Thermal management is an important design element of all electrical systems because it is directly related to the long-term reliability and life of the system.
If the electrical system overheats, major components will begin to fail, causing the system to fail instantaneously. For example, IGBT chip overheating caused by local overheating, undercooling or overload may cause direct semiconductor damage.
In the long run, material decomposition is related to excessive temperature and will fail at some point. Materials tend to become brittle because high temperatures speed up the cross-linking of the materials, thus losing all the flexibility of typical plastic materials. High-performance busbars use PET (polyester) insulation rated at 105 ° C, which has a long service life (25 years at 80 ° C) for typical traction applications. For ultra-long life or high temperature applications, Thermal insulation materials of 130℃ (at 100℃ temperature, can be used for 40 years).
Although the bus bar generally performs better than all other components of the inverter throughout its life, insulation brittle/cracking is the most common failure during long life, depending on operating conditions, which can result in electrical breakdown and system failure.
In order to evaluate the service life of busbars, it is important to understand the proportion of time required for each temperature during operation. Knowing the maximum temperature alone does not accurately determine the life of the busbar. The maximum hot spot temperature is a common result of ambient temperature and heating of components.
Because the power density (loss) is very low and the conductor has very high thermal conductivity, the heat conduction Rcond does not determine the total thermal resistance Rthe.
1. The heat conduction in the bus bar cannot determine the thermal performance, but is related to the ultra-low power loss density and high thermal conductivity of copper/aluminum.
2. For heat transfer from the device (bus bar) to the environment, radiation is an important contributor (40%) if natural convection is used, second only to natural convection (60%). The insulation of the exclusive surface (lamination) of the bus has a great influence on component temperature.
Post time: Mar-29-2022