All motors perform the same basic function, whether they are AC motors or DC motors – they convert electrical power into mechanical power. This is where the similarity between the two types of motors end. AC motors operate with the alternating current while DC motors operate with direct current. AC motors also come in two types. There are one-phase motors and three-phase motors. Here is the first difference between the three phase motors and DC motors. DC motors do not have different phases. DC motors are more like batteries which also operate on direct current.
How They Work
A DC motor has a fixed magnet with coils suspended between the poles of the magnetic field. When attached to the battery it creates a magnetic field that causes the coils to flip over and run the motor. An AC motor, which a three-phase induction motor is, has a ring of electromagnets that produce a rotating magnetic field. This rotating magnetic field conducts the electricity that runs the motor.
Three-phase induction motors are less efficient than DC motors are. As they transfer between phases the current droops to zero. Since the transfer between phases is so quick it does not actually leave you without power at this point, but a DC motor provides continuous power until the power source is turned off.
The three-phase inductor motor has three phases where the DC motor has only one phase and cannot be converted to a three-phase. There are one-phase induction motors.
Brushes and Commutator
DC motors have parts called brushes and commutators. Since the currents are alternating, DC motors must convert DC current to C current to work with appliances or whatever the motor is powering. To do this it uses brushes, which carry the current to the commutator which then reverses the current to make it usable. The brushes and commutator limit the speed of the motor and reduce the life expectancy of the motor. Though they can be repaired or replaced that increases the maintenance cost of the DC motor. The three-phase induction motor does not have brushes and commutators because it is an AC motor and does not have to deal with converting the current.
Stator and Rotator Action
The three-phase inductor motor has a stator that stands still and it supplies the rotating field. The rotor on this engine is what rotates. On the DC engine, the armature is what rotates and what stands still is the field winding.
To control the speed of the three=phase inductor motor you have to change the frequency at which it operates. On the DC motor to change the speed, you change the armature winding’s current.
Speed and Torque
The three-phase induction motor is used for high speed and torque that is variable. The DC engine is better used for applications that require high torque and variable speed.
Three-phase induction motors have a slow response to changes in the load while DC motors respond quickly to load changes.
Three-phase motors are mostly used in factories and in large industries. DC motors are used for domestic applications such as household appliances.