuts off the output current once it reaches a preset limit, preventing damage to the device. High-end industrial power supplies often offer adjustable overcurrent protection modes, including hiccup and tripping (foldback) modes. In this context, foldback protection refers to a method where the output voltage lowers alongside the current, reducing the overall power delivered to the load. In the case of hiccup protection, when an overcurrent condition occurs, the power supply temporarily shuts off its output, then restarts, repeating this cycle until the overload is cleared. This "hiccupping" allows the system to attempt recovery from the overcurrent condition.
RACPRO1 DIN rail power supply: T240 (left), T480 (middle), and T960 (right)
Fig. 1: The RACPRO1 DIN rail power supply family: T240 (left), T480 (middle), and T960 (right)
The members of this family feature industry-leading overvoltage, overcurrent, and short-circuit protection features, including the following:

  • They offer over 35V of return voltage immunity, making the output resistant to back-feeding loads such as decelerating motors and inductors.
  • They can supply an additional 120% power at 45°C, with a 150% power boost for up to 5 seconds, thereby saving costs for extra power supplies and providing high-power starting capability for heavy loads.
  • They support easy fuse tripping, ensuring the secure activation of external fuses and circuit breakers on the output to protect both the power supply and the load.

RECOM's RACPRO1 DIN rail power supplies also feature adjustable overcurrent protection modes, including hiccup and foldback modes. This allows users to select their overcurrent protection method based on specific application needs. With power-boost capabilities and fuse-tripping support, the RACPRO1 series establishes a new standard for industrial PSUs.

Additional Resources

The RECOM AC/DC, DC/DC, and EMC Book of Knowledge provides an extensive collection of insights and best practices necessary to implement successful AC/DC power supply designs. Chapter 12 discusses strategies to reduce housekeeping power consumption along with some measuring techniques.

Also, RECOM’s Energy Efficiency in AC/DC Power Supplies: Quick Guide to the Essentials blog offers a helpful introduction to Ecodesign regulations, which are a set of standards and guidelines established by governments or regulatory bodies to ensure that products are designed to minimize their environmental impact throughout their life cycles. These regulations primarily focus on improving energy efficiency and promoting sustainability by reducing waste, emissions, and resource consumption.

The RACPRO1 webpage provides more information about this exciting new DIN-rail mounted power supply family.
Applications
  Series
1 AC/DC, 240 W, Single Output, DIN-Rail RACPRO1-T240 Series
Focus New
  • Slim Design (43mm) with 25° Push-In connectors
  • Fast tool-less mounting and demounting
  • Active Inrush Current Limitation
  • 2-phase AC operation 2x350V to 2x575V
2 AC/DC, 480 W, Single Output, DIN-Rail RACPRO1-T480 Series
Focus New
  • Slim Design (52mm) with 25° Push-In connectors
  • Fast tool-less mounting and demounting
  • PFC >0.9 and Active Inrush Current Limitation
  • DC-Input Range 430V to 815V/850V 10s
3 AC/DC, 960 W, Single Output, DIN-Rail RACPRO1-T960 Series
Focus New
  • Slim Design (80mm) with 25° Push-In connectors
  • Fast tool-less mounting and demounting
  • PFC >0.9 and Active Inrush Current Limitation
  • DC-Input Range 430V to 815V/850V 10s