3 Starter dot is a device whose main function is to start and maintain the speed of the DC bypass motor. The 3-point starter connects the resistor in series with the circuit that reduces the high starting current and therefore protects the machines from damage. Mainly there are three main points or terminals in the 3-point DC motor starter. They are the following
L is known as the line terminal, which is connected to the positive supply.
A is known as the armature terminal and is connected to the armature windings.
F is known as the field terminal and connects to the field terminal windings.
Disadvantages of a 3-point starter
The following drawbacks of a 3-point starter are as follows:
The 3-point starter suffers a serious inconvenience for motors with a large speed variation by adjusting the field rheostat.
To increase the motor speed, the field resistance must be increased. Therefore, the current through the branch field is reduced.
The field current can become very low due to the addition of high strength to obtain a high speed.
A very low field current will cause the clamping electromagnet to be too weak to overcome the force exerted by the spring.
The retaining magnet can release the arm of the starter during normal operation of the motor and therefore disconnect the motor from the line. This is not a desirable action.