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 things in motion and maintain them moving without moving a muscle? While steam engines create mechanical energy using warm 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, that includes a similar structure. Generators transform mechanic movement into electric power. The physical basis of both processes may be the electromagnetic induction. In a generator, current is definitely induced and electricity is created when a conductor is within 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 includes a stator and a rotor. The term “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 works as a coil and generates a rotating magnetic field when current is usually flowing through the wires. This magnetic field developed 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 engine serves to apply the created rotary motion in order to drive a equipment unit (as torque converter and speed variator) or even to directly drive an application as line motor.
What forms of electric motors can be found?
All inventions started with the DC electric motor. Nowadays however, AC motors of varied 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.
As with most electric motors, DC motors consist of an immobile part, the stator, and a moving element, the rotor. The stator consists either of a power magnet used 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 can be located, also known as armature, that is wrapped by a coil. If the coil is connected to a source of direct current (a electric battery, accumulator, or DC voltage supply device), it creates a magnetic field and the ferromagnetic primary of the rotor becomes an electromagnet. The rotor is usually movable mounted via bearings and may 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 southern pole of the stator, and the other method round.
In order to arranged the rotor in a continuous rotary movement, the magnetic alignment should be reversed again and again. This is attained by changing the current path in the coil. The engine has a so-known as commutator for this function. Both 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 electric vehicles.
Asynchronous AC motors
Instead of direct current, an AC motor requires three-phase alternating electric current. In asynchronous motors, the rotor is usually a so-known as 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 engine 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 since the circumferential rate of the electromagnetically induced rotor never reaches the rotational velocity of the magnetic field (rotating field). For this reason slip, the efficiency 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 swiftness 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 look of synchronous motors can be a lot more complex and time-consuming.
Additional information about synchronous motors and our portfolio
As well as the rotating devices that are mainly used on the market, drives for motions 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.
Ac Induction Motor That’s 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 (monitor 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 electric motor and rotates in a circle there, is pulled over 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 information regarding linear motors and our drive solutions