8406-113 EGCP-3 Woodward Digital Controller 8406113

Description

This manual describes the Woodward EGCP-3 Engine Generator Control Package, Load Sharing (LS) model, part number 8406-113. It provides description, operation, tuning, and troubleshooting information for EGCP-3 digital controls. The details on installation, wiring, communication, Regulatory Notes and Warnings are in the EGCP-3 Installation Manual 26122.

The EGCP-3 LS is intended for power generator applications where multiple control/generators will supply an isolated bus, or operate in parallel with a Mains (Utility) bus. The EGCP-3 can perform engine start/stop sequencing. For isolated load operation, the control will operate in isochronous speed control. For a multiple engine bus, up to 16 generators can share load, operate in BaseLoad, or process control modes.

The design principles of DCS and PLC differ greatly. PLC is developed from the principle of relay control, which stores instructions for executing logical operations, sequential control, timing, counting, and arithmetic operations; And control various machinery or production processes through digital input and output operations. The control program developed by the user expresses the process requirements of the production process and is stored in the user program memory of the PLC in advance. Execute the stored program item by item during runtime to complete the operations required by the process flow.

There is a program counter in the CPU of the PLC that indicates the storage address of the program step. During the program operation, the counter automatically increases by 1 when one step is executed. The program executes sequentially from the starting step (step number is zero) to the final step (usually the end instruction), and then returns to the starting step for cyclic operation. The time required for the PLC to complete each cycle operation is called a scanning cycle. Different models of PLCs have cyclic scanning cycles ranging from 1 microsecond to several tens of microseconds. The loop operation of program counters is something that DCS does not have. This is also the reason why the redundancy of PLC is not as good as that of DCS. DCS was developed on the basis of operational amplifiers. Make all the relationships between functions and process variables into functional blocks (some DCS systems are called puffed blocks). The main difference between the performance of DCS and PLC is in the logical calculation of switching values and the operation of analog quantities. Even though the two have some infiltration into each other later, there are still differences.

After the 1980s, in addition to logical operations, the algorithm functions used in the control circuit of PLCs have been greatly enhanced. However, PLCs use ladder diagram programming, and the calculation of analog quantities is not very intuitive during programming, making programming more cumbersome. However, in terms of solving logic, it exhibits the advantage of being fast. In the microsecond scale, solving 1k logic programs takes less than 1 millisecond. It processes all inputs as switching variables, with 16 bits (also 32 bits) being an analog variable. And DCS treats all inputs as analog quantities, with one bit being the switching value. Solving a logic is on the order of several hundred microseconds to a few milliseconds. For PLC, solving a pid operation takes tens of milliseconds, which is comparable to the operation time of DCS. In terms of grounding resistance, the requirement for PLC may not be high, but for DCS, it must be below a few ohms (usually below 4 ohms). Analog isolation is also very important. For systems with the same I/O points, the cost of using PLC is lower than using DCS (approximately 40% savings).

PLC does not have a dedicated operating station, and the software and hardware used are universal, so the maintenance cost is much lower than that of DCS. If the controlled object is mainly equipment interlocking and there are relatively few circuits, using PLC is more suitable. If it is mainly analog control and there are many function operations, it is best to use DCS. DCS is much better than PLC in terms of redundancy in controllers, I/O boards, communication networks, and other advanced computing and industry specific requirements. Due to the use of universal monitoring software, PLC is easier to design management information systems for enterprises.

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