In order to talk about motion control, it would perhaps be necessary to devote some time to the element that converts the electrical energy into mechanical. We are surrounded by electric motors: the small motor that spins a hard disk, the Kelvin motor that moves the elevator, the toothbrush, the pump station, in factories, in training, in hospitals. About 70% of the electrical energy is used to power motors we are surrounded!
By its construction, its application and its technology there are a lot of different engines and not all of them rotating! Despite the fact that today, when we talk about engines, almost always we think of alternating current motors, for many years, DC motors have had a very important role, because, in spite of its price, (due to their mechanical complexity and maintenance), they were certainly much easier to control than their ‘brothers’ of alternating current.
DC or AC current?
Today it seems question is somewhat out of place, since the distribution systems conventional are all alternate (more efficient for the transport of power), but in its origins there was a great rivalry between the advocates of direct current (Thomas A. Edison) and those who preferred the alternating current (Nikola Tesla).
About Edison… what can you say? one of the inventors more prolific and with greater business acumen of the Story and that I sincerely we need plenty of items. The second one, Tesla, well, we have to suppose that anything was done since the unit of measurement of the magnetic field bears his name. Nikola Tesla is, in my opinion worthy of the name of a street in everu city. Tesla, not only did research ‘mind-blowing’ for his time in the field of electromagnetism, but that was the great forerunner of the transmission systems multi-phase (three-phase, the most common), and in turn, the precursor of the alternating current motors.
Needless to say, Tesla and Edison were rivals, even the enmity is personal. Without Tesla our world would be very different, and it’s Justice to vindicate the figure of Tesla as one of the fathers of electrical engineering.
AC motors or continuous motors?
What we are interested in an engine? Typically, we are interested in two quantities: Speed and engine Torque. What do Speed and Torque depend on? The engine Torque is brute force, more amps equals more torque, therefore I just need to be able to regulate the amps for more or less torque (force).
The Speed of a motor depends on what? Therefore, in order to answer this question it should be indicated if it is a motor of continuous current or alternating current. In a DC motor, more volts, more rpm! But in a alternating current motor more volts not necessarily translate into more speed, since the speed of an ac motor depends on its construction (pairs of poles) and the frequency of stator excitation, typically 50 Hz or 60 Hz.