1 Introduction

　　This case comes from the electrical project of the heavy oil catalytic cracking unit of Shandong Chengda New Energy Technology Co., Ltd. that our company serves. Due to the key role of the main fan unit in the catalytic cracking process, the control and protection of the main fan unit have always been people's attention, especially the large-scale axial flow fan, which has many and strict restrictions on the stable working condition area, and once it fails, economic losses will be caused. It is so heavy, so the control and protection of the axial flow fan has always been the focus and difficulty in the automatic control design.

　　2. Outline plan

　　The motor of this project is a 14000KW 10KV motor, rated current: 914A. The starting current is required to be 2.5 times the rated current. The drag load is the main exhaust fan of the oil catalytic cracking project. The protection functions mentioned by the customer include: high-voltage power supply phase loss, under-voltage protection, starting over-current, starting overtime, starting loss-of-load, and thyristor fault protection. Other requirements: There must be a standard RS-485 communication interface. The secondary control power supply is AC380/220V. The color of the product is: RAL7032. The company finally selected our company's GGQ series of high-pressure solid-state soft-start devices. According to customer requirements, we drafted a plan as follows:

　　rate generator set load test device.

　　3. Overall plan and working principle

　　The overall plan is to combine soft-start cabinets (2200*1500*2300) and star point cabinets (1000*1500*2300). The star point cabinet is on the right side. The star point cabinet is equipped with three current transformers (model, transformation ratio and switch). The cabinet is the same) for the differential protection of the motor, and the soft starter is separately installed with a current transformer for the soft start current detection. The total size of the set of products is 3200*1500*2300 (width * depth * height).

　　Its workflow is as follows:

　　The operating cabinet breaker QF1 station is closed, and the starting signal is sent to the soft starting cabinet. The soft starting cabinet receives the starting signal, and the soft starting cabinet executes the soft starting process. There is no abnormal situation during the starting process, and the closing command is sent to the star point cabinet QF2 to close brake. The star point closing gives a feedback signal to the soft-starting cabinet, and the start is completed. When the starting is abnormal, jump to the operating cabinet during the starting process, and after the abnormal phenomenon is eliminated, wait for the interval and then restart the car according to the above-mentioned work flow until the soft start is successful and the soft start is over.

　　4. Operation status

　　Since the GGQ series of high-voltage solid-state soft starter was put into use in the company, the operating parameters of the main exhaust fan have been within the normal range, and the motor has achieved soft start, reducing the impact of the large motor starting on the power grid, and conforming to relevant technical standards Requirements, reduce the impact force generated when the motor starts, effectively extend the life of the motor, meet the various protection functions proposed by customers, greatly reduce the failure rate of the fan, improve the safety and reliability of equipment operation, and reduce the workload of equipment maintenance .