2. Advantages of VSD

Variable speed drives:

• improve energy efficiency eg savings in excess of 50% can be achieved
  

• improve power factor and process precision
  

• provide other performance benefits such as soft starting:
  

• less mechanical stress on the system leading to longer life, lower maintenance overhead
  

• reduced voltage drop on start up: so other systems are less affected eg lights don’t dim or other devices shut down.
  

• over speed capability
  

• eliminate the need for expensive and energy wasting throttling mechanisms such as control valves and outlet dampers.

Imagine a situation in which you have 10 motors at 10 amps each starting together on small factory line. The starting currents under various starting methods would be:

• direct-on-line = 1000amps,
  

• soft starters = 200 amps and
  

• VSDs = 100 amps!