today to imagine human civilization and high-tech society is impossible without electricity.One of the key devices that provide electrical appliances, is the engine.This machine has found the most widespread: from the industry (fans, crushers, compressors) to domestic use (washing machines, drills, etc.).But what is the principle of operation of the motor?
Purpose Principle of operation of the electric motor and its main objectives are to transfer working bodies necessary for the fulfillment of the technological processes of mechanical energy.The engine itself generates it by the electricity consumed from the grid.As a matter of fact, the principle of operation of the motor is to convert electrical energy into mechanical energy.The amount of mechanical energy produced by them per unit time is called the capacity.
Types engines
Depending on the characteristics of the supply are two main types of output: dc and ac.The most common machines are DC motors with a consistent, independent and mixed excitation.Examples of AC motors can perform synchronous and asynchronous machines.Despite the apparent diversity, the apparatus and operation of the motor based on the destination of any interaction with the current conductor and the magnetic field, or the permanent magnet (ferromagnetic object) with the magnetic field.
frame with shock - the prototype engine
highlight in this issue is the principle of operation of the motor, it can be called the emergence of torque.Consider such a phenomenon can be for example a current frame, which consists of two conductors, and a magnet.Current is applied to the conductor through the slip rings which are fixed on the axis of the rotating frame.In accordance with the famous rule of the left hand on the frame will work forces that create torque about the axis.It is under the action of the total force will rotate counterclockwise.It is known that the torque is directly proportional to the magnetic induction (B), a current (I), the square frame (S) and is dependent on the angle between the field lines and the axis of the latter.However, under the influence of the time-varying in its direction, the frame will oscillate.What to take to form a constant direction?There are two options:
- change the direction of the electric current in the wire frame and the position relative to the poles of the magnet;
- change the direction of the field, despite the fact that the frame is rotated in a constant direction.
first option used for DC motors.And the second - is the principle of the AC motor.
change in the current direction relative to the magnet
In order to change the direction of motion of charged particles in a conductor with a current frame, a device that would specify this area depending on the location of the conductors.This design is realized through the use of sliding contacts, which are used to supply current to the frame.If you are replacing one of the two ring when the frame is rotated half a turn, the direction of current is reversed, and torque it retains.It is important to consider that one ring assembled from two halves which are insulated from each other.
machine design DC
above example - a principle of the DC motor.Actual vehicle naturally has a more complicated structure which uses tens of frames constituting the armature winding.The conductors of the winding are placed in special grooves in the cylindrical ferromagnetic core.The ends of the windings are connected to the isolated rings that form a manifold.Winding core collector and - an anchor, in rotatable bearings on the housing of the engine.The magnetic field created by the excitation poles of the permanent magnets which are arranged in the housing.The winding is connected to the mains, and can include both independent of the anchor chain or sequentially.In the first case, the motor will have a separate excitation in the second - a serial.There is also the construction of mixed-excitation when using just two winding connection type.
synchronous machine
principle of operation of the synchronous motor is the need to create a rotating magnetic field.Then you put in this field in the same direction streamlined current conductors.The principle of the synchronous motor, which is very common in the industry, is based on the above example, with the current frame.The rotating field generated by the magnets, is formed by means of the windings are connected to the mains.Usually they use three-phase winding, but the principle of operation of single-phase AC motor will not differ from the three-phase, except that the number of phases themselves, that is immaterial when considering the design features.The windings are placed in the stator slots with some shift circumferentially.This is done to create a rotating magnetic field formed by the air gap.
Synchronicity
very important point is the synchronized operation of the electric motor of the above construction.The interaction of the magnetic field with the current in the rotor winding is formed the process of rotation, which is synchronous with respect to the rotating magnetic field formed on the stator.The synchronism will be maintained up to the maximum torque, which is caused by resistance.When the load increases the machine can exit synchronism.
asynchronous motor operating principle of an asynchronous motor is the presence of a rotating magnetic field and closed frames (contours) on the rotor - the rotating parts.A magnetic field is formed in the same manner as that of the synchronous motor - using slots located in the stator windings are connected to an AC voltage.The rotor winding consists of a dozen loops-frames and are usually two types of performance: phase and short-circuited.The principle of operation of the AC motor in both cases is the same, changing only the design concept.In the case of a short-circuited rotor (also known as "squirrel cage") is filled with molten aluminum winding in the slots.When manufacturing the phase winding ends of each phase outputted to the outside via the sliding-contact rings as it will include a series resistor in the circuit which are necessary for controlling the engine speed.
Pulling machine
principle of operation of the traction motor is similar to the DC motor.From the mains current is supplied to step-up transformer.Next, a three-phase alternating current is passed to the special traction substations.There is a rectifier.It converts AC to DC.Under the scheme, he held one of its polarity to the contact wire, the second - directly to the rails.It must be remembered that many of the traction mechanisms operate at a frequency different from the established commercial (50 Hz).Therefore, using the motor Frequentists, the principle of which is to convert the frequency and controlling this characteristic.
for raising the pantograph voltage is supplied to the chamber, where the starting resistors and contactors.With controllers rheostats connected to traction motors, which are arranged on axles bogies.From them, a current flows through the tires on the rails and then returned to the traction substation, thus closing the electric circuit.
