Image courtesy of GSU. DC motor electric current electrical energy magnets mechanical energy. About Author Bobby. March 16, 0.
March 9, 0. March 4, 0. This constant reversal essentially turns the battery's DC power supply into alternating current, allowing the armature to experience torque in the right direction at the right time to keep it spinning.
View an animated video about DC motors. Interactive Tutorials. Electric motors turn electricity into motion by exploiting electromagnetic induction. Cumulative and differential compound DC motors can have long or short shunts; this is based on the shunting of the shunt field winding. Brushless DC motors have a permanent magnet rotor and a coil wound stator.
This design of DC motor removes the need for brushes. The benefit of a brushless DC motor is the elimination of wear and tear of brushes since very little heat is produced by the rotating magnet. The efficiency of brushless DC motors makes them more expensive. A servo DC motor has four parts: a DC motor, gearbox, control circuit, and position sensing unit.
The gearbox changes high speed input into slower practical speed. The control circuit is an error detector amplifier. The position of the shaft gives feedback to the control circuit and is in a closed loop. With a servo DC motor, if there is any mismatch between the current position of the shaft and its reference position, an error signal is sent to the error detecting amplifier.
A DC motor is based on the idea that when a current carrying conductor is placed in a magnetic field, it produces mechanical force. The direction of the force is determined by the left hand rule. Since DC motors and DC generators have the same construction, they can be used interchangeably. For large electrical applications, such as steel mills and electric trains, alternating current AC is converted into DC current since the speed and torque characteristics of a DC motor are superior to an AC motor.
In the case of industrial applications, DC motors are as widely used as three phase induction motors. The stator is the unmoving main body of the motor, and it provides support and protection for the motor.
The stator provides a rotating magnetic field that drives the armature or rotor. It is the static part of the motor that houses the field windings and receives the electrical supply through its terminals.
The windings and the commutator rotate the shaft, which is at the center of the motor and made of a hardened metal, usually steel, to withstand the loads of the application. The commutator bars are attached to the plate that is affixed to the shaft by plastic molding. The torque that is produced by the winding is transferred to the shaft supported by the stator.
The shaft protrudes through the stator and connects the motor to the application. A DC motor has two terminals: positive and negative. When the positive wire is connected to the positive terminal and the negative wire connected to the negative terminal, the motor rotates clockwise. When they are reversed, the motor rotates counter clockwise. The terminals provide the power supply for the motor and are connected to the brushes and brush arms inside the back cover.
The magnets used in DC motors are referred to as permanent magnets; this means their magnetic field is always active. Opposite ends of magnets attract while similar ends repel.
The magnetic field of a magnet runs from the south pole to the north pole. Two magnets create a very strong field; this is why two magnets are included in a DC motor around the rotor such that the strong magnetic field passes through the rotor. The rotor or armature is made of multiple disks that are insulated from each other by laminated sheets. The multiple disks prevent the creation of a large eddy current. Eddy currents are the reason the plates are insulated.
Eddy currents are still present but are much smaller and do not interfere with the operation of the motor; they are a necessary part of the motor's operation. For greater motor efficiency, the disks of the rotor are made as small as possible. The rotor is the dynamic part of the motor that is used to create the mechanical revolutions. The coil windings are wrapped around the rotor.
The coiling of the wire creates a strong and powerful magnetic field. Every type of wire creates a weak magnetic field when electricity passes through it.
Due to coiling of the wire, each turned section has the same weak magnetic field. When combined with all the different coiled wire, a strong magnetic field is created. As more coils are added to the rotor, its rotation becomes smoother. All DC motors have a minimum of three coils to ensure smooth rotation since two coils tend to jam and stop the motor. The overload capability is strong and the electromagnetic interference is small. A disadvantage of the DC motor is the structure.
There is a sliding contact between the commutator and the brush. This causes sparks and mechanical wear. Direct Current motors have relatively short life expectancy because of this and the motor has high maintenance cost. It also raises reliability concerns. Skip to content You Are Here:. DC motor, how it works? How a DC motor actually works. DC motor applications. Four types of Direct Current DC motors. Advantages and disadvantages of a DC motor. Direct Drive Motors by Magnetic Innovations.
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