Starters for induction motors

In this article we discuss the various starting methods for induction motors and the need for starters. First the starting principle is discussed along with the types of starting methods. Then the construction and working of the DOL (direct on-line) starter and the Star-Delta starter are shown.

Small three phase induction motors can be started direct-on-line, which means that the rated supply is directly applied to the motor. The starting torque is likely to be 1.

Need of using starters for Induction motor.

Two (Star-Delta and Auto-transformer ) types of starters used for Squirrel cage.

Starter using additional resistance in rotor circuit, for Wound rotor (Slip-ring). YPeS of Starter for 3-Ph InductIon motorS For slip-ring induction motors : Rotor rheostat starter For squirrel cage induction motors : D. StartIng of SlIP rIng InductIon motor In . At the time of starting, the motor slip is unity, and the starting current is very large. It works on the principle of rotating magnetic fiel i. This provides one third of DOL current to the motor, thus reducing the high inrush current inherent with large capacity motors at startup. So the reason of using the starter is clear here.

We use starters in order to limit the high starting current. We use different starters for both the type of three phase induction motors. Let us consider first squirrel cage type of induction motor. A stator is needed for an induction motor (three phase type) in order to limit the starting current.

This exercise covers DOL starters and soft starters , which are two of the most popular types of starters for industrial induction motors. Direct-on-line starters are the simplest type of starter. Among all these types of motors, a few types of motors required to be operated with certain conditions. Solid state soft starters can control one or more phases of the voltage applied to the induction motor with the best . We know that as load increases on the motor current drawn. It provides an advanced method of reducing current during motor starting and stopping.

But for larger motor the starting current may be so high that it may damage the stator coil or even. The different methods of starting an induction motor 1. Series reactor starter Or , A three phase Induction Motor is Self Starting. Abstract: In this paper two-phase soft start control of three-phase induction motor is proposed. The present three-phase soft starter for induction motor is compared with that of proposed two-phase soft starter on the basis of torque fluctuations, starting current demand and starting time of induction motor.

IEEE Transactions on Energy Conversion, Vol. A Solid State Direct On Line Starter For Medium Voltage Induction Motors. With Minimized Current and Torque Pulsations. TUBITAK-Bilten Information Technologies and Electronics Research . The rotor of the Induction motor contains cylindrical core with parallel slots that contain conductors.

Modern starters provide much more than just current limitation. The inrush current in 3-phase induction motors varies from five to seven times the rated current. In some applications, this level of inrush current may cause a . Starters are used to reduce inrush current by applying less voltage in starting.

In starting as slip s= the induced EMF in rotor circuit would be sE2=E hence heavy current flows in short circuit rotor circuit, reflect to draw heavy primary current from stator circuit, or from the mains, and hence may blow out fuses. The main purpose of any starter is to reduce the requirement of high starting current.