Question

The most preferred type of starting motor on car

Answer 1

Types of Motor Starters

Direct On line: It consists of simple push button as the controller. When the start button is pressed, the switch connecting the motor and the main supply is closed and the motor gets the supply current. In case of over current, the stop button is pressed and the bypass auxiliary contact is opened.

Star Delta: The 3 windings are first connected in star connection and then after some time (decided by the timer or other controller circuit) the windings are connected in delta connection. In star connection, the current drawn is 0.58% of the normal current and also the phase voltage is reduced to 0.58%. Thus the torque is reduced.

Auto Transformer starter: It consists of an auto transformer (A Transformer with a single winding tapped at different points to supply percentage of it primary voltage across secondary) in star connection, which reduces the voltage applied to the motor terminals. It consists of 3 tapped secondary coils connected to the three phases. In the starting period the transformer allows application of lower voltages to the three windings.

Stator Resistance Starter: It consists of three resistors in series with each phase of the stator windings, which causes a voltage drop across each resistor and as a result a low voltage is applied to each phase.

Rotor Resistance Starter: It consists of 3 resistances connected in series with the rotor windings, thus reducing the rotor current, but increasing the torque.

Application of Star Delta Starter to Control Starting of Induction Motor

The star delta starter is the cheapest among all the starters and is suitable for applications like machine tools, pumps, motor generators etc. A star delta starter can be used in starting an induction motor by using 2 relays as the connector and the timer as the controller. 1 connector is used to provide the mains supply while the other connector controls the connection of motor in star or delta connection.