Construction of 3 Point Starter

What is a Three-Point Starter?

An electrical device known as a three-point starter is used to start and maintain the speed of a DC shunt motor. The connection of resistance in this circuit is in series which decreases the initial high current and protects the equipment against any electrical failures. Here, the event of back e.m.f plays an essential part in operating the motor. This EMF extends when the motor’s armature begins to rotate in the magnetic field by acting against the voltage supply....

Construction of 3 Point Starter

Construction wise a starter is a variable resistance, integrated into the number of sections as shown in the figure close to. These sections’ contact points, designated OFF, 1, 2, 3, 4, 5, and RUN, are referred to as studs. Apart from these, there are three primary points, commonly known as...

Working of Three Point Starter

In above we discussed about construction, let us now discuss into the working of the 3 point starter. Initially, the handle is set to the OFF position when the power is supplied to the DC motor. Then handle is gradually moved against the spring force to connect with stud No. 1. As of now, field winding of the shunt or the compound motor helps supply through the parallel path given to starting resistance, through No Voltage Coil. whereas the entire initial resistance is connected to the armature in series. The high starting armature current subsequently gets limited as the current equation at this stage becomes:...

Functions of No-volt Release

At the point when the motor reaches at the normal speed and the arm is reached at the ON position, the entire starting resistance is cut off from the circuit. Now in running condition, assuming that the supply is interrupted or disconnected, the starting arm remains at the ON position. Additionally, the armature winding is connected directly across the primary supply when the supply is restored, so there is no back EMF in the circuit....

Functions of Over-load Release

To prevent overloading, a second overload release device is connected in series to the motor. The overload release receives the same amount of current as the motor because this device is connected in series with it....

Uses of Arc

We know that arc provides supply to the NVC and field winding. Also, without an arc, we can supply current by directly connecting across the first resistance i.e., to the terminal-1, as shown by a dotted line. Be that as it may, when the handle is moved to the ON position. The whole resistance which is connected in the armature circuit during starting will comes under the field circuit. This increase in field resistance will influence its performance....

Comparison between 3-Point Starter and 4-Point Starter

FEATURES 3-POINT STARTER 4-POINT STARTER Terminals It has three terminals they are supply, armature, and field It has four terminals they are supply, armature, and two field Cost It is low cost It is high cost compared to 3-point starter Starting Torque It has less starting torque It has high starting torque Durability It has a less durable compared to four point starter It has a high durable Size Smaller in size Larger in size Power Factor It provides the low power factor It provides the high power factor Applications It is used in compound and shunt motor It is compatible with a motor that offers adjustable speed...

Advantages of 3-Point Starter

A 3-point starter is used with DC shunt motors. The three-point starter aids in motor speed control. This starter can be also used in machine processing plants and spinning factories. It reduces the high starting current. A three-point starter protects the motor from short-circuits and over-load issues....

Disadvantages of 3-Point Starter

The primary disadvantage of 3 point starter motor is, that it is a huge variation of speed by adjustment of the field rheostat. This starter isn’t suitable for variable-speed motors. While increasing the high resistance from accomplish a high speed, the field current will always be extremely low. Large field current adjustments are not suitable with 3-point starters. The holding electromagnet will not have the option to persevere through the power of the spring on the off chance that the field current is generally low. At a low field current, the NVC fails to keep the handle in the ON position, which would disconnect the motor from the supply. This magnet can disengage the H handle from the power source and delivery its arm by means of the typical engine capability. The 4-point starter can therefore be utilized when there is no associated volt trip coil in the parallel field. The field winding doesn’t have additional opposition in series, so speed regulation isn’t possibilities. Because there is no additional resistance to protect against faults, the condition circuit may become damaged....

Applications of 3-Point Starter

A 3-point starter is a type of starter that’s commonly used to control DC motors. It’s mainly used in situations where precise control over motor speed and torque is necessary. Given Below Are Some Applications of 3-Point Starter....

Conclusion

The 3-point starter is a fundamental part in electrical designing, playing a vital role across a great many applications. It drives the pinion wheels of modern apparatus as well as impels electric trains forward. This starter’s viability in directing DC engines has established its persevering through pertinence in different areas, including assembling, transportation, and heavy-duty machinery....

FAQs on 3-Point Starter

1. What is a three-point starter?...