The benefits of using DC motors is their simple speed and control of torque. Since a lot of simple household appliances make use of these motors, DC motor speed control cannot be ignored. Having a simple mechanism makes it possible for these motors to be used in industries too. Their working is based on the principle of polarity of magnets i.e., unlike poles attract and like poles repel. Making use of this allows us to convert electrical energy into mechanical energy.
There are a few different types of DC motors. In the series wound type, the DC motor speed control is poor. But it can be varied by controlling the supply voltage. In the case of a shunt wound motor, the speed is controlled by a process called field weakening. Using a rheostat, the field current and thereby the flux in the air gap are controlled. This way, there is no variation in the voltage. With a fixed voltage, this shunt wound motor is able to run at a constant speed and finds uses in windscreen wipers, which need fixed speeds.
Considering the fact that DC motor speed control is so necessary for using it with convenience, it is not too difficult a process. Get the DC motor for your needs from good companies that sell them like Teco Electric Co. Ltd. so that you are sure of the quality.