Application of Excel tools in the design of mechanical loads

1. Preface

Mechanical load is an important test item in the solar module test standard IEC61215, especially under the increasing cost pressure, the mechanical load tester provides an effective means for the material selection of solar module designers to design cost-effective module products.

The cylinder type mechanical load equipment developed by Zealwe Tech solves the problem of overshoot in static testing through perturbation theory and the consistency problem in dynamic testing through PID control technology, which is favored by customers and applied in dynamic and static testing.

The force of the cylinder load is realized through the gas added to the cylinder, the choice of cylinder, the choice of pressure control valve, the choice and layout of the gas pipeline, the size of the gas volume, etc. will affect the uniformity between the cylinders and the pressure control accuracy of the entire surface.

This paper takes the gas flow as an example, and applies EXCEL tool in the design to make the equipment design become simple.

2. Calculation of gas volume

2.1 Calculation conditions

The dynamic load test determines the gas demand. We make the following assumptions.

? Component area: 2.6m*1.4m;

? Cylinder diameter: 32mm.

? Piston diameter: 12mm.

? Cylinder stroke: 300mm.

? Pressure: 1000Pa.

? Inflating time 1 sec.

? Assume that the temperature of the gas does not change after it passes through the flow valve.

? Gas supply pressure is 0.6MPa

? Negligible amount of gas between the flow valve and the cylinder.

2.2 Calculation methods

2.2.1 Downward pressure air volume

The total force for 1000Pa is: 1000*2.6*1.4=3640N;

The force of single cylinder is: 3640/72=50.5N;

The air pressure required for single cylinder pressure is: 50.5/((32/2000)*(32/2000)*3.14)=62893Pa;

The required air volume is: (300/1000)* (32/2000)*(32/2000)*3.14=0.0002412m3;

The air flow rate is: 0.0002412/1 = 0.0002412m3/s = 0.014469m3/min;

The total demand for 72 cylinders is: 72*0.014469=1.04178m3/min.

To simplify the problem, we directly calculate the air supply using the Crabron equation, which is: 1.04178*62893/600000=0.105m/min.

2.2.2 Pull-up air volume

The total force of 1000Pa is: 1000*2.6*1.4=3640N;

The force of single cylinder is: 3640/72=50.5N;

The air pressure required for single cylinder pulling force is: 50.5/((32/2000)*(32/2000)*3.14-(12/2000)*(12/2000)*3.14)=73184 Pa

The demanded gas volume is: (300/1000)* ((32/2000)*(32/2000)*3.14-(12/2000)*(12/2000)*3.14)=0.00020724m3.

The air flow rate is: 0.000207/1=0.000207m3/s=0.012434m3/min.

The total demand for 72 cylinders is: 72*0.012434=0.89528m3/min.

To simplify the problem, we directly calculate the air supply using the Crabron equation, which is: 0.89528*73184/600000=0.105m3/min.

2.3 Conversion in Excel

We enter the above variables and formulas into an Excel sheet as shown below.

We change any variable in the table, can quickly to the gas volume, and this gas volume as the whole system selection and design basis.

However, in the process of practical application, we found that the air volume of 0.105m3/min can not meet the requirement of 1 second inflation, which is caused by pipe resistance, air leakage rate and other influencing factors.

According to the test results, 0.220m3/min air volume can meet the requirements, as a simple treatment, we added a factor of 2.1. Make the design more accurate. Of course, if we change the structural design later, the coefficient of 2.1 can not meet the requirements, we can add more coefficients, and then go to test to verify the accuracy of the formula.

3. Conclusion

This paper describes a method of applying Excel tools to the design of mechanical loads. Through the application of Excel formula, for any variable of design input, we can quickly get the key data of design output as the basis of our design.

Of course, in the actual equipment, due to the pipe resistance, air leakage rate and other circumstances, the ideal formula can not meet the requirements, we can increase the optimization coefficient, so that the formula is more accurate, the design is more accurate and efficient.

Author's Profile

Qian Wensheng

Shanghai Chunshen Pyramid Talent

Focused on the mechanical design and optimization of photovoltaic testing equipment for nearly 10 years. I have led the mechanical design, assembly and commissioning, and process optimization of a series of PV module physical property testing equipment (including breakage tester, hail impact tester, peeling strength tester, lead end durability testing equipment and mechanical load testing system)!

In the future, I will continue to devote myself to improving the reliability and testing accuracy of testing equipment, providing customers with more accurate and efficient testing solutions by continuously optimizing the performance of the equipment, and helping to improve the quality control level of the photovoltaic industry.