Electric motor

Electric motor
Electric motor, some of a class of devices that convert electrical energy to mechanical energy, usually by using electromagnetic phenomena.

What is an electric motor?
How can you bring stuff in motion and keep them moving without moving a muscles? While steam engines create mechanical energy using hot steam or, more precisely, steam pressure, electric motors use electric energy as their resource. For this reason, electric motors are also called electromechanical transducers.

The counter piece to the electric engine is the generator, which has a similar structure. Generators transform mechanic movement into energy. The physical basis of both processes is the electromagnetic induction. In a generator, current is definitely induced and electricity is created when a conductor is at a shifting magnetic field. Meanwhile, within an electric motor a current-transporting conductor induces magnetic areas. Their alternating forces of appeal and repulsion make the basis for generating motion.
How does an electric motor work?
Motor housing with stator
Motor housing with stator
In general, the heart of an electric motor consists of a stator and a rotor. The word “stator” is derived from the Latin verb “stare” = “to stand still”. The stator is the immobile component of an electric motor. It is firmly attached to the equally immobile housing. The rotor on the contrary is mounted to the engine shaft and can move (rotate).
In the event of AC motors, the stator includes the so-called laminated core, which is wrapped in copper wires. The winding functions as a coil and generates a rotating magnetic field when current is usually flowing through the wires. This magnetic field produced by the stator induces a current in the rotor. This current then generates an electromagnetic field around the rotor. As a result, the rotor (and the attached engine shaft) rotate to check out the rotating magnetic field of the stator.

The electric motor serves to apply the created rotary movement to be able to drive a equipment unit (as torque converter and speed variator) or even to directly drive a credit card applicatoin as line motor.
What types of electric motors can be found?
All inventions began with the DC electric motor. Nowadays however, AC motors of various designs are the most commonly used electric motors in the industry. They all possess a common result: The rotary motion of the electric motor axis. The function of AC motors is founded on the electromagnetic working basic principle of the DC electric motor.

DC motors
As with most electrical motors, DC motors consist of an immobile part, the stator, and a moving element, the rotor. The stator consists either of a power magnet utilized to induce the magnetic field, or of long term magnets that continuously generate a magnetic field. Within the stator is where in fact the rotor is definitely located, also known as armature, that is wrapped by a coil. If the coil is connected to a way to obtain direct current (a electric battery, accumulator, or DC voltage supply unit), it generates a magnetic field and the ferromagnetic core of the rotor becomes an electromagnet. The rotor is usually movable mounted via bearings and can rotate to ensure that it aligns with the attracting, i.e. opposing poles of the magnetic field – with the north pole of the armature opposite of the south pole of the stator, and the other way round.

In order to arranged the rotor in a continuous rotary movement, the magnetic alignment must be reversed over and over. This is attained by changing the current path in the coil. The engine has a so-known as commutator for this function. The two supply contacts are linked to the commutator and it assumes the duty of polarity reversal. The changing attraction and repulsion forces make sure that the armature/rotor proceeds to rotate.

DC motors are mainly used in applications with low power ratings. These include smaller equipment, hoists, elevators or electrical vehicles.

Asynchronous AC motors
Instead of direct current, an AC motor requires three-phase alternating electric current. In asynchronous motors, the rotor is a so-called squirrel cage rotor. Turning results from electromagnetic induction of this rotor. The stator includes windings (coils) offset by 120° (triangular) for every stage of the three-phase current. When linked to the three-stage current, these coils each build up a magnetic field which rotates in the rhythm of the temporally offset range frequency. The electromagnetically induced rotor is carried along by these magnetic fields and rotates. A commutator as with the DC motor is not required in this way.

Asynchronous motors are also called induction motors, as they function only via the electromagnetically induced voltage. They run asynchronously because the circumferential rate of the electromagnetically induced rotor by no means reaches the Ac Induction Motor rotational velocity of the magnetic field (rotating field). Because of this slip, the performance of asynchronous AC motors is lower than that of DC motors.

More on the structure of AC motors / asynchronous motors and on what we offer

AC synchronous motors
In synchronous motors, the rotor has permanent magnets rather than windings or conductor rods. In this manner the electromagnetic induction of the rotor could be omitted and the rotor rotates synchronously without slide at the same circumferential acceleration as that of the stator magnetic field. Effectiveness, power density and the feasible speeds are thus significantly higher with synchronous motors than with asynchronous motors. However, the design of synchronous motors is also a lot more complex and time-consuming.

Additional information about synchronous motors and our portfolio

Linear motors
As well as the rotating devices that are mainly used in the industry, drives for movements on straight or curved tracks are also required. Such movement profiles occur mainly in machine tools as well as positioning and managing systems.

Rotating electric motors may also convert their rotary motion into a linear motion using a gear unit, we.e. they are able to cause it indirectly. Often, however, they don’t have the necessary dynamics to realize particularly challenging and fast “translational” movements or positioning.

This is where linear motors enter into play that generate the translational motion directly (direct drives). Their function could be produced from the rotating electric motors. To get this done, imagine a rotating electric motor “exposed”: The previously round stator becomes a flat travel distance (track or rail) which is certainly covered. The magnetic field then forms along this path. In the linear engine, the rotor, which corresponds to the rotor in the three-phase engine and rotates in a circle there, is stopped the travel distance in a straight line or in curves by the longitudinally moving magnetic field of the stator as a so-known as carriage or translator.

More details about linear motors and our drive solutions


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