3 point & 4 point starters are used
A DC motor is an electric motor that runs on direct current (DC) electricity. A DC motor is designed to run on DC electric power. Two examples of pure DC designs are Michael Faraday's homopolar motor (which is uncommon), and the ball bearing motor, which is (so far) a novelty. By far the most common DC motor types are the brushed and brushless types, which use internal and external commutation respectively to reverse the current in the windings in synchronism with rotation.
permanent magnet motors and series motor
The No volt coil (NVC) and the Overloadrelease(OLR) are the two protecting devices incorporated in DC starters
A shunt DC motor connects the armature and field windings in parallel or shunt with a common D.C. power source. This type of motor has good speed regulation even as the load varies, but does not have the starting torque of a series DC motor
For some equipment it doesn't matter, other types of equipment will be destroyed. For a simple electric heater or an incandescent bulb AC or DC are acceptable, provided the rms voltage of the AC is equal to the DC voltage. If the heater has a time switch, DC is unacceptable. A DC motor may or may not work with AC depending on its type and size. The commutator motor as used in vacuum cleaners is essentially a DC motor, but most types of AC motor are not interchangeable to DC. Electronic circuits usually required a DC supply and if AC is applied many of the components will be destroyed.
In its simplest form, the starter of a dc motor is a variable resistance in series with the armature circuit of dc motor to reduce the high starting current so that the armature winding does not get overheated and burnt while the motor isgetting started. As the rotating armature of dc motor picks up speed, the starter resistance is gradually reduced so that the motor is able to attain its full speed when the starter is not expected to offer any additional resistance in series with the armature winding of the dc motor. At full speed the motor starts running normally, of course, without the help of starter. In other words, the starter offers resistance to armature current during starting of dc motor only. Under normal working condition of dc motor , the starter is electrically out of armature circuit of the motor. The starter protects the armature of dc motor from getting damaged. The electromotive force (emf) induced in the armature winding during starting builds up from zero value to max value to restrict the armature current within the permissible value at full speed. As the speed of armature/motor build up, armature induced emf also starts building thus reducing the role resistance offered by the starter, hence requiring it to gradually reduce as the motor picks up full speed.
Two point starters are often used for motors that do not require frequent starting and stopping, as they are simpler and cheaper than three-point starters. They are suitable for applications where the motor will run continuously once started.
actually dc motors are of several types in which one of them are 1).brushed 2).brushless ...so the motor present in DVD are the brushless dc motors ...
A DC shunt motor is a motor using DC supply with the the inductor connected parallel to the armature.
6V dc motor
There are many types of motors used in industrial applications. The most common would probably be a DC motor, as the motor's speed is easily controllable and well suited for production processes.
A synchronous motor is an ac motor that does not run on dc.