Ruggedized Hazloc Power Supplies for Mission-Critical Systems

Class I Division 2 (under North American NEC 500 standards) covers environments where flammable gases, vapors, or liquids are handled, processed, or used, but are normally confined within closed containers or systems and can escape only in case of accidental rupture, breakdown, or abnormal operation. In contrast, ATEX Zone 2 (EU Directive 2014/34/EU) and IECEx Zone 2 (International) define locations where an explosive gas atmosphere is not likely to occur in normal operation and, if it occurs, will exist for a short period only.

To qualify power supplies for these areas, manufacturers must eliminate potential ignition sources. This involves using non-sparking components (such as solid-state relays instead of mechanical relays), hermetically sealing or potting active semiconductor switches, maintaining strict surface temperature limits (T-Ratings T1–T6), and verifying creepage/clearance distances under UL 121201 and EN/IEC 60079-7. Astrodyne TDI engineers HazLoc platforms to dual-certify across both North American and ATEX/IECEx frameworks, facilitating smooth global deployment for equipment OEMs.

Hermetic encapsulation involves completely casting active power electronics inside a high-performance thermosetting polymer resin, such as thermally conductive polyurethane or silicone. This potting process creates an impenetrable physical barrier that accomplishes three critical engineering objectives:

• Atmospheric Isolation: Prevents explosive gases, moisture (IP67/IP68 rating), and corrosive chemical agents (such as Hydrogen Sulfide $H_2S$, sulfur dioxide, and salt spray) from contacting high-voltage electrical nodes, thereby eliminating ignition risks and corrosion-induced trace failures.
• Thermal Management: Void-free potting materials possess higher thermal conductivity than ambient air, efficiently transferring heat from internal MOSFETs, diodes, and planar magnetics directly to the metallic outer chassis or cooling plate, preventing localized thermal hot-spots.
• Mechanical Hardening: Encapsulated components are completely immobilized, allowing the power supply to effortlessly endure heavy mechanical shock (up to 40G) and continuous low-to-high frequency vibration under MIL-STD-810H standards without cracking solder joints or flexing PCB traces.

Yes, liquid cooling is actually the preferred cooling methodology for high-kilowatt HazLoc systems. In hazardous areas, equipment is typically mounted inside completely sealed NEMA 4X, IP66, purged (Type Z/Y), or explosion-proof cast aluminum enclosures. Placing a traditional forced-air cooled power supply inside a sealed box causes heat to rapidly build up, forcing significant power derating or thermal shutdown.

Liquid-cooled power supplies, such as Astrodyne TDI’s LiquaBlade™ platform, route liquid coolant (water-glycol mixtures or synthetic oils) through integrated internal cold-plates. Heat generated by power conversion is directly removed from the cabinet via fluid circulation without requiring air exchange with the ambient hazardous atmosphere. This eliminates external cooling fans—which are notorious ignition risks and dust collectors—and enables continuous full-rated power output in high ambient temperatures (up to 70°C fluid inlet).

HazLoc power supplies employ redundant hardware-level and electrical safeguards to ensure that no electrical fault or internal component failure can generate an arc or elevated surface temperature capable of igniting surrounding gases:

• Active Soft-Start & Inrush Limiting: High-power NTC thermistors or active MOSFET bypass circuits suppress high current spikes during startup, preventing contact arcing.
• Redundant Over-Voltage & Over-Current Protection (OVP/OCP): Independent secondary control loops instantly shut down output pulses if feedback loops fail, preventing over-voltage stress across downstream load components.
• Extended Creepage & Clearance Spacing: Circuit board layouts exceed standard industrial spacing to prevent high-voltage dielectric arc-over across PCB traces under humid or conductive dust conditions.
• Thermal Cut-Off Sensors: Multi-point thermal sensors monitor internal transformer windings and heatsink temperatures, triggering an automatic soft-shutdown before surface temperatures exceed the maximum allowable T-Rating.

Industrial processing facilities and chemical refineries are frequently subjected to momentary grid voltage sags caused by nearby lightning strikes, heavy motor startups, or grid switching transients. A conventional power supply without sag ride-through protection will drop its DC output voltage during a 200 millisecond line drop, causing critical process controllers, PLC safety loops, and emergency shut-off valves to reset.

In a hazardous area, an unexpected controller reset can cause uneven reaction pressures, gas venting, or tool aborts resulting in severe downtime and safety hazards. Astrodyne TDI designs HazLoc power supplies to comply with the SEMI F47 voltage sag immunity standard, utilizing high-energy hold-up capacitor banks and wide-input PFC boost stages that keep the DC output within tight voltage regulation during AC input sags down to 50% of nominal voltage.

High-frequency switching power supplies naturally generate conducted and radiated electromagnetic interference (EMI). In densely packed industrial HazLoc cabinets containing delicate microprocessors, wireless sensor nodes, and intrinsic safety barriers, unfiltered EMI can corrupt sensor readings or cause false triggering of safety relays.

Integrated low-pass EMI filters (incorporating common-mode chokes and X/Y safety capacitors) attenuate conducted noise on AC and DC power lines before it can propagate throughout the facility line network. By controlling conducted emissions to CISPR 32 / EN 55032 Class B limits, Astrodyne TDI ensures that the power converter will not interfere with nearby explosion-proof instruments, telemetry radios, or emergency shutdown systems.

Mechanical fans are the single most common point of failure in industrial power supplies. In heavy industrial and HazLoc environments, cooling fans draw in conductive airborne dust, moisture, chemical fumes, and debris, leading to bearing wear, fan lock-up, and catastrophic power supply overheating. Furthermore, spinning fan blades and motor windings introduce potential mechanical spark hazards.

Conduction-cooled HazLoc power supplies eliminate cooling fans entirely. Instead, heat-generating components are thermally coupled to an aluminum baseplate that mounts directly to the customer’s cabinet wall, external heatsink, or liquid plate. This design enables a completely sealed, maintenance-free enclosure structure that achieves IP65/IP67 ingress protection, high Mean Time Between Failures (MTBF > 500,000 hours), and zero acoustic noise.

Every standard and custom HazLoc power supply manufactured by Astrodyne TDI is delivered with comprehensive compliance documentation to simplify safety audit sign-offs for system integrators. Documentation packages include UL/cUL Certificates of Compliance (UL 121201 / CSA C22.2 No. 213), ATEX / IECEx EU-Type Examination Certificates (EN IEC 60079-0 / EN IEC 60079-7), CE and UKCA declarations, RoHS/REACH material compliance statements, full factory burn-in test reports, and detailed thermal derating curve datasheets.