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.
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.
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