What is the primary difference in temperature effect on the life expectancy of a DC motor?

The concept of temperature's impact on the life expectancy of a DC motor is grounded in how heat affects the materials and components of the motor. Motor insulation materials, for instance, have a defined thermal rating, and as the operating temperature increases, the electrical and mechanical properties of these materials can significantly degrade.

A total decrease of 50% in life expectancy at just 10°C increase indicates a drastic impact due to elevated temperatures. Heat can cause insulation breakdown, reduced efficiency, and increased friction within the motor, leading to accelerated wear.

This principle is rooted in the Arrhenius equation, which explains that the reaction rates, including degradation processes, tend to double with every increase of approximately 10°C in temperature. Therefore, a 10°C rise could indeed lead to a substantial reduction in lifespan, which aligns with the correct choice about a 50% decrease in total life expectancy.

Overall, the understanding of thermal effects on motor life brings to light the importance of maintaining proper operating conditions to ensure longevity and reliability in electrical systems.