The reliability of power supplies in industrial applications is not just a matter of convenience but a critical necessity. The smooth operation of power supplies ensures the uninterrupted functioning of industrial processes, many of which are integral to safety, productivity, and economic efficiency. In this blog, we shed light on an often-overlooked aspect that significantly impacts power supply functionality – transient overvoltages. 

The industrial environment is harsh and unforgiving. Power supplies in such settings are subjected to extreme conditions, including high temperatures, dust, moisture, and electrical noise. These conditions demand a level of robustness and reliability that goes beyond the ordinary. 

Furthermore, power supplies must meet the requirements of the European EMC Directive 2014/30/EU, among others, to be placed on the market in the EU. This requirement underscores the importance of electromagnetic compatibility, stipulating requirements for a certain degree of tolerance (robustness) to the impacts of other systems.

A key element here is the power supply’s immunity (robustness) to transient overvoltages (also known as surge voltages) from the supply network. Understanding and mitigating these transient phenomena are essential for enhancing the reliability and longevity of power supplies in industrial settings.

Understanding transient overvoltages

Transient overvoltages are temporary, high-amplitude events that can significantly exceed the normal operating voltage of power supply systems. Causes of transient overvoltages include lightning strikes, power outages, and the abrupt switching off of large loads like electric motors or heavy switchgear. 

These events can induce voltage spikes in the power supply, potentially leading to operational disruptions, equipment damage, or even catastrophic failures. The transient nature of these overvoltages makes them particularly harmful, as they can compromise the reliability of power supplies without immediate detection.

To safeguard against the detrimental effects of transient overvoltages, the corresponding harmonised testing standard IEC/EN 61000-4-5 ‘Test and measurement procedures – Surge immunity test’ specifies the testing methodology and minimum requirements for evaluating the surge immunity of electrical and electronic equipment, including power supplies. This standard delineates the criteria for both symmetrical and asymmetrical immunity, ensuring that equipment is tested against both types of surge events. 

Symmetrical immunity pertains to surges occurring in the same phase across conductors, while asymmetrical immunity addresses surges between conductors and the ground. In a power supply, symmetrical immunity (L/N to L) of at least 1kV and an asymmetrical immunity (L/N to PE) of 2kV are required for the input side (also the primary side). Adherence to this standard is crucial for certifying the resilience of power supplies against transient overvoltages.

The asymmetrical interference immunity describes the resistance of the protective insulation. If the protective insulation is damaged by a transient overvoltage, the power supply can no longer be operated safely or will not resume operation at all. To minimise this risk of failure, the protective insulation of the TDK-Lambda DRB3 series of 120/240/480/960W 3-phase DIN-rail power supplies has a double design enhancing reliability by providing redundancy and additional protection. In particular, it can withstand asymmetrical overvoltages (L/N to PE) of up to 4kV, which is twice as high as the standard requires (Figure 1).

Figure 1: The TDK-Lambda DRB3 series can withstand asymmetrical overvoltages (L/N to PE) of up to 4kV – twice as high as the standard require

Integrating gas arresters for optimal protection

One effective strategy for mitigating the effects of transient overvoltages (L/N to PE) involves the integration of gas arresters into power supply designs – in addition to the standardised requirements. Gas arresters, or gas discharge tubes (GDTs), considerably reduce the danger of power supply failure by dissipating the energy of a transient overvoltage in a controlled manner to a safe level using the protective earth, thereby protecting the safety insulation (Figure 2). The DRB3 series illustrates this approach by incorporating a gas discharge tube that limits surge voltages to a range between 1kV and 2kV, irrespective of the surge’s severity.

Figure 2: The integrated gas discharge tube (GDT) reduces the danger of power supply failure by protecting the safety insulation 

The integration of gas arresters into power supply designs represents a prudent and effective strategy for enhancing the reliability of power supplies in industrial applications. By mitigating the effects of transient overvoltages, gas arresters ensure the continuous and safe operation of industrial processes. While the initial investment in such protective measures may be higher, the long-term savings in operating and maintenance costs, coupled with increased operational reliability, justify this upfront cost.

The adherence to standards such as the European EMC Directive and IEC/EN 61000-4-5, coupled with the strategic incorporation of protective devices like gas arresters, underscores TDK-Lambda’s commitment to operational excellence and reliability. As we continue to navigate the complexities of modern industrial environments, the emphasis on safeguarding power supplies against transient overvoltages will remain paramount.

To explore the options available for improving immunity to transient overvoltages through the DRB3 series of power supplies, please visit: https://www.emea.lambda.tdk.com/uk/products/drb-3-phase-series