Design of high-voltage insulation parts for new energy electric drive systems

Combined with the previous analysis, I wonder if you can judge the superiority of the above five materials in oil resistance and aging resistance?

Having said so much, what material should be chosen for the insulating structural parts of the electric drive system?

This is the question I was thinking about when I was working on insulating parts. As for the answer to this question, we will use the most common physical failure mode of high-voltage insulating parts in electric drive systems - cracking - to illustrate.

The intuitive understanding of cracking is that the material is too brittle (small elongation at break), which is easy to occur under temperature changes and high stress. Therefore, the brittleness of the material is a parameter that needs to be focused on during the design and selection of the insulation structure.

As mentioned before, nylon is naturally superior to aromatic materials in terms of toughness. Considering brittle failure, can we not use aromatic materials?

But we mentioned earlier that nylon’s thermal stability is inherently inferior to that of aromatic materials. Considering aging and failure, does that mean we can’t use nylon anymore?

This analogy may be a bit extreme, but the answer to the previous question comes naturally.

When the material cannot be changed, reasonable structural design can avoid the shortcomings of the material itself.

When the structure cannot be adjusted, reasonable material selection can avoid design deficiencies.

Selection and design are a mutual work. But one thing we need to pay attention to is that there are no materials that cannot be used, only bad engineers.

From this perspective, it is very difficult to become an excellent engineer. You need to have rich industry experience and understand both design and materials. This is probably impossible to achieve in a short period of time, but this should also be our goal.

In actual work, we have also encountered cracking of parts with good toughness and parts with poor toughness. There are many solutions, such as increasing the thickness is a good choice, of course, replacing a material with better toughness is also a common quick solution.

High voltage insulation design standards

Next, let's talk about the high-voltage insulation design standards, which are the parameter limits mentioned above.

Regarding electrical clearance and creepage clearance, the WeChat public account "Choupijiang Laboratory" has systematically collected the existing national/industry standards in: Interpretation and expansion of new energy electric drive system standards: electrical clearance and creepage distance. You can refer to it. However, it should be noted that the limit values ​​in these standards are not hard indicators, but references.

Some parameters can be easily limited according to system conditions, such as the requirements for material tensile strength based on CAE analysis and material HDT based on the system maximum temperature. But what about parameters such as volume resistivity, dielectric strength, and elongation at break?

Back to the previous discussion on material brittleness, brittle materials can lead to cracking, but brittleness is just a characteristic. How brittle will lead to failure? For the same category, PPS can improve toughness by adding additives, while PPA may also reduce toughness after adding additives, so how can we judge?

Summarize

The development of high-voltage and lightweight electric drive systems provides opportunities for the application of plastic materials. As practitioners of electric drive systems, we also clearly feel that plastics are getting closer and closer to us. But objectively speaking, this market is still chaotic and not as mature as the development of plastics in traditional fields.