Energy, Magnetism, Motors, Power systems

Types of DC motors

It was already published a post about how DC motors work, but these motors are divided by type of winding in the stator. This post will explain the various existing types.

Permanent magnet motors

In the post about DC motors, I already written how permanent magnet motors work, click in the button below to see.

DC motors DC motorsClick here

Permanent magnet motors have a good initial torque and don’t need energy to the stator. However, the stator’s magnetic field can be demagnetized for excess of current in the rotor. Serve to low power applications. This is the motor’s model of equivalent circuit. The rotor is also called armature.

This is the graphic of relation between the torque and the speed to the permanent magnet motor.

Independent excitation motors

In this type of DC motor, the stator needs a DC power source separated to generate the magnetic field. This is the equivalent circuit of this type of motor.

In the independent excitation motor, the speed is almost constant and can be controlled by the voltage in the armature (rotor) or by the stator`s winding, also called field winding. Are much used in the industry with alternate current/continuous current converters.

DC shunt or parallel motor

In this type, the field winding in the stator is parallel to the armature. Both are activate by the same source of energy. This is the equivalent circuit.

The DC motor shunt have low start torque in comparison with other types, but can keep a constant speed even with load.

DC series motor

In this type of motor, the stator coil winding is in series with the armature winding. Here is the equivalent circuit.

The DC series motor has a high start torque, but the speed is slower when you put load.

Composite DC motors long and short

This motor was made to unite the advantages of shunt and series motors. Are used in situations which requires high torque and constant speed. It is more difficult to control this motor`s speed. Here we have the circuits of composite motors long and short respectively.

When the magnetic fields generated by armature and field winding are added, it is called cumulative compounding. When stay in opposite directions is diferential compounding.

This is the graphic torque x speed.


About Pedro Ney Stroski

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