Application of Powtran Technology’s PI500 Series Inverters in Grain Screening Machines-POWTRAN-Engaged in intelligent motor control products

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Application of Powtran Technology’s PI500 Series Inverters in Grain Screening Machines

2020-08-20

I. Preface:

China is a major producer and consumer of grains and oilseeds. For five consecutive years, China’s grain production has remained above 650 million tons, with per capita availability reaching over 470 kilograms—far exceeding the average food security threshold set by the Food and Agriculture Organization of the United Nations. China’s grain reserve policy has consistently favored a conservative and prudent approach. Grain production and processing require a wide range of machinery and equipment, among which grain sorting machines are one important type. The following introduces an application case of using frequency conversion control in rice sorting machines.

2. Equipment Introduction:

The rice production process inevitably generates broken rice. Before bagging, it’s essential to sort out the whole grains of uniform size. This is precisely when a white rice sieve comes into play. Previously, using industrial-frequency motors with fixed speeds made it difficult to control the amount of broken rice in the finished product.

By using a frequency converter, the motor speed can be adjusted to reduce the percentage of broken rice in the finished product when producing different types of rice. This is one of the quality control standards for rice upon出厂. Differences in speed significantly affect the uniformity of the rice and are applicable to various types of rice as well. The attached figure shows an overall view of the rice sorting machine.

3. Inverter Configuration:

When using power-frequency direct starting, the motor can reach its rated frequency at the fastest possible speed, minimizing the likelihood of mechanical collisions or even the screen body jumping off its track. To achieve a start-up performance close to that of direct starting when using a variable-frequency drive (VFD), the acceleration time must be very short, which in turn leads to an increase in the starting current. Therefore, when selecting a VFD, it’s crucial to choose a model two sizes larger than required. This approach helps prevent overcurrent alarms during the start-up phase and ensures the safe and stable operation of the equipment. Based on the specific operating conditions of each piece of equipment, we have equipped every unit with a PI500 7R5G3 VFD.

Meanwhile, based on the startup and operational characteristics of the equipment, we’ve also optimized the parameter settings, with the most significant improvement being the segmented acceleration and deceleration. The acceleration time up to 35 Hz is extremely short; once the screen body has gained sufficient rotational inertia, it can run steadily and maintain stable speed regulation.

4. Precautions for Use:

1. Before starting the equipment, thoroughly inspect the rotating parts and other connection points for any signs of looseness, collisions, or rubbing against each other.

2. After stopping operation, first stop the feed supply. Then continue running the equipment for several more minutes to completely discharge all material from the machine before shutting it down, thus preventing material from accumulating inside the machine.

3. Adjusting the screen mesh must be done after the machine has been stopped. First, loosen the nuts and pressure plates on the screen mesh, then carefully remove the original screen mesh and replace it with the desired one. Finally, reassemble the components in the reverse order of disassembly.

4. During normal production, the feed should be continuous and uniform; both excessively large or small feed rates will affect the process efficiency. During production, strictly prevent blockage at the discharge port, which could lead to a full-screen accident and damage machine components.

5. Effects after adopting the PI500 series variable frequency control solution:

1. During segmented acceleration and deceleration, the system starts smoothly without collisions, thereby greatly enhancing its safety and reliability.

2. After using the frequency converter, workers can adjust the speed according to the rice output quality, minimizing both the amount of broken rice in the finished product and the amount of whole grains mixed with broken rice.

3. After using a frequency converter, the rice output speed is faster, the quality is improved, and the motor receives greater protection.

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