A DC machine is an electromagnetic energy alteration device. The working principle of a DC machine is when electric current flows through a coil within a magnetic field, and then the magnetic force generates a torque which rotates the dc motor.
The DC machines are classified into two types such as DC generator as well as DC motor.
The main function of the DC generator is to convert mechanical power to DC electrical power. whereas a DC motor converts DC power to mechanical power.
The AC motor is frequently use in the industrial applications for altering electrical energy to mechanical energy. However, a DC motor is applicable where the good speed regulation & ample range of speeds are necessary like in electric-transaction systems.
A coil of wire with a current running through it generates an electromagnetic field aligned with the center of the coil. The direction and magnitude of the magnetic field produce by the coil can be change with the direction and magnitude of the current flowing through it.
A simple DC motor has a stationary set of magnets in the stator and an armature with one or more winding of insulated wire wrapped around a soft iron core that concentrates the magnetic field. The winding usually have multiple turns around the core, and in large motors there can be several parallel current paths. The ends of the wire winding are connect to a commutator. The commutator allows each armature coil to be energize in turn. And connects the rotating coils with the external power supply through brushes. (Brush-less DC motors have electronics that switch the DC current to each coil on and off and have no brushes.)
Therefore, The total amount of current sent to the coil, the coil’s size.
what it’s wrap around dictate the strength of the electromagnetic field create.
Moreover, The sequence of turning a particular coil on or off dictates what direction the effective electromagnetic fields are point. By turning on and off coils in sequence a rotating magnetic field can be created. These rotating magnetic fields interact with the magnetic fields of the magnets (permanent or electromagnets).
In the stationary part of the motor (stator) to create a torque on the armature which causes it to rotate.
In some DC motor designs the stator fields use electromagnets to create their magnetic fields which allow greater control over the motor.
At high power levels, DC motors are almost always cool using force air.
Different number of stator and armature fields as well as how they are connect provide different inherent speed/torque regulation characteristics. The speed of a DC motor can be control by changing the voltage apply to the armature.
The introduction of variable resistance in the armature circuit or field circuit allowed speed control. Modern DC motors are often controlled by power electronics systems which adjust the voltage. By “chopping” the DC current into on and off cycles which have an effective lower voltage.
Since the series-wound DC motor develops its highest torque at low speed. it is often used in traction applications.
such as electric locomotives, and trams.