Softstarter device and method for an electric motor

摘要

The invention refers to a self adapting soft starter device and a method to control the softstarting of an electric motor. The self-adapting soft starter device (1) comprises an electric current limiting means (2,4,S11) adapted to limit the electric current supplied to the motor (M) to a preset maximum current limit, a ramp-up time determination means (3A,3B,4) adapted to determine the actual ramp-up time of the electric motor (M), a storing means (6,4,S10) adapted to store a preset minimum ramp-up time, a comparing means (4,S17,S21) adapted to compare the determined actual ramp-up time with said preset reference ramp-up time, a replacing means (4,S18,S22) adapted to replace said preset maximum current limit with an auto-adapted current limit based upon the outcome of the comparison between the determined actual ramp-up time and the said preset reference ramp-up time. The soft-starter therefore automatically optimizes the maximum current limit driven by the motor to match its load requirements. This is particularly useful to cater for load variations with time during the lifetime of the product in the application, as it avoids the need of any human intervention to change the soft-starter settings. This auto-adaptation also extends motor lifetime by reducing wear and tear.