There are different types of manual starters available for DC motor namely 2 point starter, 3 point starter, and 4 point starter. A DC motor starter includes external resistance, no-volt release coil, and overload release coil. This article discusses the construction and working. A 4 point starter protects the armature of a DC shunt motor or compound wound DC motor against the initially high starting current of the DC. PDF | Direct Current Motors have been used since the early 20 th century shows the schematic diagram of a 4 Point Starter of a DC Motor.
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Let us now look into the construction and working of three point starter to . The 4 point starter like in the case of a 3 point starter also acts as a protective device. 3 4 Point Starter - Download as PDF File .pdf), Text File .txt) or read online. DC motor. 3 Point or 4 Point Starter - Download as Word Doc .doc), PDF File .pdf), Text File .txt) or read online.
The three-point starter also provides protection against an open-field circuit which is not at all provided by the four point starter. Therefore we can say any change in the field current does not affect the performance of the NVC.
The three-point starter also provides protection against an open-field circuit which is not at all provided by the four-point starter.
But we can say the main difference between a 3-point starter and a 4-point starter is the manner in which no-volt release coil is connected.
And thus it does not protect the motor from field failure conditions which result into the high speeding of the motor. Meerut U. This is called high speeding action of the motor. With respect to the figure. Now we are going to discuss about the constructional details of this 4 point starter. Thus field winding gets supply through the parallel path provided to starting resistance with the help of NVC. So it will always maintain the handle in the run position. The basic difference between three point and four pint starter is the connection of NVC.
Total supply current is not passing through the field winding because a parallel resistance connected across the field winding. With the help of 3-coil starter D. Terminals a1a2 will become short circuit across the NVC coil. OCC open circuit coil connected across the field winding of the motor. Due to this high current OLC coil energies. Armature terminals A1A2.
So that motor not runs very high speed in the case of open field winding. If the short circuit occurs across the field winding then very high current flow through the field winding. If this theory successful then we can solve a very big drawback of 4-point starter.
It modify the draw back of 4.
But this resistance having a very high value. Terminal f1 is connected to NVC no voltage coil. Thus field winding gets energies by passing the current. Thus the working of the 3. Fifth edition. Coil starter remove this drawback of 4.
Coil starter remove the problem of 3. When field winding will open circuit the total supply current pass through the OCC coil.
Field winding terminals F1F2.
Terminal a1a2 will become short circuit when OLC coil operated. R4 extra resistance connected in series with armature in staring of D. Field winding connected in parallel across the OCC coil. These explain as: Drawback in 4.
Second edition. So that OCC coil will energies.. I finalize that with the help of 3. A1 is connected to the last resistance terminals. I will try to that it will practically possible or not in lab. Seventh edition. Working of 3-coil starterAs we provide the D. It has three coils.
Due to energies OCC terminal a1a2 short circuit. So that no current flow through the NVC coil. Flag for inappropriate content. Related titles. Jump to Page. Search inside document. This back emf of dc motor is given by and has a major role to play in case of the starting of dc motor. Documents Similar To 3 4 Point Starter. Tanvi Khurana. Mohammed Faizan. Salman Muneer Ahmed. Ali Ahmad. Janmejaya Mishra. Pradeep Rajasekeran.
MAr Lon Dela Cruz. Sudeepa Herath. Tapas Maji. Bandaru Srinivas Babu. Because of the three terminals, the starter is named as the three-point starter. The starter consists two protective devices, i.
The overvoltage coil consists the armature current. When the value of current increases from the limited value then the OLC closes the contact.
Definition of Four Point Starter The connection diagram of the three-point starter is shown in the figure below. The construction of the three-point starter is similar to the four-point starter. The only difference in their construction is that the holding coil is disconnected from the field winding and is directly connected to the line terminal along with the current limiting resistor R in series. Key Differences Between the Three-point and Four-point Starter The starter which consists three terminals is known as the three-point starter.
The four-point starter consists four terminals and hence called the four-point starter. The armature, field and line are the terminals of the three-point starter. Whereas in four-point starter along with the armature, field and line terminal one additional terminal is added which connected the no voltage coil parallel with the shunt field winding.
In the three-point starter, the no-voltage coil NVC is connected in series with the field winding. Whereas in four-point starter the no-voltage winding is connected in parallel with the field winding.