Characteristics of induction motors

The electric induction motor has almost constant speed. Small power induction motors are most often single phase with shorted rotor and need special devices since they do not have their own starting. The three-phase induction motors are of higher power and have their own starting. Since they need a large current of the network, at the moment of starting, special devices are used to decrease it. In series or universal single-phase motors, the rotor winding is brought to https://www.mrosupply.com/motors/dc-motors/2525284_10801400_leeson/ the brushes by interference from a switch, which is a collector made up of blades insulated from one another and connected to the stator.

This type of electric motor works with both direct and alternating current and has variable speed. In the motor to the repulsion the winding of the rotor is taken to the brushes that are connected in short circuit. It has variable speed, being usually used as motor repulsion induction. At start it functions as a repulsion motor that has its own start and then, through a centrifugal device, the slides of the collector are shorted, starting to function as a single-phase induction motor.

Speed ​​Regulation

A problem encountered in AC motors that use frequency converters for speed control is that they eventually generate reactive power and need capacitor banks to compensate for this energy being dispensed to the power grid, and even then they will only solve around 90% of the problem. In the case of DC motors this does not happen, 011297 dodge because the speed can be regulated by the insertion of a rheostat in the field circuit, to provide correct flow.

It is preferable to use a DC motor which will not generate reactive power in relation to the total rated power of the motor. This gives the equipment extra security even if it has to use higher powers in some unforeseen circumstances.

The speed control of the alternating current motors allows the speed to be obtained from the zero axis up to twice the synchronous speed, by the known rotor system with the switch, by means of the brush offsets. In an induction motor, the speed of rotation is different from the speed of synchronism. This fact is due to the existence of a speed difference between the rotor and the rotating field of the stator. This difference is called slipping.

Induction Motor Operation

The induction motor is an engine that has its operating principle based on the creation of a rotating magnetic field. In an induction motor, the speed of rotation is different from the speed of synchronism and this fact is because there is a speed difference between the rotor and the rotating field of the stator. At this speed difference we call the slip name 471341 Small Bore Inch Seal.

Magnetic fields are measured through a magnitude called magnetic induction, which is symbolized by the letter B, whose unit is the Tesla (T). The value of B is higher in regions where the lines are more concentrated. The field winding can be single-phase or three-phase. The way this winding is established determines the number of motor poles, among other operational characteristics. Its terminals are extended to a terminal box, where the connection will be made to the mains power supply. In the region around a magnet focus some special phenomena, such as the attraction of iron fragments or the deviation of the needle from a compass. We say that in this region there is a magnetic field, which can be represented by induction lines.

FUNCTION AND COMPOSITION OF THE DEPARTURE DEVICE

Many industrial processes require variable speed load drive devices, such as pumps for varying liquid flow; fans for variation of air flow; transport systems to vary the transport speed; lathes for variation of cutting speed; winding machines to compensate for the variation of the coil diameter.

For a long time, variable speed industrial applications have been dictated by process requirements and limited by technology because of cost, efficiency and maintenance requirements and components employed. In the past, the speed variation was made by a fixed speed induction motor and was the first electric energy conversion device for mechanical energy, energy conversion device through mechanical, hydraulic or electromagnetic components (according to the energy conversion device . hose reels 112-3-100

A motor starting device joins all the components necessary to control and protect an electric motor and the selection of the components to constitute a device conditions the performance of the installation. The main components required are: protection level, fixed or variable speed operation, sectioning, protection against short circuits, protection against overload and switching.

Frequency inverters

Frequency inverters control the speed of three-phase alternating current electric motors as well as control other parameters essential to the electric motor, one of which is torque control. This versatile and dynamic equipment is widely used in many different areas and equipment such as elevators, machine tools, pumps, mechanical traction. Frequency inverters are electronic devices that convert the voltage from the alternating sinusoidal network into direct voltage and finally convert the latter into a voltage of variable amplitude and frequency.

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The speed of rotation of an induction motor depends on the frequency of the mains, as the higher the frequency, the greater the rotation and vice versa. Thus, when an induction motor is fed by a frequency inverter, it is possible to naturally control the speed of the motor shaft by means of the frequency variation imposed by the inverter. The frequency of operation of an inverter is usually between 0.5 and 400Hz, which will depend on the model and the brand. The frequency inverters have an input connected to the common power supply network, which may be single-phase or three-phase, and an output which is applied to the device to be fed, in this case a three-phase induction motor.

Static windings

Stator windings are a preponderant aspect in all types of electric motors, as they are responsible for the creation of the stator magnetic field. When we speak of three-phase motors, the stator magnetic field is acquired by the passage of current in the stator windings. These three-phase windings are formed by three circuits independent of each other, but identical and fed each one by one of the three phases. Each phase has a resolved number of coils that are housed in the stator slots and are interconnected with each other. These coils are out of phase with each other of 120 ° electrical or electric radians.

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Each coil, when fed, operates solitarily and acts as a primary coil of a transformer, producing an alternating magnetic field, but with a fixed direction. In turn, the junction of all partial magnetic fluxes gives rise to a rotating magnetic flux of constant intensity, having as many pairs of poles as groups of three coils have the stator, which depends directly on the number of pairs of poles of the stator. For the fastening of the windings in the stator, grooves are usually used, and these are divided into three large groups: Open Slots, Semi-Open Slots and Closed Slots.

Servo-motor

Large electric machines such as single-phase induction motors, synchronous motors, three-phase asynchronous motors and DC motors are used when we need continuous energy conversion. However, there are some special applications where you do not have to use a continuous power conversion process. The servomotor is different in design, construction and operation mode. The servomotor, often called the motor for control, is an electric motor specially designed and built for use in feedback control systems, playing the role of actuator element.

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The rated power of these motors can range from fractions to hundreds of watts. These motors have a high dynamic response requiring low inertia of the rotor. Another property of these engines is that they have smaller diameter and longer length. Servomotors normally operate at low speed with high torque and can operate at high speed since the speed range of the servomotors ranges from 2,000 to 6,000 revolutions per minute. Examples of applications where servo motors are used include: packers, mats with programmed stops, cutting and welding machines, graphic machines, computers, process controllers, etc.

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