The introduction of dc motors and an electrical grid system to run machinery starting in the 1870s started a new second industrial revolution. The 4 point starter has a lot of constructional and functional similarity to a 3 point starter but this special device has an additional point and coil in its construction as the name suggests.
Starting Methods To Limit Starting Current And Torque Of Dc
Dc motor starter diagram. Now the question is why these types of dc motors require the assistance of the starter in the first place. Figure 1 is a typical wiring diagram for a three phase magnetic motor starter. A 3 point starter is a device that helps in the starting and running of a dc shunt motor or compound wound dc motor similar to a 4 point starter. This type of starter can be used for shunt and compound motors and if the field is lost the starter drops out protecting the motor against runaway. A starter is not necessary for a 6v or 12 v dc motor and it can be run directly. Dc motor starters to avoid the above dangers while starting a dc motor it is necessary to limit the starting current.
The primary issue is that dc motors require a large potentially damaging starting current which must be limited by the starter itself. The electromagnet that holds the starter in the run position is in the field circuit. So a dc motor is started by using a starter. Typical line or schematic diagram. If you have a 120v coil instead of running a line from coil overload l2 you must run coil overload neutral. A brushed dc electric motor is an internally commutated electric motor designed to be run from a direct current power source.
Working principle of 4 point starter. Starting a dc motor poses unique challenges. Dc motor starters allow a dc motor or motor controlled device to be turned on or off. This article discusses the construction and working principle of a 4 point dc motor starter. Well its due to the presence of back emf e b which plays a critical role in governing the operation of the motor. Knowledge of basic single and three phase electrical systems including basic ac and dc motor control and safety measures on electrical equipment.
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 motor. There are various types of dc motor starters such as 3 point starter 4 point starter no load release coil starter thyristor controller starter etc. A dc motor starter includes external resistance no volt release coil and overload release coil. Three point manual dc motor starter circuit diagram. The dc motor was the mainstay of electric traction drives on both electric and diesel electric locomotives street carstrams and diesel electric drilling rigs for many years. Brushed motors were the first commercially important application of electric power to driving mechanical energy and dc distribution systems were used for more than 100 years to operate motors in commercial and industrial buildings.
This starter is a so called three point starter. Line voltage control three phase 3ph motor starter controlling a three phase motor rev 08 aug 2006 the above wiring diagram assumes your magnetic starter has a 240v coil.
Gallery of Dc Motor Starter Diagram
