When it comes to specifying electric motors for solar photovoltaic tracking applications, environmental protection is a prime consideration due to their exposure to the elements. Motor designs for solar power applications must stand up to extremes in temperature (both absolute and over a broad range), humidity and highly corrosive salt sprays, wind loads, and abrasive airborne particulate matter. Because they are exposed to the elements, motors should be designed to IP65 (protected against dust and water jet spray) or IP67 (protected against dust and effects of immersion in water to a depth between 15 cm and 1 m).
Both the motors and the gearheads attached to them must be optimized for the low speeds and high torque that characterize solar tracking. Gearing considerations include such elements as engineered lubrication, low-friction gear design, and special sealed ball bearing designs, along with appropriate treatment of output shafts and housings. As a complement to this safety system, the gear motor includes an electrical brake that absorbs the effect of the wind on the mobile elements of the tracker, thus avoiding damage and helping to extend the useful life of the machine and its main elements.
Permanent magnet brush dc motors (PMDC) are relatively efficient, easily controllable and, if properly built, can last a long time , despite the brush or commutator wear that is inherent in their design. They also exhibit a wide speed range that is advantageous in stowing situations.