VSD or Soft starter for Stone Crushing Machine Motors

Stone Crushing Machine Motors required high starting torque at the time of starting the motor. It is not required all the time this motors are the short time duty cycle, so Soft starter only limit the starting current to motor. The torque Compensation or the Torque Boosting function is absent in the Soft Starter.

In the VSD, The automatic torque compensation function is present it automatically adjust the torque during the Starting of the motor according to the application in which motor is being used. It provides the current according to the application for which motor is designed
VSDs are less efficient than soft starters, so cost more to run (3% versus 0.5% losses).
VSDs only save energy if they reduce losses in the driven load by operating part of the time at reduced speed. At constant full speed operation, they are less efficient.
The only other reason to use a VSD over a soft starter, is to reduce the start current considerably. This can be of value where there is a very limited supply.

The decision between variable speed drive, Soft starter and electromechanical starter depends on many factors, such as
*Need to start on full load- If required, Soft starter may have problems.
*Frequency of start stop- If not very frequent, Soft starter & VSD does not have much benefit over electromechanical starter, which give soft start and reduce starting current/ stating losses.
*Need to vary speed: If required, VSD is the only solution. Generally speed variation is not necessary for crushers.
* Power of drive, fault level of power supply and cost budget also influence the decision.
* A VSD can provide the best performance (Soft start, Speed control, high torque) but costs the most among the 3 options.