Selecting Power Supplies for Harsh Industrial Applications and Hazardous Locations

Industrial systems in harsh and potentially explosive environments, including production lines, robotics, energy infrastructure, refineries, and semiconductor manufacturing, are increasingly automated. System designers need power supplies that meet requirements for high peak power and back-power immunity, while supporting reliability, durability, safety, high power density, efficiency, and complex regulatory compliance.

This article discusses the challenges facing designers of power systems for harsh automation applications. It then introduces DIN rail power supplies from TRACO Power and shows how they can help designers address these challenges.

Industrial power challenges

Manufacturing production lines, renewable energy systems, distribution warehouses, and chemical processing facilities are all applications that expose electronic devices and systems to industrial environments. The electronics may be exposed to temperature extremes, humidity, mechanical shock, electromagnetic interference (EMI), vibration, dust, chemical exposure, and explosive atmospheres. As electronics are widely used for power, control, and monitoring, they must be designed for accuracy, precision, reliability, and safety across all these applications.

Power supplies are particularly critical. At the core of industrial electronics, they provide regulated power from both AC and DC sources, and their output must meet the baseline energy needs of the connected machines with a sufficient safety margin. For instance, electromechanical systems such as motors, pumps, and motion-controlled drives require high peak currents at startup, which the power source must supply. Protection from overvoltage, overcurrent, and overtemperature is also generally required.

Power supplies must exhibit good voltage regulation under load or line variations and guarantee high efficiency. This is especially important for power supplies mounted in compact enclosures, where low efficiency results in excessive heat buildup.

The power supply form factor is also important. It must be able to fit into machines or control cabinets where space is limited. Also, industrial applications require the ability to quickly replace defective devices, so the physical device should be mounted for easy removal and replacement. Critically, power supplies must be certified for safety and electromagnetic compatibility (EMC).

Hazardous locations

Hazardous locations (HazLoc) are a special area of certification. The National Electrical Code (NEC) defines hazardous locations as areas where fire or explosion hazards may exist due to flammable gases or vapors, flammable liquids, combustible dust, or ignitable fibers or flyings. Power supplies and other electronics must be specifically certified for operation in HazLoc environments.

Underwriters Laboratories Inc. (UL) and Appareils destinés à être utilisés en Atmosphères Explosibles (ATEX) (equipment for use in explosion-hazardous areas) establish the standards for testing HazLoc components. These certifications confirm that the minimum relevant safety standards have been met for the device to be used in designated hazardous environments.

Certification considers two factors: the types of volatile substances and the likelihood of their presence. The types of potentially explosive materials determine the certification class. Class 1 includes flammable vapors and gases; Class 2 covers combustible dust, such as flour; and Class 3 is for ignitable fibers and flyings (small flammable particles, such as fabric).

The likelihood of volatile substances being present determines the division classification. Division 1 covers environments where hazardous materials are normally present. Division 2 covers environments where hazardous materials are not usually present but could be under certain conditions.

Power supplies for HazLoc applications

TRACO Power's DIN rail TIB-EX series of high-efficiency power supplies (Figure 1) is designed for use in harsh environments and hazardous locations. DIN rail is a metal rail widely used to mount industrial control equipment in equipment racks or cabinets. These power supplies also feature a side-mounting option that provides a lower profile for flat-panel mounting. The series is safety qualified to UL HazLoc Class 1 Division 2 (C1D2) and ATEX (EN60079-0, EN60079-7, and EN60079-15) and is EMC certified.

Figure 1: The TIB-EX series of DIN rail power supplies is HazLoc C1D2 qualified, EMC certified, and has power ratings of 80 W, 120 W, 240 W, and 480 W. (Image source: TRACO Power)

HazLoc C1D2 power supplies are designed to operate safely in areas where flammable gases or vapors are normally contained but may escape under unusual conditions, such as leaks, equipment malfunctions, or ventilation system failures.

The most important attribute of C1D2 equipment is that it must not be an ignition source under both normal and unexpected operating conditions. The equipment is designed not to release electrical or thermal energy sufficient to ignite a volatile atmosphere. As such, it cannot produce arcs or sparks during normal operation, and its physical packaging limits the rate at which the volatile substance can enter.

In addition to their HazLoc certifications, these convection-cooled power supplies feature a high efficiency of 88 to 95% (model dependent) and can operate over a temperature range of -40°C to +60°C (full load). Available with power ratings of 80 W, 120 W, 240 W, and 480 W at output voltages of 12 V, 24 V, or 48 V, they operate from line voltages of 85 V_AC to 264 V_AC at 50/60 Hz.

The TIB-EX series is ideal for industrial environments, with a full set of operating protections, including output overvoltage and short-circuit protection. On the input side, they protect against power line voltage sag, defined as a drop in voltage below 90% of nominal, but not a complete interruption. The typical duration is from 3 to 10 cycles or 50 ms to 167 ms. This series complies with the SEMI F47 sag-immunity specification.

The TIB-EX supplies can also tolerate short-term power overloads, sustaining their output for up to 4 s at 150% overload. This is ideal for designs that use stepper motors, solenoids, or actuators that draw high current when initially connected.

Another common occurrence in industrial settings is back power, where loads, such as inductors and decelerating motors, can feed voltage back to the power supply. The TIB-EX series provides an important back power immunity feature that helps prevent shutdowns or malfunctions under these loads.

Switched-mode power supplies (SMPSs) must initially charge their input capacitors, which can lead to large inrush currents when the supply is first connected to the line. Most SMPSs, such as the TIB-EX series, use an inrush current limiter to control it. The inrush current rating of these supplies is 30 A for a 230 V_AC input and 15 A for a 115 VAC input.

All models report output status via a DC-OK contact closure and DC-OK LEDs located on both the front and side panels.

The 80 W TIB 080-112EX AC/DC DIN rail power supply (Figure 2) has a rated output voltage of 12 V and a maximum current of 6.7 A. It is housed in a compact form factor measuring 3.71" × 1.26" × 4.50"

Figure 2: The TIB 080-112EX is a 12 V, 80 W DIN rail HazLoc-rated power supply. (Image source: TRACO Power)

The TIB 080-112EX uses a flyback switching regulator with a switching frequency between 60 kHz and 75 kHz. The 12 V output is adjustable from 11.8 V_DC to 15.0 V_DC, the input voltage regulation is 0.1%, due to line variations across the rated input voltage range, and the load regulation is 0.5% for a load variation of 10 to 90% of the rated load. It operates at 90% efficiency and has a mean time between failures (MTBF) of 1,950,000 hours (hr), per IEC 61709.

The TIB 120-124EX (Figure 3) is an example of a 120 W DIN rail power supply. It has a 24 V, 5 A output rating and measures 4.5" × 4.89" × 1.42".

Figure 3: The TIB 120-124EX is a 24 V, 120 W power supply in a 4.5" × 4.89" × 1.42" package. (Image source: TRACO Power)

The TIB 120-124EX uses a half-bridge inductor-capacitor-capacitor (LCC) topology with a switching frequency of 70 to 100 kHz. It also features active power factor correction.

This power supply’s nominal 24 V output is adjustable from 23.5 V to 28 V, and it has a rated efficiency of 94%. Its MTBF is 1,450,000 hr.

Designers needing higher power can choose the TIB 240-148EX (Figure 4), a 240 W power supply model with a nominal output voltage of 48 V and a maximum output current of 5 A. It comes in a larger form factor, measuring 4.5" × 4.89" × 1.89".

Figure 4: The TIB 240-148EX is a 240 W DIN rail power supply that outputs 48 V at 5 A. (Image source: TRACO Power)

Like the 120 W version, this power supply uses a half-bridge LCC topology with a switching frequency between 75 kHz and 100 kHz. It includes active power factor correction and has a nominal output voltage of 48 V, adjustable from 47 V to 56 V. It is up to 95% efficient and has an MTBF of 1,300,000 hr.

The TIB 480-124EX (Figure 5) is a 480 W power supply with a 24 V, 20 A output and an efficiency of 95%. It comes in a package measuring 4.5" × 4.89" × 3.23" and features remote on/off capability. The output voltage is adjustable between 23.5 V and 28 V, and its MTBF is 1,300,000 hr.

Figure 5: The TIB 480-124EX 480 W power supply includes remote on/off control capability. (Image source: TRACO Power)

Conclusion

The TRACO Power TIB-EX series of DIN rail power supplies combines high-performance with reliable, efficient, and durable circuit designs optimized for control-cabinet mounting in industrial applications. They offer the distinct advantage of being qualified for use in hazardous environments.