Accident analysis and preventive measures of high-voltage inverter

Accident analysis and preventive measures of high-voltage inverter

Due to the high power of the inverter and the large amount of heat generated, in order to ensure sufficient ventilation and cooling effects, a set of integral fans were independently installed on the top of the inverter power cabinet and transformer cabinet. Ensure the overall cooling and ventilation requirements of the inverter.

The connection between the motor and the fan is shown in Figure 1. The hydraulic coupling between the original motor and the fan is removed, and a steel shaft is added between the motor and the fan. The connecting shaft is a hollow steel shaft. The transmission mode of the blower is changed to the direct coupling drive of the intermediate shaft, and the original elastic pin coupling is changed to the diaphragm coupling. Between the two pairs of diaphragm couplings, a hollow connecting shaft and membrane are installed. The model of the disc coupling is form01-2501, the model of the intermediate shaft is x430.10, its length is 1572mm, and the total weight of the transmission components is 539kg. The transmission mode of the induced draft fan is changed to the direct shaft intermediate drive. In this transformation, the original elastic pin coupling is also changed to the diaphragm coupling. A hollow is installed between the two pairs of diaphragm couplings. The connecting shaft, the model of the diaphragm coupling is form11, the model of the intermediate shaft is x429.10, its length is 1750mm, and the total weight of the transmission components is 649kg. In addition, the inlet baffle door of the induced draft fan is changed from manual control to electric control to meet the needs of power frequency adjustment. This omits the cost of motor displacement and production foundation, saving the renovation funds.

Figure 1 On-site electrical wiring diagram of the high-voltage inverter is equipped with 4 sets of lead and supply inlet baffle actuators. Induce and blower frequency conversion control logic and inlet baffle control logic in the dcs system, and modify the operation screen. According to the requirements of the technical management department, improve and modify the logic of interlocking, protection, sequence control, etc. of the induction, blower and inlet baffle.

System comparison before and after transformation (1) The speed regulation range of the dhvect-di02000 / 06 frequency converter is 0-100%; the speed regulation range of the hydraulic coupler is generally 40-95%, that is, the high-speed section causes about 5% speed loss, Affect the output of the unit. The minimum value of the hydraulic coupling is generally only 40% of the rated speed.

(2) The dhvect-di02000 / 06 type inverter has higher efficiency (more than 97%) in the entire speed regulation range, and the lower the efficiency of the hydraulic coupler at low speed. It itself brings no small loss, and the energy saving effect of speed regulation is greatly reduced.

(3) The dhvect-di02000 / 06 frequency converter realizes a real soft start to the motor and the load machinery, completely solving the problem of starting shock. If the work requires, the motor can be restarted multiple times in a short time. The hydraulic coupling cannot solve the problem of motor starting. The motor is still directly started, the starting current is large, and it cannot be started frequently.

(4) When using dhvect-di02000 / 06 type inverter to adjust the speed of the motor, just disconnect the original switch and the connecting cable of the motor and add the inverter, the transformation scheme is simple.

(5) The dhvect-di0200 / 06 inverter is a high-tech equipment with high reliability and basically maintenance-free. The hydraulic coupler is a mechanical device, which contains multiple systems such as oil and water channels. It has a high failure rate and a large maintenance workload, resulting in a reduction in effective production time.

The total cost of this frequency conversion renovation is 4.45 million yuan. After the 4 frequency converters are put into operation, according to the meter reading statistics of the operating personnel, compared with the same power generation before the conversion, the daily saving can be 27,900 kw / h, only saving electricity costs The investment in inverter reconstruction can be recovered within a year and a half, and the energy saving benefit is considerable. Therefore, the transformation of high-voltage frequency conversion device is the most direct and effective measure to save energy, reduce consumption, tap potential and increase efficiency, and improve comprehensive economic benefits. The superior speed regulation performance and remarkable energy-saving effect of the high-voltage inverter have been verified and approved.

Experience in construction and transformation (1) The transformation project of No. 8 machine lead and blower is equipped with inverter, the installation and construction is simple, that is, the frequency conversion device is inserted between the original high-voltage switch cabinet and the motor, and the original wiring is not changed much;

(2) The operation of the inverter is easy to use, and the operation of the inverter is only simple on, off and frequency adjustment;

(3) The frequency conversion device can perform stepless speed regulation, the speed regulation range is wide, and the speed regulation accuracy is high, and the applicability is strong;

(4) The protection function of the frequency conversion device is perfect, the equipment failure rate is low, the fan starts smoothly, the starting current is small, and the reliability is high;

(5) The motor does not require long-term high-speed operation, the working current is greatly reduced, the power saving effect is obvious, and the service life of the motor itself is greatly extended;

(6) Since the frequency converter replaces the hydraulic coupler for speed regulation, the defect of high failure rate of the mechanical and hydraulic coupler is eliminated, and the equipment maintenance cost is greatly reduced;

(7) Since the starting current of the motor is very small, the motor can be started frequently, the vibration and noise of the motor are significantly reduced, and the bearing temperature is also greatly reduced.

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