Function of 4-Point starter : 4-Point starter is mainly used to prevent the “unscheduled stoppage”. Here the field circuit and the electromagnet are not in series. So, if any reason there is less current flow through the field coil, it will prevent the unscheduled stoppage. The four point starter provides the motor with no voltage protection.If the power fail, the motor must be disconnected from the line. If not, full line voltage will be applied to the armature without the benefit of starting resistor. When power is restored. The holding magnet, being connected across the line, release the arm when the voltage drops below a specific value, thus protecting the motor when power is restored.
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