<Li> As the motor picks up speed counter-emf is built up; the arm is moved slowly to short . </Li> <P> The four - point starter eliminates the drawback of the three - point starter . In addition to the same three points that were in use with the three - point starter, the other side of the line, L1, is the fourth point brought to the starter when the arm is moved from the "Off" position . The coil of the holding magnet is connected across the line . The holding magnet and starting resistors function identical as in the three - point starter . </P> <Ul> <Li> The possibility of accidentally opening the field circuit is quite remote . The four - point starter provides the no - voltage protection to the motor . If the power fails, the motor is disconnected from the line . </Li> </Ul> <Li> The possibility of accidentally opening the field circuit is quite remote . The four - point starter provides the no - voltage protection to the motor . If the power fails, the motor is disconnected from the line . </Li>

What are the three common types of winding of dc motor