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 three-point starter discuss 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 last stud starting resistance is eliminated from the armature. When the handle reaches to last stud handle control through 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 that results in 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 such motor that has variable 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 a parallel combination.
Three Point vs Four Point Starter
| Three-Point Starter | Four-Point Starter | |
|---|---|---|
| Terminals | it has the terminals that are supply, armature, and field | It has four terminals supply, armature, and two field |
| Armature and field connection | It has a series of connection | it comes with a Parallel connection with resistance |
| Starting current | its curent slowly increases | Its current increases more smoothly |
| Efficiency | It is less efficient than the four-point starter | it is more efficient |
| Cost | IT less expensive | it is a costly starter |
| Applications | It used for smaller motors | It used in later motors |
| Speed control | it has limited speed control options | it comes with speed control options |
| Starting torque | it has less starting torque | It has a high starting torque |
| Maintenance | Is maintenance is simple and easy | It is complicated and needs more maintenance |
| Durability | It is a less durable four-point starter | it is highly durable |
| Size | Its size is smaller in size | it comes in a Larger size |
| Motor protection | it need limited motor protection | it provides the Better motor protection |
| Complexity | It is less complicated | it comes within More complex structure |
| Control mechanism | It has an easy control mechanism | it comes with the complex control mechanism |
| Voltage drop | It has high voltage loss | it has less voltage loss |
| Power factor | it provides the low power factor | it has a high power factor |
| Starting time | its starting time is longer | It has a shorter starting time |
| Motor speed range | it is a Narrow speed range | it has a Wider speed range |
FAQs
| Question | Answer |
|---|---|
| Which starter is more efficient 3 point start or a four-point starter? | The four-point starter is more efficient since it provides a smooth start with gradual increases in field current |
| Which starter is more expensive 3 point start or a four-point starter? | The four-point starter is costly since it has a complicated structure and |
| Which starter is used for smaller motors? | The three-point starter is used for small-size motors and 4 point starter is used for larger motors |
| Which starter offers better motor protection 3 point start or a four-point starter? | The four-point starter has god motor protection since it complex control mechanism and feature to limit the starting curent |
| Which starter has a wider speed range 3 point start or a four-point starte? | The four-point starter provides different speed ranges then 4 point starter |
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
