When using an electric motor in tools, one of the major problems is adjusting the speed of their rotation. If the speed is not fast enough, then the action of the tool is not effective enough.

If it is excessively high, then this leads not only to a significant waste of electrical energy, but also to a possible burnout of the tool. If the rotation speed is too high, the tool may also become less predictable. How to fix it? For this purpose, it is customary to use a special speed controller.

An engine for power tools and household appliances usually falls into one of 2 main types:

1. collector motors.
2. asynchronous motors.

In the past, the second of these categories was the most common. Now, approximately 85% of the motors that are used in electric tools, household or kitchen appliances are of the commutator type. This is explained by the fact that they have a greater degree of compactness, they are more powerful and the process of controlling them is simpler.

The operation of any electric motor is built on a very simple principle: if a rectangular frame is placed between the poles of the magnet, which can rotate around its axis, and a direct current is passed through it, then the frame will rotate. The direction of rotation is determined according to the “right hand rule”.

This pattern can be used to operate a collector engine.

The important point here is to connect the current to this frame. Since it rotates, special sliding contacts are used for this. After the frame rotates 180 degrees, the current through these contacts will flow in the opposite direction. Thus, the direction of rotation will remain the same. In this case, smooth rotation will not work. To achieve this effect, it is customary to use several dozen frames.

Device

The collector motor usually consists of a rotor (armature), a stator, brushes and a tachogenerator:

1. Rotor is the rotating part, the stator is the outer magnet.
2. Graphite brushes- this is the main part of the sliding contacts, through which voltage is applied to the rotating armature.
3. Tachogenerator is a device that monitors the characteristics of rotation. In the event of a violation of the uniformity of movement, it corrects the voltage supplied to the engine, thereby making it smoother.
4. stator may contain more than one magnet, but, for example, 2 (2 pairs of poles). Also, instead of static magnets, coils of electromagnets can be used here. Such a motor can work both from direct and from alternating current.

The ease of adjusting the speed of the collector motor is determined by the fact that the rotation speed directly depends on the magnitude of the applied voltage.

In addition, an important feature is that the axis of rotation can be directly attached to a rotating tool without the use of intermediate mechanisms.

If we talk about their classification, then we can talk about:

1. collector engines direct current.
2. collector engines alternating current.

In this case, we are talking about exactly what current the electric motors are powered by.

Classification can also be made according to the principle of motor excitation. In a collector motor device, electrical power is supplied to both the rotor and the stator of the motor (if it uses electromagnets).

The difference is how these connections are organized.

Here it is customary to distinguish:

• parallel excitement.
• Consistent arousal.
• Parallel-serial excitation.

Adjustment

Now let's talk about how you can adjust the speed of collector engines. Due to the fact that the speed of rotation of the motor simply depends on the amount of voltage applied, then any means of adjustment that can perform this function is quite suitable for this.

Here are some examples of such options:

1. Laboratory autotransformer(LATR).
2. Factory adjustment boards used in household appliances (you can use in particular those used in mixers or vacuum cleaners).
3. Buttons used in the design of power tools.
4. Household regulators lighting with smooth action.

However, all of the above methods have a very important flaw. Along with the decrease in speed, the power of the motor also decreases. In some cases, it can even be stopped with just a hand. In some cases, this may be acceptable, but for the most part, it is a major hurdle.

A good option is to perform speed control through the use of a tachogenerator. It is usually installed at the factory. In the event of deviations in the motor speed, an already corrected power supply corresponding to the desired speed is transferred to the motor. If the motor rotation control is built into this circuit, then there will be no power loss here.

What does it look like constructively? The most common rheostat adjustment of rotation, and made on the basis of the use of semiconductors.

In the first case, we are talking about a variable resistance with mechanical adjustment. It is connected in series to the collector motor. The disadvantage is additional heat generation and additional waste of battery life. With this method of adjustment, there is a loss of motor rotation power. Is a cheap solution. Not applicable for sufficiently powerful motors for the reasons mentioned.

In the second case, when using semiconductors, the motor is controlled by applying certain impulses. The circuit can change the duration of such pulses, which in turn changes the rotation speed without losing power.

How to make with your own hands?

There are various options for adjustment schemes. Let's take a look at one of them in more detail.

Here is the scheme of his work:

Initially, this device was developed to adjust the commutator motor on electric vehicles. It was about one where the supply voltage is 24 V, but this design is applicable to other motors.

The weak point of the circuit, which was determined during testing of its operation, is poor suitability at very high currents. This is due to some slowdown in the operation of the transistor elements of the circuit.

It is recommended that the current be no more than 70 A. There is no current and temperature protection in this circuit, so it is recommended to build in an ammeter and monitor the current visually. The switching frequency will be 5 kHz, it is determined by the 20 nF capacitor C2.

By changing the current strength, this frequency can change between 3 kHz and 5 kHz. Variable resistor R2 is used to regulate the current. When using the electric motor in a domestic environment, it is recommended to use a standard type regulator.

At the same time, it is recommended to choose the value of R1 in such a way as to correctly adjust the operation of the regulator. From the output of the microcircuit, the control pulse is fed to a push-pull amplifier based on transistors KT815 and KT816, then it goes to transistors.

The printed circuit board has a size of 50 by 50 mm and is made of one-sided fiberglass:

In this diagram, 2 resistors of 45 ohms are additionally indicated. This is done in order to possibly connect a conventional computer fan to cool the device. When using an electric motor as a load, it is necessary to block the circuit with a blocking (snubber) diode, which, according to its characteristics, corresponds to a double value of the load current and a double value of the supply voltage.

Operation of the device in the absence of such a diode can lead to damage due to possible overheating. In this case, the diode will need to be placed on the heat sink. To do this, you can use a metal plate, which has an area of ​​​​30 cm2.

Regulating keys work in such a way that the power loss on them is quite small. IN original circuit, a standard computer fan was used. To connect it, a limiting resistance of 100 ohms and a supply voltage of 24 V were used.

The assembled device looks like this:

When manufacturing a power unit (in the lower figure), the wires must be connected in such a way that there is a minimum of bends in those conductors through which large currents pass. We see that the manufacture of such a device requires certain professional knowledge and skills. Perhaps in some cases it makes sense to use a purchased device.

Selection criteria and cost

In order to correctly choose the most suitable type of regulator, you need to have a good idea of ​​what varieties of such devices are:

1. Various types of control. Can be vector or scalar control system. The former are used more often, while the latter are considered more reliable.
2. Regulator power should correspond to the maximum possible power of the motor.
3. By voltage it is convenient to choose a device that has the most versatile properties.
4. Frequency characteristics. The regulator that suits you should match the highest frequency that the motor uses.
5. Other characteristics. Here we are talking about the size of the warranty period, dimensions and other characteristics.

Depending on the purpose and consumer properties, prices for regulators can vary significantly.

For the most part, they are in the range from about 3.5 thousand rubles to 9 thousand:

1. Speed ​​controller KA-18 ESC, designed for 1:10 scale models. It costs 6890 rubles.
2. Speed ​​controller MEGA collector (waterproof). It costs 3605 rubles.
3. Speed ​​regulator for LaTrax 1:18 models. Its price is 5690 rubles.

Hello my dear readers. You probably noticed that many “somodelkins” often began to meet collector electric motors from automatic washing machines. But they are in no hurry to put such engines on their devices, not because they don’t know how to connect, but because not everyone knows how such engines drive under load, whether it is possible to adjust the engine speed. If it is possible to regulate the speed, then how, and whether the power of the collector electric motor decreases. And if it falls, then how to achieve it in order to maintain the power of the electric motor during speed control, etc. So today we’ll talk about how to properly connect collector electric motors from washing machines, and consider how such motors behave under load and how they are regulated rpm of this engine.

First of all, it is a single-phase collector electric motor with series excitation of the windings. To operate this type of motor, both alternating and direct current can be used - and therefore they can be considered universal. Despite the different appearance they have the same device. They consist of a stator with an excitation winding, an armature, brushes, a housing and a tachogenerator. A terminal block is used to output all wires.

The operation of this type of electric motor is based on the interaction of the magnetic fields of the stator and armature when an electric current passes through them.

To make the simplest connection, you can only know the outputs of the stator and armature windings. But how to find out where are the outputs on the terminal block, if their number can reach 10. To do this, we take a regular tester,

We put the regulator knob in the position of least resistance, and we begin to call the windings of the tachogenerator (tachometer), stator and armature (winding resistance from 3 to 200 ohms). I had a motor at hand with 6 leads to terminal blocks with 2 ohm resistances (stator); 4.4 ohm (armature); 165 Ohm (tachogenerator).

Now you need to determine where the tachogenerator outputs are located, for this you need to take the same tester, turn its knob to the variable voltage position and connect it to the terminals that ring among themselves, turning the armature by hand, on the tachogenerator terminals when turning the armature, the tester will show the presence of voltage.

Be careful, on engines, instead of a tachogenerator (two outputs), a Hall sensor is sometimes used (three outputs, determined by the tester at the position of least resistance, the tester first shows some resistance, and then it disappears). The armature leads are determined by ringing between the collector itself and the terminals on the block. Stator by elimination. The connection diagram using the terminal block looks like this: we put a jumper between one of the stator and armature terminals, and we apply voltage to the remaining two terminals. If you are sure that the electric motor from the washing machine is in perfect order, you can connect it directly to the network, and if you are not sure about the origin of the electric motor, then connect the engine in series with the simplest electric iron.

If, during connection, the collector motor slowly picks up speed, and there is no crackling during operation, there is no strong sparking on the brushes - this means that the collector motor is completely ready for operation and can be connected to a 220 Volt network.
And so, having directly connected the engine to the network with a tachometer, we check the speed (it showed more than 12000 rpm for me), after which we try to give it a load (for the load I used a piece of board which pressed on the motor shaft).

I didn’t manage to crush such an engine (the board started to burn), and the speed at the same time fell by half.

There are many ways to adjust the speed on collector electric motors, the speed can be adjusted using LATR, speed control boards from household appliances (vacuum cleaners, mixers, etc.), buttons from power tools, a lighting timer (dimmer) in general, all devices that regulate voltage.

We see that the speed is easily regulated when the voltage changes with such devices. With this connection, a significant drawback appears as a large drop in engine power (at a speed of 600 rpm, the shaft is easily stopped by hand).

Such speed control is not always suitable (it will do for fans and pumps) for widespread use for home-made machines and various devices. In this case, the tachogenerator, which is installed on the engine from the washing machine, will come to our aid. Which will report the number of revolutions of the armature, and transfer them to the microcircuit, and that, in turn, will regulate the power and revolutions of the engine through the triac. Here is an example of a circuit that can be easily repeated at home (more details about the circuit here http://shenrok.blogspot.com/p/blog-page_8.html):

Based on the powerful triac BT138-600, you can assemble an AC motor speed controller circuit. This circuit is designed to control the speed of rotation of the electric motors of drilling machines, fans, vacuum cleaners, angle grinders, etc. The motor speed can be adjusted by changing the resistance of the potentiometer P1. Parameter P1 determines the phase of the trigger pulse that opens the triac. The circuit also performs a stabilization function that maintains the speed of the motor even when it is heavily loaded.

For example, when the motor of a drilling machine slows down due to increased metal resistance, the EMF of the motor also decreases. This leads to an increase in voltage in R2-P1 and C3 causing the triac to open longer and the speed increases accordingly.

Regulator for DC motor

The simplest and most popular method for adjusting the speed of rotation of a DC motor is based on the use of pulse width modulation ( PWM or PWM ). In this case, the supply voltage is applied to the motor in the form of pulses. The pulse repetition rate remains constant, and their duration can change - this is how the speed (power) changes.

To generate a PWM signal, you can take a circuit based on the NE555 chip. The simplest DC motor speed controller circuit is shown in the figure:

Here VT1 is an n-type field effect transistor capable of withstanding the maximum motor current at a given voltage and load on the shaft. VCC1 is 5 to 16V, VCC2 is greater than or equal to VCC1. The frequency of the PWM signal can be calculated using the formula:

F = 1.44/(R1*C1), [Hz]

where R1 is in ohms, C1 is in farads.

With the ratings indicated in the diagram above, the PWM signal frequency will be equal to:

F = 1.44/(50000*0.0000001) = 290 Hz.

It is worth noting that even modern devices, including high-power control, are based on just such schemes. Naturally, using more powerful elements that can withstand high currents.

Adjustment of turns of electric motors

You have to deal with the issue of adjusting the speed when working with power tools, driving sewing machines and other appliances in everyday life and at work. Regulating speed by simply lowering the supply voltage does not make sense - the electric motor sharply reduces speed, loses power and stops. The best option for adjusting speed is voltage regulation. with motor load current feedback In most cases, electric tools and other devices use universal collector electric motors with series excitation. They work well on both AC and DC. A feature of the operation of a collector electric motor is that when the armature windings are switched on the collector lamellas, counter-EMF pulses of self-induction occur during opening. They are equal in amplitude but opposite in phase. The offset angle of the back EMF is determined by the external characteristics of the motor, its load and other factors. The harmful effect of back-EMF is expressed in sparking on the collector, loss of motor power, additional heating of the windings. Some of the back EMF is damped by the capacitors shunting the brush assembly.

Consider the processes occurring in the control mode with OS, using the example of a universal circuit (Fig. 1). Resistive-capacitive circuit R2-R3-C2 provides the formation of a reference voltage that determines the speed of rotation of the motor. When the load increases, the speed of rotation of the electric motor decreases, and its torque decreases. The back EMF that occurs on the electric motor and applied between the cathode of the thyristor VS1 and its control electrode is reduced. As a result, the voltage at the control electrode of the thyristor increases in proportion to the decrease in back-emf. The additional voltage on the control electrode of the thyristor causes it to turn on at a smaller phase angle (cutoff angle) and pass more current to the electric motor, thereby compensating for the decrease in rotation speed under load. There is, as it were, a balance of the impulse voltage on the control electrode of the thyristor, which is composed of the supply voltage and the self-induction voltage of the motor. Switch SA1 allows, if necessary, to switch to full voltage supply, without adjustment

The second scheme (Fig. 2) is designed for more powerful electric motors used in woodworking machines, grinders, drills. In it, the principle of regulation remains the same. The thyristor in this circuit should be installed on a radiator with an area of ​​​​at least 25 cm 2.

For low-power electric motors and, if necessary, to obtain very low rotation speeds, it is possible to successfully apply the circuit on the IC (Fig. 3). It is rated for 12 V DC power. In the case of a higher voltage, the microcircuit should be powered through a parametric stabilizer with a stabilization voltage not higher than 15V. Speed ​​control is carried out by changing the average value of the voltage of the pulses applied to the electric motor. Such impulses effectively regulate very low rotation speeds, as if continuously "pushing" the rotor of the electric motor. At high speeds, the motor runs normally.

A very simple scheme (Fig. 4) will help to avoid emergency situations on the (toy) railway line and open up new possibilities for managing trains. An incandescent lamp in an external circuit protects and signals a short circuit on the line, while limiting the output current.

When it is required to regulate the speed of electric motors with a large torque on the shaft, for example, in an electric winch, a full-wave bridge circuit (Fig. 5) can be useful, providing full power to the electric motor, which significantly differs from the previous ones, where only one half-wave of the supply voltage worked. Diodes VD2 and VD6 and a quenching resistor R2 are used to power the startup circuit. The delay in opening the thyristors in phase is provided by charging the capacitor C1 through resistors R3 and R4 from a voltage source, the level of which is determined by the zener diode VD8. When the capacitor C1 is charged to the threshold of operation of the unijunction transistor VT1, it opens and starts the thyristor, on the anode of which there is a positive voltage. When the capacitor discharges, the unijunction transistor turns off. The value of resistor R5 depends on the type of motor and the desired depth of feedback. Its value is calculated by the formula R5=2/Im, where Im is the effective value of the maximum load current for a given electric motor. one series).

Literature
1. Electronics Todays. Int N6
2.RCA Corp Manual
3.IOI Electronic Projects. 1977p93
5. G. E. Semiconductor Data Handbook 3. Ed
6. Count P. Electronic circuits. -M Mir, 1989
7. Semenov I. P. Power regulator with feedback. - Radio amateur, 1997, N12, C 21.

I.SEMENOV
Moscow region, Dubna
Radio amateur №10, 2000

Nowadays, no housewife can do without such a necessary appliance as a food processor in her kitchen. A variety of modifications allows you to perform any kitchen work without unnecessary effort and time. For example, a food processor with a meat grinder will allow you to cook delicious minced meat in just a few seconds, and a food processor with a dicing function will instantly cut products for your favorite salad. Therefore, each problem becomes a problem that requires an immediate solution.

To keep your food processor running for a long time, take good care of it.

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Major breakdowns of food processors

Combines come in three different types: mini, compact, and multifunctional. The latter type, for example, includes a food processor with a meat grinder and a juicer at the same time. But, despite their difference, the principle of operation of the food processor is almost the same for all modifications.

Various types of food processors

Getting into the processing bowl, the products are brought to the required state in accordance with the specified program, as the kenwood major classic km636 food processor does. The process takes place with the help of a variety of nozzles from whisks and discs to knives, which are installed at the bottom of the container or fixed on the lid. The nozzles are driven by a collector electric motor, whose power can vary from 300 W for mini-combines to 700 W, which a meat grinder has in its arsenal.

How to understand that the repair of the food processor has become an urgent need? Urgent action is required in several cases:

Possible causes of failure

Despite the variety of functions, any appliance, such as a kenwood food processor, consists of five main parts:

• engine;
• product receiver;
• capacity for processing products;
• set of knives and other attachments;
• control Panel.

The failure of any of them entails the main causes of the malfunction. They are both mechanical and electrical in nature.

Food processor parts can fail unexpectedly

The first variant of malfunctions is manifested in the fact that the rotational movement is not transmitted to the working body. This happens for one reason.

1. If a cooking assistant, such as a Mulinex food processor, has a belt drive, then the belt has broken.
2. When household appliances, such as a Philips food processor, have a direct drive, the lack of rotational movement indicates that the key on the rotor shaft has worn out.

Important! If the device runs unevenly, then the drive belt is loose and needs to be tightened. If this is no longer possible, a replacement part will be required.

Electrical problems can range from minor, such as blown fuse, switch or power cord, motor brush wear, to more serious when the motor fails and the armature needs to be rewound, commutator or control board replaced.

The combine does not work - what to do?

Sooner or later, owners of household appliances are faced with a situation where, after turning on, the unit either does not work at all, or does not work correctly, making various uncharacteristic noises and sometimes even sparkling. This fully applies to food processors.

In this case, the owner of the unit must remember whether the factory warranty still applies to the device. If the warranty period has not passed, then you must immediately contact the service center about the repair of your equipment.

When disassembling the food processor yourself, be sure to unplug it from the mains

If the guarantee for the kitchen assistant is no longer covered, then first try to understand the reasons for the breakdown yourself. To do this, you will need to disassemble the unit.

Important! When performing this operation, remember that you will then need to assemble the food processor back.

Here are the main dismantling steps:

1. disconnect the device from the mains and disconnect the removable elements;
2. remove the harvester from the base and turn over to inspect the drive belt and gear;
3. after removing the belt and gear, disconnect the engine, open it and inspect it;
4. remove the gearbox guard and inspect the drive shaft.

If necessary, more detailed advice for each specific model can be easily found on the Internet.

Having found out this aspect of the problem, and having identified a malfunction, make a decision to carry out repairs on your own or with the help of a professional.

If the combine still does not work, contact a repairman

If you understand electrical engineering and feel capable of self-repair, then here are some tips for this case.

• If the transmission belt is broken or loose, it must be replaced by purchasing a food processor belt from a service center.
• If the key is out of order, then more effort will be required: disassemble the combine by removing the motor; carefully dismantle the part; purchase a new key from the service center and install it in place.
• It will take you 5-10 minutes to replace a blown fuse. It is not worth it because of such smallness to waste time on a trip to the service.
• The connecting cord is also easy to replace on your own, since you can purchase the missing components in every electrical store.
• If there are problems with the gear, then first you need to properly clean it and carefully inspect it. A small percentage of wear is compensated by lubrication, in more difficult cases a replacement will be required.
• If the brush wears out, it is enough to replace the part with a new one.

Important! When purchasing spare parts, only purchase parts from the same manufacturer. Installing cheap parts will lead to the final breakdown of the combine.

Elimination of more serious breakdowns such as a burnt out motor, failure of a shaft or bearings should be entrusted to a specialist, if only because you do not have the necessary tools and tools at home.