DC Motors

Motors are used in many appliances in the present day. Motors are used in home environments to industrial environments where different speeds and powers are required. The operation of a motor is made different to match the task that it is used for. Mainly, moors are of two types Alternating Current motors and Direct Current motors. The difference in these motors is because of the current they require to operate; alternate and direct current. AC motors are categorized into single phase or three phase motors. DC motors come in a variety of types.

The basic DC motor has six parts: field magnets, brushes stator, rotor, commutator and axle. Some brush-less motors do not contain brushes. Motors use electromagnetism to produce motion where a conductor carrying a current generates a magnetic field. When this magnetic field is placed in an external magnetic field, a force is produced which depends on the current supplied to the conductor. The interaction between a conductor carrying an electric current and the external magnetic field causes a rotational motion in a DC motor.

There are three types of DC motors which run on different values of current:

• Low power DC motors- These motors are not heavy duty motors. They provide quick acceleration to the small speed that the motors work at. Although they are not powerful these motors are precise. Low voltage DC motors are used in hard drives, processor cooler fans, CD & and DVD players.

• Medium power DC motors- These motors are powered by a rectifier attached to them which converts AC current to DC current and is directly connected to the main power. Medium power DC motors are used in instances where power and speed is not required, just reliability is required.

• High power DC motors- These motors are the most commonly used motors which are suitable for most requirements. They provide great power and torque. Examples where these motors are used are in elevators and hybrid cars.

There are four types of DC motors according to their structure:

• Brushed motors- A brushed DC motor produces motion from the DC current supplied to it interacting with stationary and moving magnets. The force hence produced is called Lorentz force. The cost of a brushed DC motor is less than a brush-less motor, they are reliable and the speed can be controlled. The downside is that they require a lot of maintenance.

• Synchronous DC motors- These motors require an initial external torque to get the motor running. If directly run by DC current, they will not run and get stuck.

• Brush-less DC motors- In these motors, there are permanent magnets on the rotor and electromagnets on the walls of the motor body. The DC current supplied to the motor is converted to AC current by a motor controller. Since the rotor is a permanent magnet and the housing magnets are electromagnetic, there is no need for brushes or transferring current to the rotor. Highly efficient and no maintenance required, have a long lifespan. The only problem is that a brush-less motor is expensive.

• Non-commutated motors- Other motors are the kind of motors which need no commutation. They are of two types, homo polar and ball bearing motors.