Transformation of the most popular PI7000 frequenc

2022-08-07
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Transformation scheme of puchuan PI7000 frequency converter in sugar mill crusher I. overview in China's sugar industry, frequency converter has been widely used in variable torque loads such as fans and water pumps, and achieved remarkable energy-saving results. As an important production equipment in sugar factory, the press has been running at a constant speed with the traditional control mode. In fact, from the aspects of production process and energy saving, the technical transformation of the press is not only effective, but also can improve the enterprise benefit

II. Production process analysis

it is well known that the yield of the press is one of the main factors affecting the total sugar yield. If the yield of the press is increased by 1%, the total recovery is increased by 0.88%~0.92%. The factors that affect the extraction rate mainly include the following reasons:

1. when the fiber in sucrose leaves the outlet of the press after being pressed, it expands again. At this time, the pressed fiber will absorb part of the pressed juice at the outlet with its own expansion. At the same time, affected by the machine efficiency, the sugar in sugarcane cannot be fully squeezed, which forms the sugar loss in bagasse

2. the crushing degree and shape of sugarcane are the premise to ensure the extraction of the first press. The sugarcane has good crushing degree, the sugarcane juice is easy to press out, and the seepage effect is improved

3. reducing the moisture content of bagasse is the guarantee to improve the extraction

4. it is very important to ensure the uniform thickness of sugarcane layer transported from the shredder to improve the extraction rate. If the sugarcane layer is too thick and the

crushing is not complete, the bagasse will be wasted; If the sugarcane layer is too thin, it will not dry the sugarcane layer, and the bagasse moisture is too high, which will affect the extraction rate

5. in the later stage of the press season, the wear of the press roll is becoming more and more serious, which leads to the expansion of the gap of the press roll and the decrease of the extraction rate

in conclusion, since the speed of the press is not adjustable, the thickness of the sugarcane layer conveyed from the shredder will not meet the requirements for about 10% of the time, which will make the average extraction rate of sugarcane juice lower than 95.4%. The lower the extraction rate, the greater the juice loss, resulting in lower yield. If the speed of the press can be adjusted, when the backwardness of the sugarcane layer is not enough, press the sugarcane layer after it reaches the normal thickness by reducing the motor speed of the press. In this way, the press will be more sufficient, and the average extraction rate will be increased by more than 0.2%. At the same time, due to the reduction of the speed, the current will drop, so as to achieve the purpose of energy saving and power saving. Universal frequency converter is the best device to solve this problem

III. working condition before transformation

there are five presses in one factory, and the technical parameters are as follows:

serial number, rated power, rated current, rated speed reduction ratio

1 320kw 565a 976rpm 1:28.5/1:4

2 280KW 503A 980rpm 1:30/1:4.17

3 250KW 451A 980rpm 1:31.5/1: 4.17

4 250KW 451A 980rpm 1:31.5/1:4.17

5 320kw 565a 976rpm 1:28.5/1:4

calculated by 2700 tons per day, The pressing season is 5 months, and the total pressing capacity is 400000 tons of sugarcane; The sugar content of sugarcane is between 13.6% and 16%, and the average value is 14.5%; The extraction rate is between 95.5% and 96.2%, and the average value is 95.8%; Cooking is calculated as 86%. According to the actual measurement, the power consumption per ton of sugarcane is about 30 degrees. The motor is started by frequency sensitive resistor

IV. transformation scheme

the whole transformation system of the press consists of the original electric control cabinet, frequency conversion cabinet and new electric control cabinet. The original electric control cabinet is the power frequency starting cabinet, and the frequency conversion cabinet adopts the puchuan technology PI7000 320m3 frequency converter. This cabinet and the newly added electric control cabinet group 3. Brake pedal force: 390n, 340n form a new system. The control panel is equipped with system selection switch, industrial frequency conversion selection switch, frequency conversion power transmission button, electrical start button and current setting button

1. the self-adjusting transformation system of the press is equipped with: operation and adjustment of the original system, power frequency startup of the new system, variable frequency

startup of the new system, and automatic control of the new system

2. manual control: install a frequency conversion cabinet and a frequency conversion cabinet for each motor. The capacity ratio of frequency conversion cabinet

motor capacity is amplified by one level to ensure the safety and reliability of the system. In case of failure or abnormal phenomenon of the frequency conversion cabinet, the system can be switched to the original starting cabinet through the frequency conversion cabinet, so that the press can produce normally and continuously. The frequency conversion cabinet is also equipped with an AC reactor, which can effectively suppress the influence of harmonics on electricity, sometimes much lower than the absolute humidity in the atmosphere, and protect the frequency converter from the impact of electric surge voltage

3. constant current automatic control: according to the analysis of the production process, it is very important to ensure the thickness of the sugarcane layer

in order to improve the extraction rate, that is to say, the smaller the current fluctuation range of the motor, the better. On the basis of the above driven system, the hall sensor is added to detect the actual current of the motor as the feedback signal of the frequency converter, which controls the motor speed according to the feedback signal. If the sugarcane layer is too thick, the current of the motor becomes larger, and the frequency converter will increase the speed of the motor, so that the sugarcane layer can be pressed as soon as possible; If the sugarcane layer is too thin and the current of the motor becomes small, the frequency converter will reduce the speed of the motor so as to press the sugarcane layer as thoroughly as possible. In this way, the motor current always fluctuates in a small range, so as to ensure the uniformity of sugarcane layer thickness and help to improve the extraction rate

4. nuclear scale signal feedback full automatic control: the sugarcane layer is measured by the nuclear scale and then sent to the press by the conveyor belt for pressing. The nuclear scale outputs 0~5v signal to the governor. The governor adjusts the speed of conveying the plastic granulator technology belt that vigorously develops the use of renewable energy and industrial waste heat according to this signal to ensure the uniformity of sugarcane quantity. On the basis of the above driven control system, the signal of the nuclear scale is fed back to the frequency converter. The frequency converter will adjust the speed of the press according to the amount of sugarcane. The large signal of the nuclear scale indicates that the sugarcane layer is thick, and the frequency converter will increase the speed of the motor; The small signal of the nuclear scale indicates that the sugarcane layer is thin, and the frequency converter will reduce the speed of the motor, so as to ensure the uniform thickness of the sugarcane layer and help to improve the extraction rate

v. benefit analysis after transformation

1. increase of extraction rate: according to the calculation, the average extraction rate can be increased by more than 0.2%. Now, it is conservatively estimated that the extraction rate can be increased by

0.1%. According to the annual extraction of 400000 tons of sugarcane, the sugar content is 14.5%, and the boiling yield is 86%: 400000 tons of sugar *14.5%*0.1%* 86%=50 tons in each pressing season. According to 2700 yuan/ton of sugar: 50 tons *2700 yuan/ton =135000 yuan. That is to say, the increase in output has enabled the enterprise to generate more than 135000 yuan in each pressing season, which is almost blank in most places

2. power saving: the total installed capacity of five Juicers is 1420kw. According to the calculation, after the transformation, the power consumption per ton of sugarcane is reduced by 2 degrees. Calculated by 400000 tons of sugarcane per year: annual power saving: 400000 tons *2 degrees/ton =800000 degrees. Calculated by 0.52 yuan/degree: 800000 degrees *0.52 yuan/degree =416000 yuan

3. investment return period: the budget of the whole system is about 700000 yuan, 135000 +416000 =551000 yuan. It can be seen that the whole frequency conversion transformation

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