A robotic manipulator constructed with a series of links connected by joints has coupled, configuration-variant, and nonlinear dynamic characteristics. There have been several approaches to design conditions to simplify these complex dynamic characteristics. In this article, we examine the energy equation of the robot system and derive general conditions on the link parameters simplifying the energy equation. These conditions are basic conditions by which the physical meaning of the previously proposed design conditions can be interpreted. As a result, we can understand clearly the physical meaning of the robot design conditions and easily obtain the design conditions. With these general conditions, the limitations of the link design in simplifying the robot dynamics are analyzed. Finally, we redesign the PUMA robot as an example and obtain a very simplified robot dynamic equation.