86474-1S Reliance Electric Single‑Phase SCR Rectifier Stack

The 86474-1S is a compact, heavy‑duty single‑phase fully controlled SCR (thyristor) rectifier stack designed and manufactured by Reliance Electric (now part of Rockwell Automation). It serves as a critical AC‑to‑DC power conversion component for low‑to‑medium horsepower single‑phase DC drives, delivering precise phase‑angle control for armature and field regulation in industrial applications. Introduced in the 1980s, the 86474-1S is no longer in production and is considered obsolete; the current market supply consists of refurbished units, surplus new old stock, and tested used units. Built for reliability in space‑constrained or cost‑sensitive environments, the “S” suffix denotes a standard industrial grade configuration with integrated heat sink and gate drive hardware, optimized for 460 VAC single‑phase systems (compatible with 230 VAC). Every original unit underwent factory load testing, thermal cycling, and high‑potential insulation verification to ensure consistent performance.

The model number 86474-1S follows Reliance Electric’s standard naming convention for rectifier stacks. The prefix 86474 identifies the unit as part of the single‑phase rectifier stack family. The digit 1 indicates a single‑phase (1φ) topology. The suffix S designates a standard industrial grade configuration, featuring a single integrated heat sink assembly, standard gate drive circuitry, and no enhanced surge protection or compact modifications.

The 86474-1S is engineered for single‑phase industrial power conversion, with robust electrical ratings tailored for 460 VAC systems. It accepts a single‑phase AC input of 230 VAC or 460 VAC at 50 Hz or 60 Hz. The DC output is rated for 25–30 amperes continuous current, with a maximum output voltage of 600 VDC. The topology is a single‑phase fully controlled bridge utilizing two press‑pack SCR modules and two freewheeling diodes, ensuring efficient and precise power regulation. Full‑load efficiency reaches 96% or higher, with a maximum forward voltage drop of 1.5 V per SCR module. Insulation resistance is ≥500 MΩ when tested at 1000 VDC. It supports a di/dt rating of up to 80 A/μs and a dv/dt rating of up to 400 V/μs. Integrated protection features include RC snubbers, metal oxide varistors (MOVs), and thermal cutoffs, safeguarding against overvoltage, overcurrent, and overheating events.

Built for durability and ease of integration, the 86474-1S features a heavy‑gauge steel base with a single vertical finned aluminum heat sink for effective heat dissipation. The central carrier houses two press‑pack SCR modules, with high‑temperature thermal paste applied to minimize thermal resistance between the SCRs and the heat sink. A compact gate drive circuit board is mounted at the top of the assembly, equipped with a pulse transformer, resistors, and diodes, connected to tin‑plated copper terminal blocks that provide low‑resistance, corrosion‑resistant electrical connections. The assembly is rated IP20 for dust resistance and limited access to live parts, and it is engineered to withstand vibration from 10 Hz to 1000 Hz at up to 5 g. Its compact mounting footprint enables direct drop‑in replacement of legacy single‑phase stacks, including 86471‑R and 86467‑1R. The unit features a 2‑bolt bracket mount for secure installation in control panels or drive enclosures. Physical dimensions are approximately 203 mm × 102 mm × 76 mm (8.0 in × 4.0 in × 3.0 in), with a weight of approximately 0.91–1.0 kg (2.0 lbs).

The 86474-1S operates reliably across a wide range of environmental conditions, suitable for general industrial environments. The operating temperature range is ‑20°C to +85°C, with short‑term operation permissible up to +100°C. The storage temperature range extends from ‑40°C to +85°C. It can operate in relative humidity levels of 5% to 95%, non‑condensing, preventing moisture‑related damage to internal components. The unit is certified to withstand vibration from 10 Hz to 1000 Hz at up to 5 g, ensuring stability in machinery with moderate vibration. It can be installed at altitudes up to 1000 meters without derating; derating is required for altitudes above 1000 meters to maintain performance. The enclosure rating is IP20, providing protection against dust and accidental contact with live components, making it safe for standard industrial control panel installations.

The 86474-1S is fully compatible with Reliance Electric’s GTS, MaxPak, and S4 series single‑phase DC drives, serving as a reliable replacement for older single‑phase rectifier stacks. Typical applications include small manufacturing conveyors, material handling equipment, light‑duty DC motors, industrial machinery requiring compact, cost‑effective single‑phase AC‑to‑DC conversion, and retrofit projects for legacy Reliance DC drive systems. Its robust protection features and standard industrial design make it ideal for 230 VAC/460 VAC systems with moderate loads and limited installation space.

Original 86474-1S units are no longer in production by Reliance Electric. The current market supply consists of refurbished units, surplus new old stock, and tested used units. Refurbished units undergo complete disassembly, thorough cleaning, replacement of worn or degraded components (including SCR modules, capacitors, and gate boards), and full functional testing, including a minimum 3‑hour load test to ensure performance meets original specifications. As of 2026, market pricing for refurbished units ranges from $2,200 to $2,800, while surplus new units are priced between $4,200 and $4,900. The standard warranty for the 86474-1S is 12 months, covering defects in materials and workmanship under normal operating conditions. The warranty excludes damage resulting from unauthorized modification, improper installation, overvoltage or overcurrent events, mechanical impact, or operation beyond the rated environmental limits.