In order to make a correct selection of a VSD unit for an application, the load type and the demand of the driven system needs to be established. The load demand is achieved by changing the speed of the motor driving the system. Motor torque /Speed characteristic are very important, because the motor provides the torque that the load requires and not the VSD.
VSD (Inverter) only provides speed change and the current to drive the motor. So the sizing of the motor to provide power and torque and rated speed is critical. Then based on the selected motor and load type then a VSD can be selected.
Important factors to consider selecting motors:-
This type of load exists when a material is being rolled or wound during which the diameter of the reel changes, but the power needs to be maintained constant.
This type of load is common in paper industry. Combination of constant Power & torque.
Maintain power at above normal base speed
In applications where high torque is required at low speeds.
For other load types the the Torque/Speed relationship has to be defined.