Difference Between Three Point & Four Point Starter

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 is used for the starting and running of the motor is called the 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 the current passing through the NVC and field winding is the same.  In today’s post, we will have a detailed look at both three-point and four-point starters 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 is employed in shunt and compound dc motors.
• It is 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, the field winding terminal, and the Line terminal.
• The connection between NVC and field is a series.
• Its disadvantage is that bear serious problem related to the 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 the three-point starter is discussed here

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

Four Point Starter

• The starter that has 4 terminals to operate 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 a motor that has variable speed.

• The four terminals of 4-point starters are the 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 a parallel combination.

Construction of 4-point Starter:

The 4-point starter is used for restriction of current when dc shunt motor starts and protects armature. The 4-point starter structure is larger in size than the point starter.

The 4-point starter comes with  NVC about supply over protective resistance.

The working of 4 point starter is as

• The terminal of L is used as line or positive supply.
• Armature terminal A is/
• F is the area terminal and N is no voltage coil

 Three Point vs Four Point Starter

3 Point Starter

• The 3 point starter is a circuit that comes with 3 terminals for providing power to the motor
• It has 3 point connection
• It connected in series with field winding
• It is not best for different-speed motors
• Its main connections are Field terminal, line terminal, and armature terminal.
• It is part of compound and shunt dc motors.

4 Point Starter

• This starter circuit comes with 4 terminals and provides power to the motor
• It has a parallel combination with motor field winding.
• It has features to operate with different motor speeds.
• Its main terminals are the Field terminal, Line terminal, Armature terminal, and no voltage coil directly (NVC).

FAQs

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