What Is A DC Motor?
A DC motor is a motor that transforms electrical energy into mechanical energy by drawing in direct current. DC motors induce a rotation movement in the machine by electromagnetism. DC motors have inductors (electromagnet) within them that create a magnetic field that aids the rotation of the motor.
The electromagnet is a piece of iron with wire coil windings around it. This coil has current running through its terminals. This alignment has two stationary magnets on both the sides of the electromagnet. The opposing and attractive forces of these magnets create a torque.
In a simple DC motor, there is a fixed set of magnets in the stator. It has an armature with one or more windings of insulated wire wrapped around a soft iron core. This iron core concentrates the magnetic field produced. The ends of the wire winding are connected to a commutator that powers up and energizes each armature coil. The strength of the electromagnetic field thus created, depends upon the amount of current passing through the coil, its size and the material around which it is wrapped.
A rotating magnetic field can be created by merely turning these coils on and off in a sequence. Now, when this rotating magnetic field interacts with the magnetic fields of the magnets (permanent or electromagnet), it exerts a force on the armature which sets it in a rotation motion. By altering the direction and magnitude of the of the current flowing through the coils, you can change the direction and magnitude of the magnetic field produced by it.
Types Of DC Motor
DC motors can be classified into four basic categories:
- Permanent Magnet DC Motors
In a permanent magnet DC motor, a permanent magnet is used to produce the magnetic field flux. It does not have a field winding on the stator frame and relies on permanent magnets to create the magnetic field against the opposing force of the rotor field to produce torque. It generates a good starting torque and provides a decent speed. These motors are usually found in applications running on low horsepower.
- Series DC Motors
In a series, DC motor, the field windings, and the armature are connected in series to a common D.C. power source. This motor has a very high starting torque and is used for starting high inertia loads (e.g. trains, elevators).
- Shunt DC Motors
In a shunt, DC motor, the field windings, and the armature are connected parallel (shunt) to each other with a common D.C. power source. These motors provide excellent speed regulation because the parallel field can be excited separately from the armature windings. Shunt DC motors are mostly used for industrial, adjustable speed applications (e.g. machine tools, winding/unwinding machines)
- Compound DC Motors
In a compound DC Motor, the field windings, and the armature are connected in a combination of both shunt and series, thus, imparting to it the certain features of both a shunt and series DC motor. This motor can be connected in two different arrangements: cumulatively or differentially. While cumulative compound motors connect the series field to aid the shunt field (higher torque, less speed regulation), the differential compound DC motors provide good speed regulation while operating at constant speed.
How Do DC Ceiling Fans Work?
A DC ceiling fan works pretty much on the same principle as the DC motor. A DC motor uses an internal arrangement of magnets with opposing polarity. As current passes through the coil around this arrangement, a strong magnetic field is produced. This magnetic field then creates a torque that causes the motor to rotate. Ceiling fans specifically use the brushless DC motor, that is, the synchronous DC motor.
DC motors require less electrical energy and help to minimize power consumption up to 70%.
Why Choose A Dc Ceiling Fan?
It is the general verdict that DC ceiling fans are much better than their AC counterparts. Here are some reasons to support this claim:
- Most DC ceiling fan models consume less power, in some cases, up to 70% less than a standard AC fan.
- They have a reputation for being extremely quiet.
- DC ceiling fans often come with a remote control having more speed options, a reverse button, and so on.
- A DC motor is usually quite compact and light owing to which DC ceiling fans have a slimmer motor design.
- DC ceiling fans do not get overheated, and hence, they are much more durable than any other conventional ceiling fan.
Types Of DC Ceiling Fans:
Generally, there are two types of DC ceiling fans: brushed DC fans and brushless DC fans.
Brushed DC Fan: A brushed DC fan used DC motor with brushes. A simple brush DC motor consists of a rotor, a commutator, an axle, brushes, and a permanent magnet. Brushed DC fans are not very popular because one needs to change the brushes from time to time as they tend to wear out due to constant mechanical contact with the commutator.
Brushless DC Fan: As the name suggests, brushless DC fans use brushless DC motors (BLDC motor). In these motors, usually, four magnets are mounted on the sides of the rotor in a cross pattern. It does not require any commutator or brushes to run. BLDC fans are further classified into two categories:
- BLDC fan with Sensor Motor: These fans come with a sensor known as half effect sensor to detect the position of the magnet.
- BLDC fan with Sensor-less Motor: Instead of a sensor, back EMF is used to detect the position of the magnet. The sensorless design adds to the efficiency and longevity of the motor.