General Overview
The S&C Source-Transfer PMH Pad-Mounted Gear is a compact, self-contained switching and protection package designed for automatic source transfer and fault protection in distribution systems. It is suitable for small- to medium-sized industrial, commercial, and institutional complexes, offering a reliable and economical alternative to traditional overhead transfer schemes and metal-enclosed switchgear.

Specifications and Features
The gear is available in two models, PMH-6 and PMH-9, providing three-pole automated switching for source circuits up to 600 amperes and single-pole switching for load feeders up to 400 amperes. It includes built-in voltage sensing, control power, automatic controls, interrupter switches, stored-energy switch operators, and fuse mountings. The system is factory-assembled and tested, ready for installation without external wiring or control power.

Micro-AT Control
The Micro-AT Source-Transfer Control is a microprocessor-based system that monitors voltage sensors to assess power source conditions. It initiates switching to an alternate source if the primary source fails, ensuring continuous power supply. The control is field programmable for customization to maximize power service and conform to utility practices.

Switching and Protection
S&C Mini-Rupter Switches handle live-switching duties on incoming source circuits, offering high fault-closing ratings and flexibility. The switches can close into fault currents twice, maintaining operability and the ability to carry and interrupt rated currents. Stored-energy switch operators enable high-speed operation, enhancing reliability.

Fusing Options
The gear uses S&C Power Fuses with Uni-Rupter for load feeder protection, offering various ampere ratings and time-current characteristics for precise coordination. Fault Fiter Electronic Power Fuses provide advanced protection and coordination through electronic control modules.

Applications
The gear is suitable for critical loads requiring high service continuity, such as hospitals and industrial plants. It supports primary-selective service from two radial feeders or double-circuit looped-primary feeders, allowing for automatic or manual retransfer to the preferred source, with options for open or closed transition.

System Configurations
The document describes configurations for power distribution systems, including double-circuit looped-primary feeders and source-transfer pad-mounted gear, designed to provide primary-selective service to critical loads, ensuring continuous power supply even during faults or interruptions.

Operational Procedures
The source-transfer controls are programmed to initiate automatic transfer operations when power is lost or reduced, ensuring quick restoration to an alternate power source. Sectionalizing switches and manual units manage power distribution and isolate faults.

Safety Features
Safety features such as unbalance detection and overcurrent lockout protect the system from faults and prevent disturbances on the utility's distribution network. The source-transfer control continuously monitors voltage levels to maintain system stability.

Components
The gear includes components designed for durability and safety, such as insulated roofs, glass-reinforced polyester barriers, and aluminum bus connections. It features a Penta-Latch mechanism for secure door latching and protection against tampering.

Control System
The Micro-AT Source-Transfer Control provides reliable automatic transfer capabilities, monitoring power source conditions and initiating switching operations to maintain service continuity. It efficiently handles common-bus primary-selective systems.

Design Features
The control system incorporates solid-state electronic circuitry with metal-oxide surge protectors for optimal surge protection. It undergoes rigorous testing to ensure durability and performance, including ANSI Surge Withstand Capability Test and a severe capacitive-discharge test.

Operational Components
Components include indicating lamps for source voltage, test menu keys, and manual/automatic operation selectors. Stored-energy operators provide high-speed automatic source transfer and circuit interruption.

Optional Features
Optional features enhance system flexibility, including remote-control receptacles, anti-paralleling devices, auxiliary switches, and key interlocks for safety compliance.

Testing and Maintenance
The system includes provisions for functional testing and exercising of switch operators without affecting medium-voltage circuits. Decoupling mechanisms allow for convenient testing and maintenance, ensuring reliability.

Conclusion
The S&C Source-Transfer PMH Pad-Mounted Gear and Micro-AT Source-Transfer Control offer robust, versatile solutions for critical power applications, ensuring high service reliability and operational flexibility.