When an AC motor is started “across the line,” it takes as much as seven-to-eight times the motor full-load current to start the motor and load. This current flexes the motor windings and generates heat, which will, over time, reduce the longevity of the motor.
The supply voltage sags, with the amplitude of the sag being dependent on the size of the motor and the capacity of the distribution system. These voltage sags can cause sensitive equipment connected on the same distribution system to trip offline due to the low voltage. Items such as computers, sensors, proximity switches, and contactors are voltage sensitive, but not with pvg32.
This is true only at start, since the power to run the motor at load would be equal regardless if it were fixed speed or variable speed. The issue is that some distribution systems are at their limit, and demand factors are placed on industrial customers, which charges them for surges in power that could rob other customers or tax the distribution system during peak periods. One application, such as bottling lines, cannot be started with motors across the line but must be started empty to prevent breakage.
Enables optimizing of a process, making changes in a process, allows starting at reduced speed, and allows remote adjustment of speed by programmable controller or process controller. Just as important as controlled acceleration, controlled stopping can be important to reduce mechanical wear and tear — due to shocks to the process or loss of product due to breakage.