Presco has worked in the area of AC power generation and distribution (from low power up to 100KW) and we have extensive experience in DC power conversion. An example of a combined AC/DC design is a 1 kW portable generator with demanding thermal requirements. In order to achieve high fuel efficiency over a wide range of output power, the engine in this product operates at variable speed, so the generator output varies considerably in both frequency and voltage.
Conversion to DC also needs to be highly efficient so that thermal dissipation of the circuitry doesn’t limit performance, especially at the extremes of the military temperature specification. The entire system weighs barely 30 pounds, including a battery pack that is used for automatic engine start and for load regulation. Battery management becomes more complex at the temperature extremes, so this capability is also built into the circuit card.
High-power circuits are often built on metal core or metal-backed circuit cards in order to manage the thermal dissipation of the main power components. A recent example involved a portable power distribution device designed to meet Army requirements. This product takes in three-phase 208Y/120VAC 50/60Hz and distributes phase-balanced single-phase and three-phase power. Phase balance circuitry detects imbalance of the loads and automatically rotates phases to present a balanced load to the generator.
Presco designed an innovative high-power AC switch that executes a sub-microsecond phase exchange with zero voltage discontinuity. This eliminates kick-back (voltage spikes) from inductive loads such as motors, improving performance and reliability. The switch is 5x less expensive than its conventional counterpart and dissipates about half the energy. A metal-backed circuit card provides good heat transfer to the system side rails while eliminating hot spots in the circuitry. This provides reliable operation over the entire temperature range of -40°F to 135°F. The key features of this system include: automatic phase balancing (APB); improper ground detection (IGD); input and output connector status (to prevent arcing); monitoring of voltage, frequency, temperature and over-current; Ethernet and serial communications to support an external user interface for configuration and status (webpage and serial device); and special modes for fault-tolerant battlefield usage.
Presco can supply a team to see your project through the entire development process including system architecture, circuit and software development, prototype build and debug, certification testing, design for manufacturing, in-circuit test, and pilot production. Our team has experience in solving your most challenging power conversion problems.