Electronic starters and variable speed drives

The most common way of starting asynchronous motors is directly on the
line supply. This technique is often suitable for a wide variety of machines.
However, it sometimes brings with it restrictions that can be inconvenient
for some applications, and even incompatible with the functions required
from the machine:
- The inrush current on start-up can interfere with the operation of other
devices connected on the same line supply
- Mechanical shocks during starting that cannot be tolerated by the
machine or may endanger the comfort and safety ofusers
- Acceleration and deceleration cannot be controlled
- Speed cannot be controlled
Starters and variable speed drives are able to counter these problems.
Electronic technology has made them more flexible and has extended their
field of application. However, it is still important to make the right choice.
The purpose of this "Cahier Technique" is to provide more extensive
information about these devices in order to make it easier to define them
when designing equipment or when improving or even replacing a motor
switchgear assembly for control and protection.