Application of the hottest Senlan frequency conver

2022-08-06
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The application of Senlan frequency converter in the cement product industry

[editor's note] this paper introduces the frequency conversion and speed regulation transformation of the building materials industry. First, it describes the process of the cement pipe making machine, and then focuses on the transformation, precautions and energy saving after the transformation

I Overview

with the rapid development of the national economy, cement and its products have played a huge role in the field of infrastructure, and its industry is showing a vibrant and prosperous scene. However, the equipment of this industry was learned and introduced from abroad earlier, and the time of equipment localization was also earlier, which had been finalized in the 1970s. Over the years, most equipment manufacturers have not adjusted their product structure, carried out in-depth development, and did not continue to introduce new technologies. Instead, they continue to use the technologies of the 1970s for production. Most of the speed regulation methods are electromagnetic speed regulation, resulting in a large number of cement products with high energy consumption and low performance continue to enter the market, and these equipment with low energy efficiency ratio have been running, The specific performance characteristics of large amount of electric energy consumption are as follows:

cement pipes are easy to process, with a wide range of raw materials, low price and long service life, and have been widely used in construction and municipal construction. Cement pipe piles are widely used in the infrastructure of expressways, bridges, house foundations, river embankments and wharfs because of their convenient and fast construction, time-saving and composite material industries, which are small markets, labor-saving, reliable quality and relatively low cost

II Process of cement pipe making

cement pipe pile is one of numerous cement products. It has a variety of production processes. In order to ensure the uniformity and compactness of cement pipe wall thickness, the most common production and processing process is centrifugal forming. Centrifugal forming is to inject the batched concrete into the mold cavity. First, the concrete is mixed at low speed. After mixing evenly, the motor speed rises to medium speed. Under the action of centrifugal force, the concrete is basically formed, and the concrete is gradually compacted. Then, the whole process is completed after high-speed forming and dehydration. The cement pole is also produced by a similar centrifugal casting method, and its production process is basically the same

the centrifugal forming method has high requirements for electrical transmission equipment. First, it requires full load starting, and the starting torque should be more than 100% of the rated torque of the motor; Secondly, the time of low-speed operation is long, and the low-speed torque is required to be large; Finally, due to the large speed regulation range of the pipe making machine, in order to ensure the quality of the cement pipe pile, it is required that the rotating speed is basically stable within the whole working speed range. Early speed regulation methods include mechanical step-by-step speed regulation, commutator motor speed regulation, DC speed regulation, electromagnetic speed regulation, etc. Due to its simple structure, easy use and relatively low price, electromagnetic speed regulation has been widely used in cement pipe making equipment in recent years. However, the efficiency of electromagnetic speed regulation is low. The efficiency is 85% at the highest speed. The lower the speed, the lower the efficiency. The low-speed time of cement pipe centrifugal forming process accounts for about 50%, and the energy consumption is quite large when the electromagnetic speed regulation speed is low

the mechanical characteristic of the load of the cement pipe making machine is a large inertia load. Before starting, it is necessary to add enough concrete of a cement pipe pile in the mold cavity. After starting, it runs at a low speed, which is obviously a heavy load start. When the electromagnetic governor operates at low speed, its mechanical characteristics are soft and its low-speed torque is poor. To ensure the normal production, the capacity of the motor is selected to be large, which further increases the energy consumption. The electric drive of general pipe making machine is driven by a 75kW (55kW) electromagnetic speed regulating motor. The range of speed regulation of the electromagnetic speed regulating motor is limited, and the low-speed torque is poor. However, the torque required for low-speed mixing of concrete is large. If it cannot be met, the speed will be unstable, or even may not be started. The instability of rotating speed has a certain impact on product quality. In addition, the rated speed of 4-pole AC asynchronous motor is 1440r/min, but the electromagnetic governor can only be adjusted to 1200r/min at most. High speed, beneficial to the improvement of cement pipe quality. From the above requirements of the pipe making machine for electrical transmission, the electromagnetic governor used in the shipbuilding industry is a helpless choice. Now the price of the frequency converter has dropped to a reasonable level. The excellent performance of the frequency converter can fully meet the requirements of the pipe making process. It is the best option to use frequency conversion speed regulation instead of electromagnetic speed regulation

III Frequency conversion speed regulation of cement pipe

according to the above situation, the mechanical characteristics of the frequency converter are approximately constant torque, the motor can run at 5Hz, and can reach 1440r/min at high speed 50Hz, with a speed regulation ratio of 1:10, which greatly meets the process requirements of cement pipe making. Dongguan Dalingshan Hongji pipe pile factory has 4 sets of centrifugal pouring machines. The model and power of the motors are y260m-kw and y250m-kw respectively, all of which adopt electromagnetic speed regulation. To transform the electromagnetic speed regulation into variable frequency speed regulation, the simple method is to drive the electromagnetic speed regulation motor with the frequency converter, and adjust the excitation of the cup rotor of the electromagnetic speed regulator to the maximum, as mentioned above, the efficiency is 85%. In order to achieve the highest energy-saving efficiency, the electromagnetic speed regulating motor is replaced and stored, and the data processing after the experiment puts forward higher requirements for ordinary Y-series three-phase squirrel cage motor. Two Senlan sb40s75kw and two bt40s55kw frequency converters are used. The frequency converter is set for external control terminal operation, and the potentiometer adjusts the frequency of the frequency converter. The acceleration and deceleration time settings are relatively long, both of which are 120s. When the speed is reduced to the output frequency of the frequency converter of 5Hz, the DC braking is enabled, which is very convenient to operate. After using the frequency converter, the speed stability is good, and the forming quality of the pipe pile has been greatly improved. After variable frequency speed regulation, considering that the motor runs at low speed for a long time, the heat dissipation of the motor is affected and the temperature will rise. In the process of transformation, when the electromagnetic speed regulating motor is replaced by Y Series AC asynchronous motor, if it is a replacement of equal capacity, the capacity of the original motor is selected to be relatively large, and the temperature rise of the motor after transformation will not exceed the rated value, so it is not necessary to add a constant speed fan for cooling; If it is non equal capacity replacement, and the capacity of the replacement motor is smaller than that of the electromagnetic speed regulating motor, it is necessary to add a constant speed fan on the motor tail cover to facilitate the heat dissipation of the motor

IV Energy saving analysis

the cement pipe making machine adopts 55kW or 75kW electromagnetic speed regulating motor, and the speed is usually controlled at r/min, which controls the motor speed according to the centrifugal pipe making process. It has been proved by practice that the average energy saving by using frequency conversion speed regulation instead of electromagnetic speed regulation is about 50%. Why does the frequency conversion transformation of electromagnetic speed regulation have such a great energy-saving effect? Because the use of electromagnetic speed regulation is an energy consuming and inefficient speed regulation method, such as formula (1) output power of main motor shaft of electromagnetic motor:

p0=t0 × N0 (1)

where:

p0: shaft output power (kw)

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