Description of the electric motor speed controller without loss of power. How to regulate engine speed from a washing machine Speed ​​control devices for brushed DC motors

The engine speed controller is needed to perform smooth acceleration and braking. Such devices have become widespread in modern industry. Thanks to them, the speed of movement in the conveyor, on various devices, as well as when the fan rotates, is measured. Motors with 12 Volt performance are used in entire control systems and in cars.

System design

Commutator motor type consists mainly of a rotor, a stator, as well as brushes and a tachogenerator.

1. The rotor is part of the rotation, the stator is an external type of magnet.
2. Brushes, which are made of graphite, are the main part of the sliding contact, through which voltage is applied to the rotating armature.
3. A tachogenerator is a device that monitors the rotation characteristics of the device. If there is a violation in the regularity of the rotation process, then it adjusts the voltage level entering the engine, thereby making it smoother and slower.
4. Stator. Such a part may include not one magnet, but, for example, two pairs of poles. At the same time, instead of static magnets, there will be coils of electromagnets. Such a device is capable of performing work both from direct current and alternating current.

Scheme of the speed controller of the commutator motor

Special frequency converters are used in the form of speed controllers for 220 V and 380 V electric motors . Such devices are classified as high-tech, they help to make a fundamental transformation of the current characteristics (signal shape, as well as frequency). They are equipped with powerful semiconductor transistors, as well as a pulse-width modulator. The entire process of operating the device occurs through the control of a special unit on a microcontroller. The change in speed in the rotation of the motor rotor occurs quite slowly.

It is for this reason that frequency converters are used in loaded devices. The slower the acceleration process occurs, the less load will be placed on the gearbox, as well as the conveyor. In all frequency generators you can find several degrees of protection: by load, current, voltage and other indicators.

Some models of frequency converters supply power from a single-phase voltage (it will reach 220 Volts) and create a three-phase voltage from it. This helps to connect an asynchronous motor at home without the use of particularly complex circuits and designs. In this case, the consumer will not lose power while working with such a device.

Why use such a device-regulator?

If we talk about regulator motors, then the revolutions needed are:

The circuits used to create frequency converters in an electric motor are widely used in most household devices. Such a system can be found in wireless power supplies, welding machines, phone chargers, power supplies for personal computers and laptops, voltage stabilizers, lamp ignition units for backlighting modern monitors, as well as LCD TVs.

220V electric motor speed controller

You can make it completely yourself, but for this you will need to study all possible technical features of the device. By design, several types of main parts can be distinguished. Namely:

1. The electric motor itself.
2. Microcontroller control system for the conversion unit.
3. Drive and mechanical parts that are associated with the operation of the system.

Just before starting the device, after applying a certain voltage to the windings, the process of rotating the engine begins with maximum power. It is this feature that will distinguish asynchronous devices from other types. On top of everything else, the load from the mechanisms that set the device in motion is added. Ultimately, at the initial stage of operation of the device, the power, as well as the current consumption, only increases to the maximum level.

At this time, the process of releasing the greatest amount of heat occurs. Overheating occurs in the windings, as well as in the wires. Using Partial Transformation will help prevent this from happening. If you install a soft start, then to the maximum speed mark (which can also be adjusted by equipment and may not be 1500 rpm, but only 1000), the engine will begin to accelerate not at the first moment of operation, but over the next 10 seconds (at the same time, every second the device will add 100-150 revolutions). At this time, the load on all mechanisms and wires begins to decrease several times.

How to make a regulator with your own hands

You can completely independently create an electric motor speed controller of about 12 V. For this you should use switch of several positions at once, as well as a special wirewound resistor. With the help of the latter, the supply voltage level changes (and at the same time the rotation speed indicator). The same systems can be used to perform asynchronous movements, but they will be less effective.

Many years ago, mechanical regulators were widely used - they were built on the basis of gear drives or their variators. But such devices were considered not very reliable. Electronic means showed themselves several times better, since they were not so large and allowed for finer adjustment of the drive.

In order to create an electric motor rotation controller, it is worth using several devices at once, which can either be bought at any hardware store or removed from old inventory devices. To complete the adjustment process, you should turn on special variable resistor circuit. With its help, the process of changing the amplitude of the signal entering the resistor occurs.

Implementation of a management system

To significantly improve the performance of even the simplest equipment, it is worth connecting microcontroller control to the engine speed controller circuit. To do this, you should choose a processor that has a suitable number of inputs and outputs, respectively: to connect sensors, buttons, and special electronic keys.

To carry out experiments you should use special microcontroller AtMega 128 is the easiest to use and widely used controller. In free use you can find a large number of schemes using it. In order for the device to perform the correct operation, a certain algorithm of actions should be written into it - responses to certain movements. For example, when the temperature reaches 60 degrees Celsius (the measurement will be noted on the graph of the device itself), the device should automatically turn off.

Operation adjustment

Now it’s worth talking about how you can adjust the speed in a brushed motor. Due to the fact that the overall speed of rotation of the motor can directly depend on the magnitude of the supplied voltage level, absolutely any control systems that can perform such a function are quite suitable for this.

It is worth listing several types of devices:

1. Laboratory autotransformers (LATR).
2. Factory control boards that are used in household devices (you can even take those that are used in vacuum cleaners and mixers).
3. Buttons that are used in the design of power tools.
4. Household types of regulators that are equipped with a special smooth action.

But at the same time, all such methods have a certain flaw. Together with the process of reducing speed, the overall power of the engine also decreases. Sometimes it can be stopped even by simply touching it with your hand. In some cases this may be quite normal, but for the most part it is considered a serious problem.

The most acceptable option would be to perform the function of adjusting the speed using tachogenerator applications.

It is most often installed at the factory. When the rotation speed of the motors deviates through the triacs in the motor, the already adjusted power supply will be transmitted, accompanying the desired rotation speed. If control of the rotation of the motor itself is built into such a container, then power will not be lost.

What does this look like in design? Most of all, it is the rheostat control of the rotation process, which is created based on the use of a semiconductor.

In the first case we will talk about variable resistance using a mechanical adjustment process. It will be connected in series to the commutator motor. The disadvantage in this case will be the additional release of some heat and an additional waste of the resource of the entire battery. During such an adjustment, a general loss of power occurs as the motor rotates. It is considered the most economical option. Not used for fairly powerful motors for the above reasons.

In the second case During the use of semiconductors, the process of controlling the motor occurs by applying a certain number of pulses. The circuit is capable of changing the duration of such pulses, which, in turn, will change the overall speed of rotation of the motor without loss of power.

If you do not want to manufacture equipment yourself, but want to buy a device that is completely ready for use, then you should pay special attention to the main parameters and characteristics, such as power, type of device control system, voltage in the device, frequency, and operating voltage . It would be best to calculate the general characteristics of the entire mechanism in which it is worth using a general motor voltage regulator. It is worth remembering that you need to make a comparison with the parameters of the frequency converter.

The electric motor is necessary for smooth acceleration and braking. Such devices are widely used in industry. With their help, the rotation speed of the fans is changed. 12 Volt motors are used in control systems and automobiles. Everyone has seen the switches that change the rotation speed of the stove fan in cars. This is one of the types of regulators. It's just not designed to run smoothly. The rotation speed changes in steps.

Application of frequency converters

Frequency converters are used as speed regulators and 380V. These are high-tech electronic devices that allow you to radically change the characteristics of the current (signal shape and frequency). They are based on powerful semiconductor transistors and a pulse-width modulator. All operation of the device is controlled by a microcontroller unit. The rotation speed of the engine rotor changes smoothly.

Therefore, they are used in loaded mechanisms. The slower the acceleration, the less load the conveyor or gearbox will experience. All frequencies are equipped with several degrees of protection - for current, load, voltage and others. Some models of frequency converters are powered from single-phase and turn it into three-phase. This allows you to connect asynchronous motors at home without using complex circuits. And there will be no loss of power when working with such a device.

For what purposes are regulators used?

In the case of asynchronous motors, speed controllers are needed for:

1. Significant energy savings. After all, not every mechanism requires a high motor rotation speed - sometimes it can be reduced by 20-30%, and this will reduce energy costs by half.
2. Protection of mechanisms and electronic circuits. Using frequency converters, you can control temperature, pressure and many other parameters. If the engine operates as a pump drive, then a pressure sensor must be installed in the container into which it pumps air or liquid. And when the maximum value is reached, the motor will simply turn off.
3. Performing a soft start. There is no need to use additional electronic devices - everything can be done by changing the settings of the frequency converter.
4. Reduced maintenance costs. With the help of such speed controllers for 220V electric motors, the risk of failure of the drive and individual mechanisms is reduced.

The circuit according to which frequency converters are built is widespread in many household appliances. Something similar can be found in uninterruptible power supplies, welding machines, voltage stabilizers, power supplies for computers, laptops, phone chargers, ignition units for backlight lamps of modern LCD TVs and monitors.

How do rotary controls work?

You can make an electric motor speed controller with your own hands, but to do this you will need to study all the technical aspects. Structurally, several main components can be distinguished, namely:

1. Electric motor.
2. Microcontroller control system and converter unit.
3. Drive and mechanisms associated with it.

At the very beginning of operation, after voltage is applied to the windings, the motor rotor rotates with maximum power. It is this feature that distinguishes asynchronous machines from others. To this is added the load from the mechanism that is driven. As a result, at the initial stage, power and current consumption increase to a maximum.

A lot of heat is generated. Both the windings and wires overheat. Using a frequency converter will help get rid of this. If you set a soft start, then the engine will not accelerate to maximum speed (which is also regulated by the device and may not be 1500 rpm, but only 1000) not immediately, but within 10 seconds (increase 100-150 rpm every second). At the same time, the load on all mechanisms and wires will decrease significantly.

Homemade regulator

You can make your own speed controller for a 12V electric motor. This will require a multi-position switch and wirewound resistors. With the help of the latter, the supply voltage (and with it the rotation speed) changes. Similar systems can be used for asynchronous motors, but they are less efficient. Many years ago, mechanical regulators were widely used - based on gear drives or variators. But they were not very reliable. Electronic means perform much better. After all, they are not so bulky and allow you to fine-tune the drive.

To make an electric motor rotation controller, you will need several electronic devices, which can either be purchased in a store or removed from old inverter devices. The VT138-600 triac shows good results in the circuits of such electronic devices. To make the adjustment, you will need to include a variable resistor in the circuit. With its help, the amplitude of the signal entering the triac changes.

Implementation of a management system

To improve the parameters of even the simplest device, you will need to include microcontroller control in the electric motor speed controller circuit. To do this, you need to select a processor with a suitable number of inputs and outputs - for connecting sensors, buttons, electronic keys. For experiments, you can use the AtMega128 microcontroller - the most popular and easiest to use. You can find many schemes using this controller in the public domain. Finding them yourself and applying them in practice is not difficult. In order for it to work correctly, you will need to write an algorithm into it - responses to certain actions. For example, when the temperature reaches 60 degrees (measured on the radiator of the device), the power should be turned off.

Finally

If you decide not to make a device yourself, but to purchase a ready-made one, then pay attention to the main parameters, such as power, type of control system, operating voltage, frequencies. It is advisable to calculate the characteristics of the mechanism in which it is planned to use the motor voltage regulator. And don’t forget to compare it with the parameters of the frequency converter.

You can adjust the rotation speed of the shaft of a low-power commutator motor by connecting it in series to its power supply circuit. But this option creates a very low efficiency, and in addition there is no possibility of smoothly changing the rotation speed.

The main thing is that this method sometimes leads to a complete stop of the electric motor at low supply voltage. Electric motor speed controller The DC circuits described in this article do not have these disadvantages. These circuits can also be successfully used to change the brightness of 12-volt incandescent lamps.

Description of 4 electric motor speed controller circuits

First scheme

The rotation speed is changed by variable resistor R5, which changes the duration of the pulses. Since the amplitude of the PWM pulses is constant and equal to the supply voltage of the electric motor, it never stops even at a very low rotation speed.

Second scheme

It is similar to the previous one, but the operational amplifier DA1 (K140UD7) is used as the master oscillator.

This op-amp functions as a voltage generator producing triangular-shaped pulses and having a frequency of 500 Hz. Variable resistor R7 sets the rotation speed of the electric motor.

Third scheme

It is unique, built on it. The master oscillator operates with a frequency of 500 Hz. The pulse width, and therefore the engine speed, can be changed from 2% to 98%.

The weak point in all the above schemes is that they do not have an element for stabilizing the rotation speed when the load on the DC motor shaft increases or decreases. You can resolve this problem using the following diagram:

Like most similar regulators, the circuit of this regulator has a master voltage generator that produces triangular pulses with a frequency of 2 kHz. The entire specificity of the circuit is the presence of positive feedback (POS) through elements R12, R11, VD1, C2, DA1.4, which stabilizes the rotation speed of the electric motor shaft when the load increases or decreases.

When setting up a circuit with a specific motor, resistance R12, choose a PIC depth at which self-oscillations of the rotation speed do not occur when the load changes.

Parts of electric motor rotation controllers

In these circuits, it is possible to use the following replacements of radio components: transistor KT817B - KT815, KT805; KT117A can be replaced with KT117B-G or 2N2646; Operational amplifier K140UD7 on K140UD6, KR544UD1, TL071, TL081; timer NE555 - S555, KR1006VI1; microcircuit TL074 - TL064, TL084, LM324.

When using a more powerful load, the KT817 key transistor can be replaced with a powerful field-effect transistor, for example, IRF3905 or similar.

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 a significant waste of electrical energy, but also to possible burnout of the tool. If the rotation speed is too high, 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. Nowadays, approximately 85% of motors used in electric tools, household or kitchen appliances are of the commutator 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 pass a direct current through it, the frame will begin to 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.

In addition, an important feature is that the rotation axis can be directly attached to a rotating tool 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?

There are various options for 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 identified during testing of its operation, is its poor suitability at very high current values. 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 at home, 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. To do this, you can use a metal plate that 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 of 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.

Not every modern drill or grinder is equipped with a factory speed regulator, and most often speed control is not provided at all. However, both angle grinders and drills are built on the basis of commutator motors, which allows each of their owners, even if they know how to handle a soldering iron, to make their own speed controller from available electronic components, either domestic or imported.

In this article we will look at the diagram and principle of operation of the simplest engine speed controller for a power tool, and the only condition is that the engine must be a commutator type - with characteristic lamellas on the rotor and brushes (which sometimes spark).

The above diagram contains a minimum of parts and is suitable for power tools up to 1.8 kW and above, for a drill or grinder. A similar circuit is used to regulate speed in automatic washing machines that have commutator high-speed motors, as well as in dimmers for incandescent lamps. Such circuits, in principle, will allow you to regulate the heating temperature of a soldering iron tip, an electric heater based on heating elements, etc.

The following electronic components will be required:

Constant resistor R1 - 6.8 kOhm, 5 W.

Variable resistor R2 - 2.2 kOhm, 2 W.

Constant resistor R3 - 51 Ohm, 0.125 W.

Film capacitor C1 - 2 µF 400 V.

Film capacitor C2 - 0.047 uF 400 volts.

Diodes VD1 and VD2 - for voltage up to 400 V, for current up to 1 A.

Thyristor VT1 - for the required current, for a reverse voltage of at least 400 volts.

The circuit is based on a thyristor. A thyristor is a semiconductor element with three terminals: anode, cathode, and control electrode. After a short pulse of positive polarity is applied to the control electrode of the thyristor, the thyristor turns into a diode and begins to conduct current until this current in its circuit is interrupted or changes direction.

After the current stops or when its direction changes, the thyristor will close and stop conducting current until the next short pulse is applied to the control electrode. Well, since the voltage in the household network is alternating sinusoidal, then each period of the network sinusoid the thyristor (as part of this circuit) will work strictly starting from the set moment (in the set phase), and the less the thyristor is open during each period, the lower the speed will be power tool, and the longer the thyristor is open, the higher the speed will be.

As you can see, the principle is simple. But when applied to a power tool with a commutator motor, the circuit works more cleverly, and we will talk about this later.

So, the network here includes in parallel: a measuring control circuit and a power circuit. The measuring circuit consists of constant and variable resistors R1 and R2, capacitor C1, and diode VD1. What is this chain for? This is a voltage divider. The voltage from the divider, and what is important, the back-EMF from the motor rotor, add up in antiphase, and form a pulse to open the thyristor. When the load is constant, then the open time of the thyristor is constant, therefore the speed is stabilized and constant.

As soon as the load on the tool, and therefore on the engine, increases, the value of the back-EMF decreases, since the speed decreases, which means the signal to the control electrode of the thyristor increases, and opening occurs with less delay, that is, the power supplied to the engine increases, increasing the dropped speed . This way the speed remains constant even under load.

As a result of the combined action of signals from the back-EMF and from the resistive divider, the load does not greatly affect the speed, but without a regulator this influence would be significant. Thus, using this circuit, stable speed control is achievable in each positive half-cycle of the network sinusoid. At medium and low rotation speeds this effect is more pronounced.

However, with increasing speed, that is, with increasing voltage removed from the variable resistor R2, the stability of maintaining a constant speed decreases.

In this case, it is better to provide a shunt button SA1 parallel to the thyristor. The function of diodes VD1 and VD2 is to ensure half-wave operation of the regulator, since the voltages from the divider and the rotor are compared only in the absence of current through the motor.

Capacitor C1 expands the control zone at low speeds, and capacitor C2 reduces sensitivity to interference from brush sparking. The thyristor needs to be highly sensitive so that a current of less than 100 μA can open it.