The machine tool controls shut down and some lose their program when a voltage sag occurs. A typical plant experiences about 30 events like this per year. The time needed to restart the machine and the value of scrap materials that are produced can be very large. If the CNC controller does not continue to operate in a minor sag event, the entire machine will shut down. DC drives are used in many industrial processes, including printing presses and plastics manufacturing.
Plastic extrusion is a typical application where voltage sags can be particularly disruptive.
During a voltage sag, the controls to DC drives and winders may trip. These extrusion operations are usually completely automated and an interruption may involve expensive cleanup and restarting requirements. A typical plant may experience 20 to 25 such events per year. Another issue to be considered is that noise from variable frequency drives can disrupt PLC communications. Delivering a power conditioning solution to the plant floor is significantly more complicated than to the data processing center for several reasons.