Application of CFD Simulation Analysis in Thermal Design of Industrial Generators

A generator is a rotating machine that converts mechanical energy into electrical energy. During the energy conversion process, there is energy loss. For an electric excitation generator, there are mainly the following five losses. The first is the copper loss of the stator, which accounts for about 45% of the total loss. About %; followed by the iron loss of the stator, accounting for about 20%; third, the copper loss of the rotor, accounting for about 20%; then mechanical loss, mainly wind wear loss, accounting for about 10%; and finally the excitation loss , accounting for about 5%.

The losses of the generator are ultimately converted mainly into heat, which is the source of the generator’s heat. The temperature plays a key role in the insulation life. Basically, every 10 degrees increase will affect the insulation life by 1 times. At present, the cooling of industrial generators mainly requires direct contact between the air and the heat source, and the heat is removed through convection heat transfer. This is true regardless of the IC01, IC81W or IC616 cooling methods. Therefore, understanding the distribution of airflow inside the generator is particularly important for the thermal management of the generator. STAMFORD once used a Pitot tube to measure the flow field wind speed in the gap between the stator core and the base, but it was very time-consuming and labor-intensive. Moreover, it is difficult to find a suitable method to measure the airflow distribution in small spaces such as the air gap between the stator and the rotor, near the end coils and between the rotor poles. However, the heat dissipation conditions in these places are very important to the overall heat dissipation of the generator.

We know that simulation calculations based on the thermal path method are very popular in motor thermal design, such as MotorCAD software. However, in order to achieve a certain degree of accuracy in thermal path method simulation analysis, it is necessary to have an accurate understanding of the flow field near each heat dissipation surface in the motor, so that correct parameters can be set in the calculation and accurate results can be obtained. CFD (computational fluid dynamics) simulation technology provides us with a favorable means to explore the airflow distribution in these places.

By analyzing the flow field of a certain IC81W cooling machine, we provide reliable air volume for the cold core design and optimize the best position of the cold core in the water-cooling box. Figure 3 is an analysis of a certain IC01 cooling machine. Combined with experimental data, the temperature distribution of the motor is obtained, which facilitates thermal design and electromagnetic engineers to carry out targeted optimization design. Figure 4 shows the cooling fan of the generator that was analyzed and optimized through CFD simulation. A fan with better performance was successfully designed and the cooling air volume was increased.

CFD simulation technology plays a very important role in the thermal management design of generators. With the help of its analysis results, the best generator thermal management solution can be designed while shortening the product development cycle and reducing the number of prototypes.