It can be seen from Fig. 4 that the maximum inrush current at startup is about 55A, the intrusion time is about 54ms, and the constant is 8A.
Figure 5 Motor voltage and current waveforms
It can be seen from Fig. 5 that the current hysteresis voltage is about 0.9 ms, and the power factor is 0.96.
The experimental results are basically consistent with the test requirements. If the optimization algorithm programming is not adopted, the power requirement is very high, so the control system can be applied and implemented, which virtually reduces the cost.
5, improved advantages and maintenance
Obviously, after the above improvements, there are the following advantages:
- After using PLC, the versatility is greatly improved, the previous single PLC is improved, and the training period of the staff is shortened;
Replace the traditional hard PLC with an embedded soft PLC, and the external circuit is simplified;
Modularization enables a variety of complex control systems to easily add and change control functions;The PLC can perform automatic fault detection and alarm display to improve operational safety and facilitate maintenance;
Easy group control and improve operation efficiency;There is no need to change the external line when changing the control scheme.
Things to be aware of for testing and maintenance:In order to improve system efficiency and reduce overhead, use I/O as little as possible;
Have emergency stop and appropriate interlock button links;Input and output cannot use the same cable;
DC inductive load parallel surge diodes to extend contact life; AC inductive load shunt capacitor absorber to reduce noise. In order to ensure the reliability of the control system work, do a good job of grounding, dustproof, oil-seeking and radiation protection.
Conclusion
This system can be used for testing of relays, motors, inductors, chargers and other products. After the improvement, there are still the following defects: First, if the load is broken, it cannot detect and protect itself; if the load is short-circuited, the product will generate overcurrent in a short time, which may cause product damage or even threaten personal safety. Second, data collection is incomplete and cannot be monitored in real time. The use of ammeter can make up for the shortcomings of the first point; real-time data acquisition can be realized by using data acquisition card.
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