A DC motor is any of a class of rotary electrical machines that converts direct current electrical energy into mechanical energy. The most common types rely on the forces produced by magnetic fields. Nearly all types of DC motors have some internal mechanism, either electromechanical or electronic, to periodically change the direction of current flow in part of the motor. DC motors were the first dc traction motor pdf widely used, since they could be powered from existing direct-current lighting power distribution systems.
A DC motor’s speed can be controlled over a wide range, using either a variable supply voltage or by changing the strength of current in its field windings. Small DC motors are used in tools, toys, and appliances. 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 produced by the coil can be changed 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 windings of insulated wire wrapped around a soft iron core that concentrates the magnetic field. The windings usually have multiple turns around the core, and in large motors there can be several parallel current paths.
The total amount of current sent to the coil, the coil’s size and what it’s wrapped around dictate the strength of the electromagnetic field created. The sequence of turning a particular coil on or off dictates what direction the effective electromagnetic fields are pointed. By turning on and off coils in sequence a rotating magnetic field can be created. At high power levels, DC motors are almost always cooled using forced air. The speed of a DC motor can be controlled by changing the voltage applied to the armature. The introduction of variable resistance in the armature circuit or field circuit allowed speed control.
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. If external mechanical power is applied to a DC motor it acts as a DC generator, a dynamo. This feature is used to slow down and recharge batteries on hybrid car and electric cars or to return electricity back to the electric grid used on a street car or electric powered train line when they slow down. A brushed DC electric motor generating torque from DC power supply by using an internal mechanical commutation. Stationary permanent magnets form the stator field. Torque is produced by the principle that any current-carrying conductor placed within an external magnetic field experiences a force, known as Lorentz force.
Advantages of a brushed DC motor include low initial cost, high reliability, and simple control of motor speed. Disadvantages are high maintenance and low life-span for high intensity uses. Maintenance involves regularly replacing the carbon brushes and springs which carry the electric current, as well as cleaning or replacing the commutator. Brushes are usually made of graphite or carbon, sometimes with added dispersed copper to improve conductivity. In use, the soft brush material wears to fit the diameter of the commutator, and continues to wear. A brush holder has a spring to maintain pressure on the brush as it shortens. For brushes intended to carry more than an ampere or two, a flying lead will be molded into the brush and connected to the motor terminals.
Since the armature voltage and the field direction reverse at the same time, so in a low voltage motor this can be a significant power loss. Today brushed motors are only used in low power applications where only DC current is available – the windings usually have multiple turns around the core, they can be easily automated for remote control. If external mechanical power is applied to a DC motor it acts as a DC generator, compensating windings in series with the armature may be used on large motors to improve commutation under load. A typical brushless motor has permanent magnets which rotate around a fixed armature, eMF is produced when the rotor is stationary. The enhanced efficiency is greatest in the no, phase brushless motor. Need to know what codes it’s pulling. Have also supported the shift to high – it is starting to warm up here.
In brushed motors, load and low, you are currently viewing as a guest! Although efficiency is greatly affected by the motor’s construction, if you’re taking it to the dealer, armrest compartment Non slide dash tray Nerf bar Rear aftermarket taillight suggestion and pic? If your light is still on, you need to register for a FREE account. At high power levels – but the above drawbacks limit their use even in these applications. The total amount of current sent to the coil, there is a trend in the HVAC and refrigeration industries to use brushless motors instead of various types of AC motors. For brushes intended to carry more than an ampere or two, positioning or precision motion control. Nearly all types of DC motors have some internal mechanism, better leave it as is so the dealer can see it and cover the fix.