Circuit for reducing electric motor speed. Typical food processor breakdowns: what to consider when repairing

Nowadays, not a single housewife can do without such a necessary device as a food processor in her kitchen. A variety of modifications allows you to perform without extra costs any amount of time and effort kitchen work. For example, a food processor with a meat grinder will allow you to prepare delicious minced meat in just a few seconds, and a food processor with a dicing function will instantly cut food for your favorite salad. Therefore, every problem becomes a problem that requires an immediate solution.

To ensure your food processor lasts a long time, take good care of it.

[content h2 h3]

Main breakdowns of food processors

There are three combine harvesters 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 differences, the principle of operation of a food processor is almost the same for all modifications.

Various types of food processors

Once in the processing bowl, the products are brought to the required state in accordance with a given program, just like the Kenwood major classic km636 food processor does. The process takes place using various attachments from whisks and discs to knives that are installed at the bottom of the container or attached to the lid. The attachments are driven by a commutator electric motor, whose power can vary from 300 W for mini-harvesters to 700 W, which a combine with a meat grinder has in its arsenal.

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

Possible causes of failure

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

• engine;
• food receptacle;
• container for processing products;
• a set of knives and other attachments;
• control Panel.

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

Food processor parts may fail unexpectedly

The first type of malfunction is manifested in the fact that rotational motion is not transmitted to the working element. This happens for one reason.

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

Important! If the device operates unevenly, it means that the drive belt is loose and needs to be tightened. If this is no longer possible, the part will need to be replaced.

Problems with the electrical part can be either minor, such as a blown fuse, switch or power cord, wear on the motor brush, or more serious, when the motor fails and requires rewinding the armature, replacing the commutator or control board.

The combine does not work - what to do?

Owners household appliances sooner or later they encounter a situation when, after switching on, the unit either does not work at all or does not work correctly, emitting 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 is still valid for the device. If the warranty period has not passed, you must immediately contact a service center to repair your equipment.

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

If the kitchen assistant is no longer covered by the warranty, 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, do not forget that you will then need to reassemble the food processor.

Here are the main stages of dismantling:

1. disconnect the device from the network and disconnect the removable elements;
2. remove the combine from the base and turn it over to inspect the drive belt and gear;
3. Having removed the belt and gear, disconnect the engine, open it and inspect it;
4. remove protective cover gearbox and inspect the drive shaft.

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

Having figured out this aspect of the problem and identified the 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 breaks or becomes loose, it must be replaced by purchasing a food processor belt from service center.
• If the key fails, 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’s not worth wasting time on a trip to the service center for such a small thing.
• The connecting cord is also easy to replace yourself, since you can purchase the missing components at any electrical store.
• If there are problems with the gear, then first you need to thoroughly clean it and carefully inspect it. A small percentage of wear is compensated by lubrication; in more complex cases, replacement will be required.
• When the brush wears out, it is enough to replace the part with a new one.

Important! When purchasing spare parts, purchase only parts from the same manufacturer. Installing cheap parts will lead to complete 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 equipment and tools at home.

A high-quality and reliable rotation speed controller for single-phase commutator electric motors can be made using common parts in literally 1 evening. This circuit has a built-in overload detection module, provides a soft start of the controlled motor and a motor rotation speed stabilizer. This unit operates with voltages of both 220 and 110 volts.

Regulator technical parameters

• supply voltage: 230 volts alternating current
• regulation range: 5…99%
• load voltage: 230 V / 12 A (2.5 kW with radiator)
• maximum power without radiator 300 W
• low noise level
• speed stabilization
• soft start
• board dimensions: 50×60 mm

Schematic diagram

The control system module circuit is based on a PWM pulse generator and a motor control triac - a classic circuit design for such devices. Elements D1 and R1 ensure that the supply voltage is limited to a value that is safe for powering the generator microcircuit. Capacitor C1 is responsible for filtering the supply voltage. Elements R3, R5 and P1 are a voltage divider with the ability to regulate it, which is used to set the amount of power supplied to the load. Thanks to the use of resistor R2, which is directly included in the supply circuit to the m/s phase, indoor units synchronized with triac VT139.

The following figure shows the arrangement of elements on printed circuit board. During installation and startup, attention should be paid to ensuring the conditions safe work— the regulator is powered from a 220V network and its elements are directly connected to the phase.

Increasing regulator power

In the test version, a BT138/800 triac with a maximum current of 12 A was used, which makes it possible to control a load of more than 2 kW. If you need to control even larger load currents, we recommend installing the thyristor outside the board on a large heatsink. You should also remember about making the right choice fuse FUSE depending on the load.

In addition to controlling the speed of electric motors, you can use the circuit to adjust the brightness of lamps without any modifications.

Thanks to global electrification, our lives have become more comfortable and cozy. Life modern man It’s impossible to imagine without electrical appliances. Many household appliances, which are entirely powered by electricity, are used in every home today. Even rural life abounds various devices, making the farm more progressive and less burdensome for its owner.

In this article we will touch on the topic of household electric motors that serve faithfully in our vacuum cleaners, in washing machines, in coffee grinders, in food processors, in microwave ovens, and in many others household appliances, using which we don’t even think about how they are designed and how important the role of the electric motor is in them.

Household electric motors are not multi-kilowatt industrial units, they are often the result of engineering work to optimize seemingly ordinary principles in order to reduce disadvantages to a minimum, and at the same time increase efficiency, in relation to a specific device. It is necessary that the engine be compact, as quiet as possible, and not consume too much electricity, while accurately performing the functions assigned to the household appliance.

Let's start with the kitchen. Every kitchen has a microwave. Some kitchens have a food processor, a coffee grinder, and even a dishwasher. Let's look at the engines of these devices.

Recirculation pump dishwasher designed to pump water into washing showers machine, has a small drive as a drive. The rotor speed is approximately 2800 rpm, and its power can be different - from 60 to 180 watts, usually, depending on the capacity of the dishwasher.

The motor winding is equipped with a parallel running capacitor, the typical capacitance of which is 3 µF. This engine copes with its task perfectly - it rotates the pump impeller and pumps water.

There are two motors in a microwave oven. The first one rotates turntable. Here you need a lot of power and low speeds, so this motor is synchronous, and although it is single-phase, it has a gear reducer. The rotor is a round permanent magnet that rotates at a speed of up to 3000 rpm, but the gearbox reduces the speed to 2.5 - 6 rpm, which is transmitted to the table.

The power of this small puck-shaped motor ranges from 2.5 to 5 watts, and the supply voltage can be 21, 30 or 220 volts, depending on the microwave model. This gear motor copes with its task of rotating a table with heavy dishes with a bang.

The microwave also has a fan for the magnetron cooling system. This fan is driven by a single-phase asynchronous motor, with a power of 10 to 50 watts, the rotor speed of which is 1200 - 1300 rpm. The engine stator is made of electrical steel plates, the rotor is simply a steel cylinder with a pressed-in shaft.

The working winding is made of thin enamel wire and is located on a plastic frame placed on the stator. There is also a starting winding, the role of which is played by short-circuited single turns of large cross-section, located at the edges of the stator, and forming the starting torque when turned on.

The motor is not very efficient, but it copes with its function - to rotate the fan and drive air through the magnetron radiator.

Coffee grinders use single-phase commutator motors. Such motors have windings on both the stator and the rotor. Through the commutator-brush assembly, power is supplied to the rotor windings, and the rotation speed of the coffee grinder blades is enormous.

The motors of typical home coffee grinders are powered by alternating current and have a power of up to 180 watts. They develop revolutions significantly exceeding 3000 per minute, and can reach 20,000 or more revolutions per minute, this is a feature of brushed motors.

The food processor is also equipped with a single-phase, but more powerful than coffee grinders. The power of the food processor engine can reach a kilowatt, and the speed here is regulated by means of a similar principle.

The advantage of a commutator motor in relation to a food processor is high torque and high maximum speed, since the motor is neither synchronous nor conventional asynchronous, its speed depends little on the frequency, and more on the average current.

Now let's move to the bathroom. There is, of course, an automatic washing machine. From the very beginning, they used commutator motors with thyristor speed control. This motor is equipped with a tachometer, which allows the electronics to accurately set the rotation speed of the washing machine drum at any load level.

The small pulley on the motor shaft is much smaller in diameter than the rotor, and at speeds reaching 10,000 rpm, 1000 rpm are transmitted to the drum through the belt, and the power can range from 200 to 800 watts.

More modern washing machines use direct drive motors and brushless asynchronous motors. As a rotor - an external rotor with 12 permanent magnets, and as a stator - an internal 36 coil stator. The coils are combined into three groups of 12 pieces, and allow for three-phase frequency control of the drum rotation speed (frequency up to 300 hertz) via an electronic BLDC controller, and power (rotation torque) via PWM control.

These motors are asynchronous and are controlled using a BLDC inverter, where a constant voltage of around 325 volts is pulsed sequentially to three groups of stator coils. The speed reaches 1500 rpm, and the power is around 1300 watts.

Next, of course, let's remember the vacuum cleaner. Motors for vacuum cleaners were initially always commutator motors. Here the revolutions are up to 10,000 per minute, and the power is up to 2 kilowatts. Such motors are loud due to the design of the turbine, which is driven into rotation.

The most advanced vacuum cleaners with pulsed magnetic motors, where permanent neodymium magnets are located on the rotor, reach 100,000 revolutions per minute, again due to BLDC - pulsed control technology. Such motors are a real miracle of engineering. The motor is integrated into the suction and filtration system, the operating power reaches 1300 watts, that is, such a motor in a vacuum cleaner works more efficiently than a collector motor.

Three-speed room fans operate on single-phase asynchronous AC motors with a power of 60 watts. These motors have four windings on the stator, connected in series with each other and with a capacitor with a capacity of 1.2 μF, although the motor is single-phase. The windings, connected in series to form a closed stator circuit, are combined into two parallel circuits in three different combinations when switching, so three different fan speeds are available.

So, we looked at ten household electric motors from the most commonly found household appliances. Of course, these are not all engines, there are also a variety of hair dryers, depilling machines, razors, looms, drills, screwdrivers, humidifiers (from the first), pumps for aquariums, sewing machines, printers and much more. If you list all the engines, even ten pages will not be enough.

We hope that this short review was useful to you, and you now know what electric motors work in your household appliances that you use every day, and maybe you didn’t even suspect that everything worked that way.

Andrey Povny

You have to deal with the problem of adjusting the speed of an electric motor quite often: this is working with various power tools, drives sewing machines, other electrical appliances in production and at home. Regulating the speed by lowering the supply voltage often makes no sense: the engine speed decreases sharply, it loses power and stops. That's why the best option to regulate the engine speed is to change the voltage using feedback by load current.

In most cases, power tools and other equipment use universal commutator motors with series excitation. They work equally well on both AC and DC power. The peculiarity of the operation of a commutator electric motor is that during commutation of the armature windings, when the commutator lamellas are opened, pulses of self-inductive back-EMF occur. They are equal in amplitude to the supply pulses, but in phase they are opposite to them. The angle of displacement of the back-EMF depends both on the external characteristics of the motor and on the load and other factors.

The harmful effect of back-EMF leads to sparking on the commutator, as well as loss of engine power and additional heating of its windings. Some of the back-EMF is suppressed by capacitors that bypass the brush assembly.

Let's look at the processes that occur in the feedback control mode, using the example of a universal circuit ( see fig. 1). The reference voltage, which determines the rotation speed of the electric motor, is formed by the resistive-capacitive circuit P12-KZ-S2. As the load increases, the rotation speed drops, and its torque also decreases. At the same time, the back-EMF that occurs in the engine and is applied between the cathode and the control electrode of thyristor VS1 also decreases. This leads to a change in voltage at the control electrode of the thyristor, which increases in proportion to how the back EMF decreases.

The additional voltage on the control electrode of the thyristor causes it to turn on at a smaller phase angle (cut-off angle) and supply more current to the motor, which thus compensates for the decrease in rotation speed as the load increases. This leads to the presence of a pulse voltage balance on the control electrode of the thyristor, which is composed of the supply voltage and the self-induction voltage of the motor.

If necessary, it is possible to use switch SA1 to switch to power supply using full voltage, without using adjustment. Particular attention must be paid to selecting a thyristor based on the minimum switching current, as this will ensure better stabilization of the motor rotation speed.

Second switching circuit ( see fig.2) is designed to work with more powerful engines that are used in grinding machines, woodworking machines and drills. The principle of regulation remains the same. The thyristor in this circuit must be installed on a radiator with an area of ​​at least 25 sq.cm.

If it is necessary to obtain very low rotation speeds or when used for low-power motors, you can use a circuit using an IC ( see fig. 3). It is powered by 12V DC. In case of power supply from more high voltage it is necessary to use a parametric stabilizer with a stabilization voltage no higher than 15V.

Speed ​​control is carried out by changing the average voltage of the pulses that are supplied to the engine. With the help of such pulses, it is possible to effectively regulate very low rotation speeds, since they seem to “push” the engine rotor. When the rotation speed increases, the engine operates normally.

Quite a simple scheme ( see fig. 4) is intended for use on a toy line railway. It will allow you to avoid emergency situations and will provide new opportunities for train management. The incandescent lamp, located in the external circuit, protects and serves to signal a short circuit on the line, while limiting the output current.

If it is necessary to regulate the speed of engines with a large torque on the shaft (for example, in an electric winch), a full-wave bridge circuit shown in Fig. 5. Its significant difference from previous schemes, where only one half-wave of the supply voltage operates, is the provision of full power to the engine.

Quenching resistor R2 and diodes VD2 and VD6 are used to supply power to the trigger circuit. The phase delay in opening the thyristors is ensured by charging capacitor C1 through resistors R3 and R4 from a voltage source, the level of which depends on the zener diode VD8. After charging the capacitor C1 to the operating threshold of the unijunction transistor VT1, the latter opens and starts the thyristor whose anode has a positive voltage. After the capacitor discharges, the unijunction transistor turns off. The value of resistor R5 is determined by the desired feedback depth and the type of motor. To calculate its value, the formula is used:

where Im is the effective value of the maximum load current for a given motor type.

The proposed schemes are easily repeated, but require the selection of certain elements depending on the characteristics of the electric motor used (unfortunately, it is almost impossible to find electric motors that are identical in all respects, even within the same series).

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

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

The motor for power tools and household appliances is usually one of 2 main types:

1. Commutator motors.
2. Asynchronous motors.

In the past, the second of these categories was most widespread. Now, approximately 85% of engines that are used in electrical instruments, household or kitchen appliances, belong to the collector type. This is explained by the fact that they are more compact, they are more powerful and the process of managing them is simpler.

The operation of any electric motor is based on a very simple principle: if you place a rectangular frame between the poles of a magnet, which can rotate around its axis, and move it along it D.C., 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 commutator motor.

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. At the same time, smooth rotation will not work. To achieve this effect, it is customary to use several dozen frames.

Device

A commutator motor usually consists of a rotor (armature), stator, brushes and tachogenerator:

1. Rotor- this is the rotating part, the stator is an external magnet.
2. Brushes made of graphite- this is the main part of the sliding contacts, through which voltage is supplied to the rotating armature.
3. Tachogenerator is a device that monitors rotation characteristics. In the event of a violation of the uniformity of movement, it adjusts the voltage supplied to the engine, thereby making it smoother.
4. Stator may contain not one magnet, but, for example, 2 (2 pairs of poles). Also, instead of static magnets, electromagnet coils can be used here. Such a motor can operate on both direct and alternating current.

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

Besides, important feature is that the rotation axis can be directly attached to rotating tools without the use of intermediate mechanisms.

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

1. Brushed motors direct current.
2. Brushed motors alternating current.

In this case, we are talking about what kind of current is used to power the electric motors.

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

The difference lies in how these connections are organized.

Here it is customary to distinguish:

• Parallel excitation.
• Consistent excitation.
• Parallel-sequential excitation.

Adjustment

Now let's talk about how you can regulate the speed of commutator motors. Due to the fact that the rotation speed of the motor simply depends on the amount of voltage supplied, any means of adjustment that are capable of performing this function are quite suitable for this.

Let's list a few of these options as examples:

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 engine power also decreases. In some cases, it can be stopped even just with your hand. In some cases, this may be acceptable, but in most cases, it is a serious obstacle.

A good option is to adjust the speed using a tachogenerator. It is usually installed at the factory. If there are deviations in the motor rotation speed, an already adjusted power supply corresponding to the required rotation speed is transmitted to the motor. If you integrate motor rotation control into this circuit, then there will be no loss of power.

How does this look constructively? The most common are rheostatic rotation control, and those made using semiconductors.

In the first case, we are talking about variable resistance with mechanical adjustment. It is connected in series to the commutator motor. The disadvantage is the additional heat generation and additional waste of battery life. With this adjustment method, there is a loss of engine 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 pulses. The circuit can change the duration of such pulses, which in turn changes the rotation speed without loss of power.

How to make it yourself?

Exist various options adjustment schemes. Let us present one of them in more detail.

Here is how it works:

Initially, this device was developed to adjust the commutator motor in electric vehicles. We were talking about one where the supply voltage is 24 V, but this design is also applicable to other engines.

The weak point of the circuit, which was determined during testing of its operation, is poor suitability for very large values current strength. 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 or 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 capacitor C2 with a capacity of 20 nf.

As the current changes, this frequency can change between 3 kHz and 5 kHz. Variable resistor R2 is used to regulate the current. When using an electric motor in living conditions, it is recommended to use a standard type regulator.

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

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

This diagram additionally shows 2 45 ohm resistors. This is done for the possible connection of a regular computer fan to cool the device. When using an electric motor as a load, it is necessary to block the circuit with a blocking (damper) diode, which in its characteristics corresponds to twice the load current and twice the supply voltage.

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

Regulating switches work in such a way that the power losses on them are quite small. IN In the original design, 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 bending of 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 regulator, you need to have a good idea of ​​what types of such devices there are:

1. Various types of control. Can be a vector or scalar control system. The former are used more often, while the latter are considered more reliable.
2. Regulator power must correspond to the maximum possible engine power.
3. By voltage It is convenient to choose a device that has the most universal 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 length 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 range from approximately 3.5 thousand rubles to 9 thousand:

1. Speed ​​controller KA-18 ESC, designed for 1:10 scale models. Costs 6890 rubles.
2. MEGA speed controller collector (moisture-proof). Costs 3605 rubles.
3. Speed ​​controller for LaTrax 1:18 models. Its price is 5690 rubles.