Hello, friends, I hope you all are doing great. In today’s tutorial, we will discuss the Difference Between Three Point & Four Point Starter. The device that used for the starting and running of the motor is called starter. The most commonly used starters are three-point and four-point starters. 3 point starter the no voltage coil is not attached in a series configuration with the field winding but in 4 point starter no voltage windings is linked with the power supply.

The NVC or no voltage coil is a relay that stops the operation of the motor when the input supply is off. In the three-point starter configuration, the NVC is connected in series combination with the field winding so current passing through the NVC and field winding is the same.  In today’s post, we will have detailed look at both three-point and four-point starter with the detailed and compare them to find their differences. So let’s get started with a Difference Between Three-Point & Four Point Starter.

Difference Between Three Point & Four Point Starter

Three-point Starter

• The start that has 3 terminals to operate the motor is called a three-point starter.
• It employed in shunt and compound dc motors.
• It called three points starter since it consists of three pints denoted as L, F and A
• L points of these modules is linked to any terminal of the battery.
• A point is linked with the armature windings

• The 3 terminals of the three-point starter are Armature, field winding terminal, and the Line terminal.
• The connection between NVC and field is series.
• Its disadvantage is that bear serious problem related to speed control of the motor.
• To get the normal speed of moto there should be a reduction in field current
• it consists of an overload release coil that works in the sense that if the motor armature current is large then the field has such value to attract the M point.
• In case of there is cut-off in supply then its HC will become de-energized and off the pointer of start.
• That helps the motor to save in case of supply is recovering

Working Principle of Three Point Starter

• The working operation of three point starter discuss here

• At start dc power is get on and handle is in off state
• Now move the handle first stud when it there is connection made between stud and handle total starting resistance is added in series combination to the armature winding and shunt windings is linked about the dc supply.
• Then slowly move handle to last stud starting resistance is eliminated from the armature. When handle reaches to last stud handle control through magnetically through NVC that get energized through shunt field current,
• In case of open circuit and open filed circuit NVC get de-energized and handles move back to Off state.
• If NVC not in use when supply is not connected in results handle make connection to last stud.
• If supply is connected again the motor will directly linked about the complete supply volts causes in high armature current and can damage the motor
• If motor is overloaded it will get high current. This high current will rise the MMF of OLC and apply force at the plunger that results in short circuit of NVC.
• In results NVC is de energized and the handle in off state through control spring. Motor is separated from the power supply.

Four Point Starter

• The starter that has 4 terminals to operates the motor is called a four-point starter.
• It makes a parallel connection to the field winding of the motor
• It can be employed to such motor that has varaibel speed.

• The four terminals of 4 point starters are Armature, Field winding terminal, Line, and extra terminal which directly link input supply with the (NVC).
• The NVC is attached to the field winding in parallel combination.

That is a detailed post about the difference between a three-point starter and four-point starter. If you have any query ask in comments. Thanks for reading. Have a good day