The Micro Series drives are capable of 0-120Hz, SM & SM-Plus O-240Hz, but the speed range possible is limited primarily by application and motor considerations. Please see our 1050 Stock catalog for approximate speed ranges. The high end of the speed range is limited by several factors including the maximum safe speed of the driven equipment and the ability of the motor to spin at that speed without having any mechanical problems like excessive vibration, premature bearing failure, or flying apart. It is also important to note that the torque is no longer constant above its nameplated speed, so torque begins to drop off as you overspeed the motor. At the lower end, the limitation is primarily related to thermal considerations of each individual motor design. Since a motor's fan will be spinning at a slower speed, it will be much less effective at maintaining a motor winding temperature that is acceptable for its insulation class rating. This means that without some other means of external cooling, (like a blower kit) motor life could be severely reduced.