Friends, today in this article we will learn about four point starter. I am going to give information about all these in a very good way. So let’s start.
Four point starter –
This starter is used for those shunt and compound motors where the speed of the motor has to be regulated by the starter itself. There are four points in this starter. There are 3 points L, Z and A and a fourth point N in which the negative wire of the supply line is given as shown in the figure.
In the four point starter, the no-volt coil is not connected in series with the field coil of the motor but is connected in series with the starting resistance (R_{s}) on the side of the direct current supply. The no-volt coil is directly on the side of the main supply so that the OC contacts can be protected in case of short circuit supply.
For this, a protective resistance R is also installed in the series of no-load coil (NC) as shown in the figure. Its purpose is that when NC gets short-circuited while lifting the lever by OC coil, the destructive current from it stops and the coil remains safe. Here also the function of voltage-less coil is same as that of three point starter. The internal connections of the starter are shown in the figure. It also has an overload coil O.C. (over load coil) which short-circuits the no-load coil when the current exceeds a specified value. Usually four point starters are installed with an additional field weakening resistance for speed control.
What did you learn today:-
Now you must have known what four point starter is. You must have got the answer to all these questions very well.
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