System Overview

The FCS-2000 Smart Power Supply is a three phase power supply for operating different banks of electrical resistance heater elements (such as Molybdenum, Molybdenum Disilicide, Silicon Carbide, Tungsten, etc.). The FCS-2000 is configured to control the elements over an approximate 10:1 resistance change. To enable the power supply to deliver the power at near unity power factor, multi-tapped transformers and tap switching electronics are employed on each of the three power phases brought to the power supply.

The FCS-2000 Smart Power Supply is comprised of four major components: the MS4434 Zone board, the MS4435 PSI board, the phase bank assembly and the power transformers. Each of these components will be described in detail in the following sections.

Features

The FCS-2000 Smart Power Supply has a host of features that make it the power supply of choice for sophisticated applications. With its ability to measure element resistance and then dynamically control the power delivered to those elements, the FCS-2000 can save furnace operators on operating costs and on maintenance costs by reducing the power factor component of the electric bill and by reducing the frequency of element replacements.

The FCS-2000 is the first complete power supply to offer the user data communications and monitoring capabilities for electric furnaces. A hand held terminal is included as a standard communications device to the FCS-2000. Through this terminal, the unit can be started, stopped, monitored, and tested. The output power of the FCS-2000 is commanded by a 4-20mA analog instrumentation loop. No longer is it necessary to trim the gain and the offset of the analog loop. The FCS-2000 uses digital technology to precisely read the commanded power. The terminal displays the power requested and the actual power being delivered.

The FCS-2000 is designed to prolong the life of the components both within the power supply and in the furnace. When commanded to make a major increase in output power, the FCS-2000 will ramp smoothly to the new commanded level. This is not to say that the change is accomplished over a long period of time. The change on a typical system is accomplished within 1 second. However, the power supply will not permit a step change in power level (move from one level to another in virtually zero time).

The MS4434 Zone Board

The MS4434 Zone Board performs the functions of acquiring the analog feedback for the microprocessor and controlling the individual tap switches (anti-parallel SCRs). The zone board is mounted on the phase bank assembly. All electronics for controlling a particular zone are located on this assembly and circuit board. Indicator LED lamps are provided to assist technicians in timely diagnosis and repair of the assembly.

Of particular significance is the attention to catastrophic failures in SCR powered systems. The zone boards incorporate a “watch dog” timer device that should the microprocessor fail to communicate with the zone board in the required time period, the “watch dog” will bark and shut down all of the SCR firing circuits. This prevents an out of control microprocessor from false firing the SCRs causing short circuits on the transformers. The fault tolerant design of the FCS-2000 system is one of its key features.

The MS4435 PSI Board

The MS4435 PSI board assembly is the heart of an FCS-2000. On this assembly, all power supply voltages for the zone boards and the PSI board are generated, the microprocessor is mounted here, and the interface to the outside world can be found on this board.

The power supplies found on the PSI board are wired to each of the zone boards in a daisy chain fashion. Each supply output has an LED indicator which is used in troubleshooting to assure that the proper voltages are present.

The microprocessor board is a self contained, small outline, single board computer incorporating a V25 microprocessor chip. All memory, bus hardware and peripherals are contained in this application specific single board computer.

The external interface hardware consists of board selection hardware and processor bus interface components. These essential circuits allow the single board computer to address the individual zone boards, providing the bi-directional information flow from processor to zone board and vice versa.

The Phase Bank Assembly

The phase bank assembly houses the zone board, the 4 SCR switches, and the protective MS4595 Snubber boards. The SCR switches are rated for the RMS amps they are required to deliver. They are connected together via a copper bus bar on the line side of the switch. On the load side, there is a small bus bar which connects the SCR switch to its protective fuse. Adjacent to the fuse is a snubber board whose purpose is to limit transient phenomena and prevent SCR false firing. On the top of this board are (2) Neon lamps which indicate a blown fuse – either the SCR protective fuse or the snubber protection fuse.

Output Transformers

The output transformers are located in their own section of the enclosure. The transformers are sized for the given power requirements and are manufactured for specific operations. The main design feature is that the primary winding is extended to provide a reduced output when full voltage is applied.

Unit Specifications

Input: 480v, 60Hz, 3 Phase
Output: ………………………………………………………………..61v,1900a each output, 345Kw total

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