In order to solve the problems of monitoring modern precision systems, a valve motor is increasingly being used. This is characterized by the great advantage of such devices, as well as the active formation of the computing capabilities of microelectronics. As you know, they can provide a high density of long torque and energy efficiency compared to other types of engines.
Valve motor circuit
The engine consists of the following parts:
1. The back of the case.
2. The stator.
3. Bearing.
4. Magnetic disk (rotor).
5. Bearing.
6. Stator with winding.
7. The front of the case.
The valve motor has a relationship between the multiphase winding of the stator and rotor. They have permanent magnets and a built-in position sensor. Switching the device is implemented using a valve converter, as a result of which he received this name.
The valve motor circuit consists of a back cover and a sensor printed circuit board , a bearing sleeve, a shaft and the bearing itself, rotor magnets, an insulating ring, a coil, a coil spring, an intermediate sleeve, a Hall sensor, insulation, housing and wires.
In the case of connecting the windings with a "star", the device has large constant moments, so this assembly is used to control the axes. In the case of fastening the windings with a "triangle", they can be used to work with high speeds. Most often, the number of pole pairs is calculated by the number of rotor magnets that help determine the ratio of electrical and mechanical revolutions.
The stator can be made with an iron or iron core. Using such constructions with the first option, it is possible to ensure the absence of attraction of the rotor magnets, but even at that instant the engine efficiency is reduced by 20% due to a decrease in the constant torque value.
The diagram shows that in the stator current is generated in the windings, and in the rotor it is created using high-energy permanent magnets.
Legend:
- VT1-VT7 - transistor communicators;
- A, B, C - phase windings;
- M - engine torque;
- DR - rotor position sensor;
- U - motor voltage regulator;
- S (south), N (north) - direction of the magnet;
- UZ - frequency converter;
- BR - speed sensor;
- VD - zener diode;
- L - inductor.
The engine diagram shows that one of the main advantages of the rotor, in which the permanent magnets are installed, is to reduce its diameter and, as a result, reduce the moment of inertia. Such devices can be built into the device itself or located on its surface. Lowering this indicator very often leads to small values of the balance of the moment of inertia of the engine itself and the load brought to its shaft, which complicates the operation of the drive. For this reason, manufacturers can offer standard and 2-4 times increased moment of inertia.
Work principles
Today, a valve motor is becoming very popular, the principle of which is based on the fact that the controller of the device starts switching the stator windings. Due to this, the magnetic field vector remains always shifted by an angle approaching 900 (-900) relative to the rotor. The controller is designed to control the current that moves through the motor windings, including the magnitude of the stator magnetic field. Therefore, it is possible to adjust the moment that affects the device. The measure of the angle between the vectors can determine the direction of rotation that acts on it.
It must be borne in mind that we are talking about electrical degrees (they are much less than geometric degrees). For example, we give the calculation of a valve motor with a rotor, which in itself has 3 pairs of poles. Then its optimum angle will be 900/3 = 300. These pairs provide for 6 phases of switching windings, then it turns out that the stator vector can move in jumps of 600. It can be seen from this that the real angle between the vectors will necessarily vary from 600 to 1200, starting with the rotation of the rotor.
A valve motor, the principle of which is based on the rotation of the switching phases, due to which the excitation flux is supported by the relatively constant movement of the armature, after their interaction begins to form a torque. He seeks to rotate the rotor in such a way that all the flows of excitation and anchors coincide together. But during its turn, the sensor starts switching the windings, and the flow moves to the next step. At this moment, the resulting vector will move, but will remain completely stationary compared to the flow of the rotor, which will ultimately create the shaft torque.
Benefits
Applying a valve motor in operation, one can note its advantages:
- the possibility of using a wide range to modify the speed;
- high dynamics and speed;
- maximum positioning accuracy;
- low maintenance costs;
- the device can be attributed to explosion-proof objects;
- has the ability to carry large overloads at the time of rotation;
- high efficiency, which is more than 90%;
- there are sliding electronic contacts that significantly increase the working life and service life;
- during prolonged operation there is no overheating of the electric motor.
disadvantages
Despite the huge number of advantages, the valve motor also has disadvantages in operation:
- a rather complicated motor control;
- the relatively high price of the device due to the use of a rotor in its design, which has expensive permanent magnets.
Induction motor
An inductive induction motor is a device in which a switching magnetic resistance is provided. In it, energy conversion occurs due to changes in the inductance of the windings, which are located on the pronounced teeth of the stator when moving the gear magnetic rotor. The device receives power from an electric converter, which alternately switches the motor windings in strictness with respect to the rotor movement.
The induction induction motor is a complex complex system in which components of various physical nature work together. For the successful design of such devices, in-depth knowledge is needed in the field of designing machines and mechanics, as well as electronics, electromechanics and microprocessor technology.
The modern device acts as an electric motor, acting in conjunction with an electronic converter, which is manufactured using integrated technology using a microprocessor. It allows for high-quality engine management with the best energy processing performance.
Engine properties
Such devices have high dynamics, high overload capacity and precise positioning. Due to the fact that they do not have moving parts, their use is possible in explosive aggressive environments. Such motors are also called brushless motors, their main advantage over collector motors is the speed, which depends on the supply voltage of the load moment. Another important property is the absence of abrasion and rubbing elements that switch contacts, which increases the resource for using the device.
DC Motors
All DC motors can be called brushless. They work from a network with a direct current. A brush assembly is provided for electrically combining the rotor and stator circuits. Such a part is the most vulnerable and quite difficult to maintain and repair.
The DC brushless motor operates on the same principle as all synchronous devices of this type. It is a closed system, including a power semiconductor converter, a rotor position sensor and a coordinator.
AC Motors
Such devices get their power from AC networks . The speed of rotation of the rotor and the movement of the first harmonic of the magnetic force of the stator completely coincide. This subtype of engines can be used at high power. This group includes stepper and reactive valve apparatuses. A distinctive feature of stepper devices is a discrete angular displacement of the rotor during its operation. The power of the windings is formed using semiconductor components. The valve motor is controlled by sequential displacement of the rotor, which creates a switching of its power from one winding to another. This device can be divided into single, three and multiphase, the first of which may contain a starting winding or phase-shifting circuit, as well as start manually.
The principle of operation of the synchronous motor
The synchronous valve motor operates on the basis of the interaction of the magnetic fields of the rotor and stator. Schematically, the magnetic field during rotation can be represented by the pluses of the same magnets, which move with the speed of the stator magnetic field. The rotor field can also be represented as a permanent magnet, which rotates in synchronism with the stator field. In the absence of external torque, which is applied to the apparatus shaft, the axes completely coincide. The acting forces of attraction pass along the entire axis of the poles and can cancel each other out. The angle between them is equal to zero.
If the braking moment acts on the machine shaft, the rotor moves laterally. Due to this , the attractive forces are divided into components that are directed along the axis of positive indicators and perpendicular to the axis of the poles. If an external moment is applied that creates acceleration, that is, it begins to act in the direction of rotation of the shaft, the picture of the interaction of the fields will completely reverse. The direction of the angular displacement begins to be transformed to the opposite, and in this regard, the direction of the tangential forces and the influence of the electromagnetic moment change. In this situation, the engine becomes braking, and the device operates as a generator, which converts the mechanical energy supplied to the shaft into electrical energy. Then it is redirected to the network supplying the stator.
When there is no external, explicit pole moment will begin to take a position in which the axis of the poles of the stator magnetic field will coincide with the longitudinal. This placement will correspond to the minimum flow resistance in the stator.
If the rotor moment is applied to the machine shaft, the rotor will deflect, and the stator magnetic field will be deformed, as the flow tends to close at the lowest resistance. To determine it, force lines are needed, the direction of which at each point will correspond to the movement of the force, therefore, a change in the field will lead to the appearance of a tangential interaction.
Having considered all these processes in synchronous motors, we can identify the demonstrative principle of reversibility of various machines, that is, the ability of any electrical apparatus to change the direction of converted energy to the opposite.
Permanent Magnet Brushless Motors
A permanent magnet permanent magnet motor is used to solve serious defense and industrial problems, since such a device has a large supply of power and efficiency.
These devices are most often used in industries where relatively low power consumption and small dimensions are needed. They can have a variety of dimensions, without technological restrictions. At the same time, large devices are not completely new; they are most often produced by companies that seek to overcome the economic difficulties that limit the range of these devices. They have their own advantages, among which high efficiency due to losses in the rotor and high power density can be noted. To control brushless motors, a variable frequency drive is needed.
Analysis of costs and results shows that devices with permanent magnets are much preferable in comparison with other alternative technologies. Most often they are used for industries with a rather heavy operating schedule of marine engines, in the military and defense industries and other units, the number of which is constantly growing.
Jet engine
The fan-jet engine operates using two-phase windings that are installed around diametrically opposite stator poles. The power supply advances towards the rotor in accordance with the poles. Thus, his opposition is completely minimized.
A self-made valve motor provides highly efficient drive speed with optimized magnetism for reverse operation. Information about the location of the rotor is used to control the phases of the voltage supply, as this is optimal for achieving continuous and smooth torque and high efficiency.
The signals generated by the jet engine are superimposed on the angular unsaturated phase of the inductance. The minimum pole resistance is fully consistent with the maximum inductance of the device.
A positive moment can only be obtained at angles when the indicators are positive. At low speeds, the phase current must be limited in order to protect the electronics from high volt-seconds.
The conversion mechanism can be illustrated by a line of reactive energy. The power sphere is characterized by nutrition, which is converted into mechanical energy. In the event of a sudden shutdown, excess or residual force returns to the stator. Minimum indicators of the influence of the magnetic field on the performance of the device are its main difference from similar devices.