Farm duty motors
require a high-starting torque (for starting under load - in some cases the load cannot be applied after starting, so the motor has to have the capability to start under such conditions; it will get hot before reaching nominal RPM) and a moderated starting current (so the power supply is not overloaded when the motor starts under load). Some other features of this type of motor include reversible rotation, shielded ball bearings, and dustproof. Farm duty motors are continuous duty motors. This means that the motor requires no rest periods, able to function night and day, continuously, for months on end. It has a good cooling fan (a metal or plastic turbine mounted on the shaft at the other end from the load; it is covered by the motor enclosure; most motors cool this way during functioning), large surface cooling fins on the metal enclosure, and windings impregnated with high-temperature varnish. These motors also feature protection cages for fans or other machinery driven by the motor, as usually the users are not technical people and need extra protection. For the same reason overload protection is normally mounted on the motor to avoid remote accidentally starting the motor after a fault. Most motors are able to function in reverse if needed, but a cooling turbine must be built for this in order to allow working in reverse for a long time and have straight blades instead of slanted. Slanted blades would provide a better airflow but only when the motor rotates in a certain direction. Some motors used on farms may require having an Explosion Proof certification (HAZLOC) such as motors used in grain silos or flour mills. Although sounds like a benign operation, when filling a grain silo, for example, theres a lot of fine dust produced that can explode if a certain ratio of air/dust is reached. So the motors (fans
, grain elevators, etc.) must not make sparks, either electrical or mechanical (caused by friction or hitting steel parts).