Why do we use 3 point starter in DC shunt motor?
A three-point starter is an electrical device, used for starting as well as maintaining the DC shunt motor speed. The connection of resistance in this circuit is in series which decreases the initial high current and guards the equipment against any electrical failures.
Which starter used for DC shunt motor?
A 4 point starter is used to start and control the speed of a Dc shunt motor with field weakening control.
Why a DC motor starter is called 3 Point starter?
3 point starter is used for shunt and compound dc motor. it is called a three-point starter because it has three terminals named L, F, and A. Terminal A must be connected to the one of motor armature terminal and F terminal to the shunt field terminal of the motor (any of two field terminals).
What is the difference between 3 point starter and 4 point starter of a DC shunt motor?
The most significant difference between the three point and the four-point starter is that in three-point starter the no voltage coil (NVC) is connected in series with the field winding whereas in four-point starter the NVC is directly connected to the supply voltage.
What is the advantage of 3 point starter?
3 Point Starter is a device whose main function is starting and maintaining the speed of the DC shunt motor. The 3 point starter connects the resistance in series with the circuit which reduces the high starting current and hence protects the machines from damage.
How does a 3 point starter works?
A 3 point starter is a device that helps in the starting and running of a DC shunt motor or compound wound DC motor (similar to a 4 point starter). The back emf develops as the motor armature starts to rotate in presence of the magnetic field, by generating action and counters the supply voltage.
What is DC starter?
Starters are used to protect DC motors from damage that can be caused by very high current and torque during startup. They do this by providing external resistance to the motor, which is connected in series to the motor’s armature winding and restricts the current to an acceptable level.
Why do we use 2 point starter in DC motor?
Two point starter is used in series motors because in case of series motor, the armature winding and field winding are connected in series. Therefore series motor achieves dangerous high speed. Therefore inrush of high starting current to the series motor is reduced.
How does a 3 point starter work?
Working of Three Point Starter 1. At this point, field winding of the shunt or the compound motor gets supply through the parallel path provided to starting the resistance, through No Voltage Coil. While entire starting resistance comes in series with the armature.
Where three point starter is suitable for?
The back emf (Eb) is developed as motor armature starts to rotate in presence of magnetic field. Initially back emf is zero, starting current is high. To limit this starting current, we use starter. A three-point starter helps in starting and running the shunt wound motor or compound wound DC motor.
Which is better 3 point starter or 4 point starter?
Four point starter works as a current controlling device in the deficiency of back EMF while starts running of the DC motor. A four-point starter also works as a protecting device. The main difference between a 4 point starter compared to a 3 point starter is, the holding coil is detached from the shunt-field circuit.
What is the use of 3 point starter?
Why do you need a 3 point starter for a DC motor?
A 3 point starter is a device that helps in the starting and running of a DC shunt motor or compound wound DC motor. Now the question arises that why these DC motors requires the assistance of the starter. It is because of Back EMF, it plays an important role.
Which is the line terminal on a DC shunt?
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 is connected to the field terminal windings. The 3 Point DC Shunt Motor starter is shown in the figure below:
What are the terminals of a 3 point starter?
Mainly there are three main points or terminals in 3 point starter of the DC motor. They are as follows: L is known as the Line terminal, which is connected to the positive supply.
What are the drawbacks of a 3 point starter?
Thus, to stop the motor, the main switch of the motor should be opened. The 3 point starter suffers from a serious drawback for motors with a large variation of speed by adjustment of the field rheostat. To increase the speed of the motor, the field resistance should be increased. Therefore, the current through the shunt field is reduced.
