Electric Motor: how is it made?
Electric motor: how is it made?
The electric motor is an electric machine: the input power is electric, the output power is mechanical. Electric motors are of fundamental importance in plants and machinery where they are installed to make a movement. 75% of the electricity consumed in the industrial sector is used to power electric motors.
The electric motor is used for many applications in industry, agricultural machinery, transport (railway, subway, tram), domestic equipment etc. It is therefore of primary importance, also from the point of view of energy saving, to know the efficiency of an electric motor.
Inverters, electric motors
An inverter, also called Variable Speed ??Drive (VSD, speed variator) is an electronic device powered directly from the electrical network, designed to vary the frequency and amplitude of the power supply voltage of an electric motor. Thanks to a sophisticated control, the inverter is also able to vary the rotation speed of the motor itself. The inverter is a device that radically changed automation in the industry, introducing the ability to adjust the speed of induction motors with very low costs, both for installation and operation.
Electric motor: stator and rotor
The electric motor is made up of two parts: a fixed part, called the stator, and a moving part called the rotor. In these two components, two magnetic fluxes are generated, respectively the stator flux and the rotor flux. Those interacting with each other, give rise to a pair of forces that causes the rotational movement of the motor shaft which is usually integral with the Rotor.
The stator is the fixed part, and is the seat of the windings called inductors. The windings are made with enamelled copper wire and are housed in the slots specially made in the stator.
The rotor in electric motors is also called induced and is the rotating part. The type of rotor changes according to the type of electric motor (squirrel cage, permanent magnet or wound).
Synchronous or Asynchronous electric motor
There are mainly two types of electric motor: synchronous electric motor and asynchronous electric motor.
- The synchronous motor owes its name to the fact that the rotor rotation frequency is synchronized with the frequency of the rotating magnetic field and the frequency of the supply voltage.
- The asynchronous motor, on the other hand, is a type of electric motor in alternating current in which the rotor’s rotation frequency is not equal to the frequency of the supply voltage, that is, it is not "synchronous" with it; this is why it differs from synchronous motors.
The advantages and disadvantages of synchronous and asynchronous motors
- Asynchronous motor
The asynchronous electric motor is robust and reliable and is widely used in industry. Less expensive engines and reduced maintenance costs. They are self-starting motors, capable of withstanding an overload up to 2.5 times the rated power. The major drawback is their much lower efficiency compared to the synchronous motor, especially at low speeds. They have a modest reactivity in the control phase. - Synchronous motor
The synchronous motor offers the possibility of very precise speed control as the rotor exactly and constantly follows the rotating field. It has a high yield. The control of a synchronous motor is very good in applications where very fast dynamics and / or high accuracy are required. The disadvantages are related to the higher cost of the control system.
Non-standard Special Electric Motors
It is possible to choose, according to your needs, special electric motors.
The Carpanelli Company has been specializing, for over 70 years, in the design and manufacture of non-standard asynchronous electric motors: custom-made motors made according to the specific needs of each customer.
Customized, non-standard, special motors: tailor-made solutions for those who need electric motors with particular applications, Made in Italy, always reliable, with the highest quality.