Based on practical experience and lessons learned, this article outlines key considerations when designing programmable control systems.
1. At least 75% of the technology used in a system should be mature. This includes programmable controller products or similar designs that have been tested in production, or technologies that are expected to be validated in future projects. Additionally, the design team must have the necessary expertise or the ability to master the required technology. It is essential to ensure that the chosen hardware and software solutions are reliable and maintainable. Once a control system is implemented, it is often difficult to make significant changes later, so hidden issues may remain undetected until they cause serious problems under certain conditions.
2. The system’s hardware structure and network configuration should be simple and clear. Avoid unnecessary complexity in hardware design and limit the number of network connections. Use the built-in networking capabilities of the programmable controller wherever possible. When creating I/O chassis templates, keep them simple and consistent, with moderate density. Avoid excessive junction points, as high wiring density can complicate manufacturing and maintenance processes.
3. Clearly separate the functions of the control system and the management system. Process control systems using programmable controllers require high real-time performance. While network communication may temporarily fail, it can usually be restored. However, during such periods, the controller may lose control, leading to unpredictable consequences. In large systems using multiple controllers, it's better to use direct hardware interlocks, especially for critical commands like emergency stop. If one system fails to transmit the stop command, the other might continue running, which could lead to dangerous situations. To ensure safety, the emergency stop signal should first cut off the actuator power before sending the signal to the controller.
4. The program written for the programmable controller should be concise and easy to read. User software should be structured in a way that resembles a series of "black boxes," each containing clearly defined and logical statements. Each statement should be straightforward and avoid overly complex logic. Using too many special conditions or complicated relationships can make the code hard to understand and maintain. Ensuring that the software is readable by most engineers is crucial for long-term usability and troubleshooting.
5. The programmable control system should include key monitoring features. While color graphics workstations can provide visual feedback, they may not always be practical due to cost or time constraints. For critical faults or high-risk equipment, digital output indicators can be used to monitor system status. These indicators, placed near the relevant components, help operators quickly identify normal operation or potential failures, ensuring timely responses.
6. When designing large or medium-sized systems, avoid exhausting all available hardware and software resources. Reserve at least 15% of hardware capacity for future expansion. In software development, estimate resource usage carefully, especially for intermediate relays, counters, and timers. After commissioning, software often requires updates or rewrites, so flexibility is important. A rigid, unchangeable system is not practical for real-world applications.
7. Redundancy is an essential part of designing reliable programmable control systems. Common methods include dual-system hot or cold standby configurations. Full redundancy—where both the central processor and all input/output modules are duplicated—is expensive and may not be feasible in many projects. However, in hazardous environments like chemical plants, full redundancy may be necessary. The goal is to minimize the impact of failures, ensuring that a single component failure does not disrupt the entire process. By carefully planning redundancy, designers can create more robust and reliable systems.
These considerations highlight the importance of thoughtful and thorough planning when designing a programmable control system. Only through careful attention to detail can engineers ensure that their systems perform reliably and safely over time.
First, basic concepts
A Power Inverter is a power electronic device whose primary function is to convert direct current (DC) to alternating current (AC). This conversion is critical in a variety of application scenarios, especially where DC power (such as solar panels, battery packs, etc.) needs to be converted to AC power for use by household appliances, industrial equipment, or power systems.
Second, the working principle
The inverter is quickly switched through internal electronic switching devices (such as MOSFETs, IGBTs, etc.) to produce alternating current close to sine waves. These switching devices operate according to specific control strategies to ensure that the output AC has a stable voltage, frequency and waveform quality.
3. Key parameters
The performance of the inverter can be evaluated by the following key parameters:
Rated power: The maximum power that the inverter can continuously output.
Conversion efficiency: The proportion of energy lost during the conversion of direct current to alternating current by the inverter.
Output voltage/frequency: The voltage and frequency of the AC output by the inverter.
Waveform distortion: The degree of difference between the inverter output waveform and the standard sine wave.
Protection function: inverter built-in overload protection, short circuit protection, overtemperature protection and other safety functions.
Solar system inverter, solar power inverter, DC power inverter
Foshan Keylewatt Technology Co., LTD , https://www.klwenergy.com