Methods to reduce the starting current of an induction motor

Abstract

An inrush current is produced when an electric load is turned on. For an induction motor this current can reach 5–10 times the full-load current. This transient current can cause issues in large machines attached to weak grid connections. To protect the grid connection this paper explores ways that the starting current can be reduced. Standard starting techniques are reviewed then the starting energy and reactive power requirements are examined by way of example. These illustrate that to some degree the starting current can be reduced with a tuned capacitor bank; however, for better reduction then an energy storage unit is used, such as a battery or a storage capacitor, and this is accessed through a PWM inverter for charging and discharging.