Custom Controls and Power Factor
CUSTOM RECTIFIER CONTROL SYSTEMS (optional)

The Rectifier Control Trigger System is a combination of hardware and software that allows standard industrial microprocessor boards based on standard PC architecture to directly control the triggering of large SCR Rectifiers, while adding the benefits of computer based diagnostics to the system. The system consists of a microprocessor based control for each individual unit, some form of SCR failure monitoring system, diagnostic software, ant an operators workstation for each cell line, which provides a central point for operator information, and remote dial-up access.

Rectifier Control

The rectifier control is located in the control panel for each individual unit, and provides all of the electronic timing, triggering and protection functions for the unit. The heart of the system is an industrial PC card assembly. This consists of a single board computer in STD bus format, with PC-104 format daughter boards, that plug into an STD card rack The daughter boards include a Solid State Disk board, for holding programs and diagnostic data, an A/D input board to provide the cent and voltage feedback signals as well as the three phase synchronizing information, and a digital I/O board which processes sequence information, trigger pulse information, and diagnostic information about the various alarms circuits of the unit.

SCR Monitor

The SCR monitoring system consists of an Opto-22 serial remote "Brick" for each SCR column. This is an assembly of up to 16 isolated input modules with a communication board that allows them to be accessed through an RS485 serial communication line. The Unit Control can then read the status of every input point, and provide automatic load cutback with SCR failures, and alarm indication for each new SCR and its fuse. This gives blocking voltage information to the input module which gives an On indication for a good fuse, whenever the unit is energized. LEDs on each input module provide a direct visual indication. Dv/dt fuses and Thermal switches are also monitored on each column.

Unit Diagnostics

At any time the Coml: serial port of the unit microprocessor can communicate in "terminal" mode to provide diagnostic information on the operation of the unit. Any computer that can run VT100 terminal emulation software may be connected to this port for this purpose. This gives access to the following screens of information.

1.	A parameter screen with current operating information.
2.	An event screen with all control and alarm events
3.	An SCR status screen with the results of the SCR monitor system
4.	A ripple screen with a one cycle snapshot of each cabinet's current waveform.
5.	A control constant screen for adjusting control and alarm settings on line
6.	A test screen for additional test and maintenance information.

Operators Workstation

Each unit connects to an RS-485 serial communication line to the control room. An industrial panel mount PC in the main control panel communicates to all three units of a cell line over this circuit. This allows a special program to display the above diagnostic information, for all three units, on a single screen. The output is shown on a graphical plot, and saved in a disk file for each day's run. A high speed modem allows dial-up access to the operating information from any location.

Test Features

When the unit is shut down, a special test mode allows turning on gate signals for Bating checks. Also a special open circuit test mode allows powering up the unit with firing angle control rather than the normal current control. Voltage dividers from inside the power cabinets allow simple confirmation of voltage waveforms.

PLC Based Controls are available.

All PC Boards and Controls are designed and manufactured by Neeltran.

PLC Based Controls for Power Supply

Typical Large Power Supply Control Arrangement