When it comes to electric motors, there is no linear relationship between power, speed and voltage. Consider the industries in which high-voltage electric motors, high-speed motors, and high-power motors are used and how they differ.
Different types of high voltage electric motors
High voltage motors are synchronous and asynchronous motors with a voltage of 3000, 6000, 6300, 6600 and 10000 V. Basically, these electric motors are used in industry: metallurgical, mining, machine tool building, chemical industries. Such electric motors are used in installations, smoke exhausters, mills, mills, screens, fans, etc.
Three-phase motors are designed to run on alternating current with a frequency of 50 (60) Hz. To provide reliable operation use a stator winding of the "Monolith" or "Monolith-2" type with a heat resistance class of at least "B". The body of the electric motors is reinforced, which in turn reduces sound and vibration levels. Specific material consumption and energy performance are in the optimal ratio. High-voltage electric motors are also characterized by increased wear resistance.
The following electric motors are intended for the drive:
- mechanisms that do not require speed control - series A4, A4 12 and 13, DAZO4, DAZO4-12, DAZO4-13, AOD, AOVM, AOM, DAV;
- mechanisms with difficult starting conditions - series 2AOD;
- vertical hydraulic pumps- DVAN series.
High-speed electric motors and their features
Unlike high voltage motors, high-speed - these are engines whose number of revolutions is 50 rpm or 3000 rpm. They have less weight, dimensions and even cost than slower counterparts of the same power.
To use engines with a frequency of up to 9000 rpm, it is necessary to use a mechanism with a large gear ratio, in particular, the wave transmission mechanism. It is simple, high reliability, accuracy and compactness.
The scope of high-speed engines is very wide. This includes electric motors for a hand-held engraver, and for a drill drill, and motors for the automotive and aviation industries.
Powerful electric motors
Ordinary three-phase electric motors rated power ranges from 120 W-315 kW. However, as practice shows, more powerful electric motor, the greater the height of the axis of the shaft. Therefore, it is customary to consider electric motors larger than 11 kW as powerful. The areas of application are also quite wide. In particular, crane and metallurgical. Electric motors high power also used in pumping units.
When grinding small diameter holes, it takes a lot of high speeds rotation of the grinding spindles. So, when grinding holes with a diameter of 5 mm on a wheel with a diameter of 3 mm at a speed of only 30 m / s, the spindle must have a rotation speed of 200,000 rpm.
The use of belt drives to increase the speed is limited to the maximum allowable speeds belt. Belt-driven spindle speeds typically do not exceed 10,000 rpm, and the belts slip, fail quickly (after 150-300 hours) and create vibrations during operation.
High-speed pneumatic turbines are also not always suitable due to the very significant softness of their mechanical characteristics.
The problem of creating high-speed spindles has special meaning for production ball bearings where high quality internal and groove grinding is required. In this regard, numerous models of so-called electrospindles with rotation speeds of 12,000-50,000 rpm and more are used in the machine tool and ball bearing industries.
The electrospindle (fig. 1) is a grinding spindle with three bearings and an integrated squirrel-cage high-frequency motor. The motor rotor is placed between two spores at the end of the spindle opposite the grinding wheel.
Less commonly used designs with two or four supports. In the latter case, the motor shaft is connected to the spindle by means of a clutch.
The motor stator of the electrospindle is assembled from electrotechnical sheet steel. It has a bipolar winding. The motor rotor at rotation speeds up to 30-50 thousand rpm is also recruited from sheet steel and is supplied with a conventional short-circuited winding. Rotor diameter tends to be as small as possible.
At speeds greater than 50,000 rpm, due to significant steel losses, the stator is provided with a jacket with running water cooling. The rotors of engines designed to operate at such speeds are made in the form of a solid steel cylinder.
Of particular importance for the operation of electrospindles is the choice of the type of bearings. At rotation speeds up to -50,000 rpm, high-precision ball bearings are used. Such bearings must have a maximum clearance not exceeding 30 microns, which is achieved by proper assembly. The bearings are preloaded with calibrated springs. The calibration of preload springs for ball bearings and the selection of their fit must be given great attention.
At rotation speeds greater than 50,000 rpm, plain bearings work satisfactorily when they are intensively cooled by flowing oil supplied by a special pump. Sometimes the lubricant is supplied in a sprayed state.
High-frequency electrospindles for 100,000 rpm were also built on aerodynamic bearings (air-lubricated bearings).
In the production of high-frequency electric motors, very precise manufacturing is required. individual parts, dynamic balancing rotor, precise assembly and ensuring a strict uniformity of the gap between the stator and the rotor.
In connection with the above, the manufacture of electrospindles is carried out according to special technical conditions.
Fig.1. High frequency grinding electrospindle.
Coefficient useful action high-frequency motors are relatively small. This is due to the presence of increased losses in steel and friction losses in bearings.
The dimensions and weight of high-frequency motors are relatively small.
Rice. 2. Modern high frequency electrospindle
The use of electric spindles instead of belt-driven drives in the production of ball bearings increases labor productivity when working on internal grinding machines by at least 15-20%, sharply reduces rejection in taper, ovality and surface finish. The durability of grinding spindles increases by 5-10 times or more.
Of great interest is also the use of high-speed spindles when drilling holes with a diameter of less than 1 mm.
The frequency of the current supplying the high-frequency motor is selected depending on the required rotation speed n of the motor according to the formula
since p = 1.
So, at speeds of rotation of electrospindles of 12,000 and 120,000 rpm, frequencies of 200 and 2000 Hz are required, respectively.
To power high-frequency motors, special high-frequency generators were previously used. Now, for these purposes, static frequency converters on high-speed field-effect transistors are used.
On fig. 3 shows a three-phase current synchronous induction generator domestic production(type GIS-1). As can be seen from the drawing, the stator of such a generator has wide and narrow grooves. The excitation winding, the coils of which are placed in the wide slots of the stator, is fed with direct current. The magnetic field of these coils is closed through the teeth of the stator and the protrusions of the rotor, as shown in Fig. 3 dotted.
Rice. 3. High frequency induction current generator.
When the rotor rotates, the magnetic field, moving along with the protrusions of the rotor, crosses the turns of the alternating current winding placed in the narrow grooves of the stator, and induces a variable e in them. d.s. The frequency of this e. d.s. depends on the speed of rotation and the number of protrusions of the rotor. electromotive forces, induced by the same flux in the coils of the excitation winding, are mutually compensated due to the counter-connection of the coils.
The excitation winding is powered through a selenium rectifier connected to the AC mains. Both the stator and the rotor have magnetic cores made of sheet steel.
Generators of the described design are manufactured for rated power of 1.5; 3 and 6 kW and at frequencies of 400, 600, 800 and 1200 Hz. The rated rotation speed of synchronous generators is 3000 rpm.
In everyday life, utilities, in any production, electric motors are an integral part: pumps, air conditioners, fans, etc. Therefore, it is important to know the types of the most common electric motors.
An electric motor is a machine that converts electrical energy into mechanical energy. This generates heat, which is a side effect.
Video: Classification of electric motors
All electric motors can be divided into two large groups:
- DC motors
- AC motors.
Electric motors powered by alternating current are called alternating current motors, which have two varieties:
- Synchronous- these are those in which the rotor and the magnetic field of the supply voltage rotate synchronously.
- Asynchronous. They have a different rotor speed from the frequency generated by the supply voltage magnetic field. They are multi-phase, as well as one-, two- and three-phase.
- Stepper motors are distinguished by the fact that they have a finite number of rotor positions. The fixed position of the rotor occurs due to the supply of power to a certain winding. By removing the voltage from one winding and transferring it to another, a transition is made to another position.
DC motors are those that are powered by direct current. They, depending on whether or not they have a brush-collector assembly, are divided into:
Collector also, depending on the type of excitation, there are several types:
- Excited by permanent magnets.
- WITH parallel connection connection and armature windings.
- With series connection of armature and windings.
- With their mixed connection.
Cross section of a DC motor. Collector with brushes - right
Which electric motors are included in the group "DC motors"
As already mentioned, DC motors make up a group that includes collector and brushless motors, which are made in the form of a closed system, including a rotor position sensor, a control system and a power semiconductor converter. Principle of operation brushless motors similar to the principle of operation of asynchronous motors. Install them in household appliances, such as fans.
What is a collector motor
The length of the DC motor depends on the class. For example, if we are talking about a class 400 engine, then its length will be 40 mm. The difference between collector electric motors and brushless counterparts is ease of manufacture and operation, therefore, its cost will be lower. Their feature is the presence of a brush-collector assembly, with the help of which the rotor circuit is connected to the circuits located in the stationary part of the motor. It consists of contacts located on the rotor - a collector and brushes pressed against it, located outside the rotor.
Rotor
These electric motors are used in radio-controlled toys: by applying voltage to the contacts of such an engine from a DC source (the same battery), the shaft is set in motion. And to change its direction of rotation, it is enough to change the polarity of the supplied supply voltage. Light weight and dimensions low price and the ability to restore the brush-collector mechanism make these motors the most used in budget models, despite the fact that it is significantly inferior in reliability to the brushless one, since sparking is not excluded, i.e. excessive heating moving contacts and their rapid wear when exposed to dust, dirt or moisture.
As a rule, a marking indicating the number of revolutions is applied to the collector electric motor: the smaller it is, the greater the shaft rotation speed. By the way, it is very smoothly adjustable. But, there are also high-speed engines of this type, not inferior to brushless ones.
Advantages and disadvantages of brushless motors
Unlike those described, for these electric motors, the movable part is a stator with permanent magnet(housing), and the rotor with a three-phase winding is stationary.
The disadvantages of these DC motors include less smooth adjustment of the shaft speed, but they are able to gain maximum speed in a split second.
The brushless motor is placed in a closed case, so it is more reliable when adverse conditions operation, i.e. he is not afraid of dust and moisture. In addition, its reliability is increased due to the absence of brushes, as is the speed at which the shaft rotates. At the same time, the design of the motor is more complex, therefore, it cannot be cheap. Its cost in comparison with the collector is twice as high.
Thus, a collector motor operating on alternating and direct current is versatile, reliable, but more expensive. It is both lighter and smaller than an AC motor of the same power.
Since AC motors powered by 50 Hz (commercial power supply) do not allow high frequencies(above 3000 rpm), if necessary, use a collector motor.
Meanwhile, its resource is lower than that of asynchronous electric motors alternating current, which depends on the condition of the bearings and the insulation of the windings.
How a synchronous motor works
Synchronous machines are often used as generators. It works synchronously with the mains frequency, so it is with an inverter and rotor position sensor, it is an electronic analogue collector electric motor direct current.
The structure of a synchronous motor
Properties
These engines are not self-starting mechanisms, but require external influence in order to pick up speed. They found application in compressors, pumps, rolling machines and similar equipment, working speed which does not exceed five hundred revolutions per minute, but an increase in power is required. They are quite large in size, have a "decent" weight and a high price.
Run synchronous motor can be done in several ways:
- Using external source current.
- The start is asynchronous.
In the first case, with the help of an auxiliary motor, which can be a DC electric motor or an induction motor three-phase motor. Initially, DC current is not supplied to the motor. It begins to rotate, reaching close to synchronous speed. At this moment it is served D.C.. After closing the magnetic field, the connection with the auxiliary motor is broken.
In the second option, it is necessary to install an additional short-circuited winding in the pole pieces of the rotor, crossing which the magnetic rotating field induces currents in it. They, interacting with the stator field, rotate the rotor. Until it reaches synchronous speed. From this point on, the torque and EMF decrease, the magnetic field closes, nullifying the torque.
These electric motors are less sensitive than asynchronous ones to voltage fluctuations, they have a high overload capacity, they keep the speed unchanged under any load on the shaft.
Single-phase electric motor: device and principle of operation
After starting, using only one stator winding (phase) and not needing a private converter, an electric motor operating from a single-phase alternating current mains is asynchronous or single-phase.
A single-phase electric motor has a rotating part - the rotor and a stationary part - the stator, which creates the magnetic field necessary for the rotation of the rotor.
Of the two windings located in the stator core to each other at an angle of 90 degrees, the working one occupies 2/3 of the grooves. Another winding, which accounts for 1/3 of the grooves, is called the starting (auxiliary).
The rotor is also a short-circuited winding. Its rods made of aluminum or copper are closed at the ends with a ring, and the space between them is filled with aluminum alloy. The rotor can be made in the form of a hollow ferromagnetic or non-magnetic cylinder.
Single phase motor, whose power can be from tens of watts to tens of kilowatts, are used in household appliances, installed in woodworking machines, on conveyors, in compressors and pumps. Their advantage is the possibility of using them in rooms where there is no three-phase network. By design, they do not differ much from three-phase asynchronous electric motors.
9000 rpm
They say it's the most cool car in history Lexus. And that his successor is obliged to jump through the roof, so as not to shame the legacy. They say that the sound of his motor can be listened to instead of music and instantly recognized even from a kilometer away. These enthusiastic fan epithets are about the LFA, the first full-fledged supercar from Lexus.
Dynamics Lexus LFA maybe not the most outstanding: acceleration to 100 km / h in 3.7 seconds, maximum speed- 326 km / h. But the car for its short life set a lot of records on the tracks (for example, at the Nurburgring) and "tacked" a lot of eminent rivals in drag battles. But the bright life of the LFA was short: in two years only 500 cars were made. No wonder fans are so excited for the sequel...
The car was built according to familiar canons: more aluminum (35%), more carbon (65%) ... But the hand-assembled engine turned out to be unique. Co-designed with Yamaha, the 4.8-liter V10, with its unusual 72-degree camber angle, was smaller than a conventional V8 and weighed less than a typical V6. Forged pistons, titanium connecting rods, valves and muffler, separate throttle for each cylinder, 560 hp. - and the "ceiling" at 9000 rpm! Moreover, Japanese engineers also separately tuned the "voice" of the engine, so that it was like that of Formula 1 cars. And it turned out: high revs LFA screams in a purely formulaic way!
Porsche 911 (991) GT3
Porsche 918 Spyder
9000 rpm
9150 rpm
IN big family Porsche, you will find several models whose engines seem to be about to go haywire from their own speed. The first is the 911 (991) GT3, produced since 2013. The six-cylinder boxer with a volume of 3.8 liters produces 475 hp. and spins up to 9000 rpm - thanks to almost weightless titanium connecting rods and forged pistons. Just because of the low-quality bolts of these very connecting rods, 785 cars fell under the revocable company. But every cloud has a silver lining: the company did not bother with replacing bolts - and simply put new engines on sports cars!
From November 2013 to June 2015, Porsche produced 918 Spyders in an edition of 918 units, each costing under a million euros. But, as you understand, the company had no problems with sales.
The second model, called the 918 Spyder, is already hybrid, three-engine and even crazier. The "heart" of the most-very Porsche in history is a 4.6-liter naturally aspirated V8 with a return of 608 Horse power and "cut-off" at 9150 rpm! And each axle here additionally turns its own electric motor. In total, it turned out 887 hp. and 1280 Nm of thrust (this is more than the more powerful LaFerrari), acceleration to 100 km / h in 2.5 seconds and a top speed of 351 km / h. Well, then - a minute of irresistible boasting: we managed to test the potential of this monster ourselves! you can read the text version of the test drive, and below we have posted the AutoVesti video for TV.
Ferrari LaFerrari
9250 rpm
The already legendary LaFerrari definitely deserves the title of the craziest Ferrari. The most powerful. The most advanced. And the very first hybrid model in the history of the company. From such blasphemy (exchange power clean energy atmospheric ICE on a cross between a goddess and an electric golf cart!) himself Enzo Ferrari probably rolled over in his grave. And at the same time, LaFerrari combined the difficult to combine.
Only 499 lucky people were able to buy a LaFerrari, paying over a million dollars for it.
Almost entirely molded from carbon fiber and equipped with carbon-ceramic brakes, it turned out to be airy light - only 1.2 tons of dry weight. active aerodynamics, active suspension, active rear "diff" ... And more than an active 800-horsepower motor that can spin up to 9250 rpm. But this is not some kind of motor with a cam, but a hefty atmospheric V12 with a volume of 6.2 liters! Plus a 163-horsepower electric motor built into the 7-speed "robot". At the output - 350 km / h "maximum speed" and acceleration to 100 km / h in about 2.5 seconds. And the LaFerrari not only drives crazy, it still sounds as crazy as a Ferrari should. If old Enzo had listened and tried, he would have forgiven and become proud...
10,000 rpm
Honda ate the dog on "twisting" motors - thanks to their motorcycle heritage! Many of you probably remember the crazy S2000 roadster with a 2-liter naturally aspirated engine that produced 240 hp. and spinning up to almost 9000 rpm. But who remembers the ideological ancestor of this machine?
The Honda S800 was produced from 1966 to 1970, making 11,536 units.
His name was S800. Lightweight, sleek and sporty two-seat roadster or coupe. Four cylinders, a working volume of only 0.8 liters. The motor gave out only 70 hp, but firstly, with it, the S800 became the first Honda, which accelerated to 160 km / h. And at that time it was the world's fastest production car with an engine up to 1 liter. And the engine itself accelerated to 10,000 rpm, and even with such a sound! It's funny that at the same time, the early S800s still combined very advanced in those years independent suspension in a circle - and chain drive rear drive wheels. Also a motorcycle heritage ...
