Adjusting the motor speed. Speed ​​controller for commutator motor: device and do-it-yourself manufacturing

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 AC
• 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 input circuit to the m/s phase, the internal units are synchronized with the VT139 triac.

The following figure shows the arrangement of elements on a printed circuit board. During installation and startup, attention should be paid to ensuring safe operating conditions - the regulator is powered by 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 to select the correct 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.

When starting the electric motor, the current consumption exceeds 7 times, which contributes to premature failure of the electrical and mechanical parts of the motor. To prevent this, you should use an electric motor speed controller. There are many factory-made models, but in order to make such a device yourself, you need to know the principle of operation of the electric motor and how to regulate rotor speed.

General information

AC electric motors have become widespread in many areas of human activity, namely asynchronous models. The main purpose of the engine as an electric machine is transformation of electrical energy into mechanical energy. Asynchronous in translation means non-simultaneous, since the rotor speed differs from the frequency of the alternating voltage (U) in the stator. There are two types of asynchronous motors based on the type of power supply:

1. Single-phase.
2. Three-phase.

Single-phase ones are used for household needs, and three-phase ones are used in production. Three-phase asynchronous motors (hereinafter referred to as TAM) use two types of rotors:

• closed;
• phase

Closed-circuit motors make up about 95% of all motors used and have significant power (from 250 W and above). The phase type is structurally different from the IM, but is used quite rarely compared to the first. The rotor is a cylindrical steel figure that is placed inside the stator, with a core pressed onto its surface.

Squirrel cage and wound rotors

Highly conductive copper (for high-power machines) or aluminum rods (for lower-power machines) soldered or poured into the surface of the core and short-circuited at the ends with two rings play the role of electromagnets with poles facing the stator. The winding rods do not have any insulation, since the voltage in such a winding is zero.

More commonly used for mid-power motor cores, aluminum has low density and high electrical conductivity.

To reduce higher harmonics of electromotive force (EMF) and eliminate magnetic field pulsation the rotor rods have a certain calculated angle of inclination relative to the axis of rotation. If a low-power electric motor is used, the grooves are closed structures that separate the rotor from the gap in order to increase the inductive component of the resistance.

The rotor in the form of a phase design or type is characterized by a winding, its ends are connected in a star type and attached to slip rings (on the shaft), along which graphite brushes slide. To eliminate eddy currents, the surface of the windings is covered with an oxide film. In addition, a resistor is added to the rotor winding circuit, which allows you to change the active resistance (R) of the rotor circuit to reduce the values ​​of inrush currents (Ip). Starting currents negatively affect the electrical and mechanical parts of the electric motor. Variable resistors used to regulate Ip:

1. Metal or stepped with manual switching.
2. Liquid (due to immersion to the depth of the electrodes).

Graphite brushes are subject to wear, and some models are equipped with a squirrel-cage design that lifts the brushes and closes the rings after the motor starts. IMs with a wound rotor are more flexible in terms of regulation of Ip.

Design features

An asynchronous motor does not have pronounced poles, unlike a DC electric motor. Number of poles determined by the number of coils in the windings fixed part (stator) and connection method. In an asynchronous machine with 4 coils, a magnetic flux passes through. The stator is made of special steel sheets (electrical steel), which reduce eddy currents to zero, at which significant heating of the windings occurs. It leads to a massive interturn short circuit.

The iron ore or rotor core is pressed directly onto the shaft. There is a minimum air gap between the rotor and stator. The rotor winding is made in the form of a “squirrel cage” and is made of copper or aluminum rods.

In electric motors with a power of up to 100 kW, aluminum, which has low density, is used to fill the grooves of the rotor core. But despite this device, engines of this type get hot. To solve this problem fans are used for forced cooling, which are mounted on the shaft. These engines are simple and reliable. However, motors consume a large current when starting, 7 times the rated current. Because of this, they have a low starting torque, since most of the electrical energy goes to heating the windings.

Electric motors, which have an increased starting torque, differ from ordinary asynchronous motors in the design of the rotor. The rotor is made in the form of a double “squirrel cage”. These models are similar to the phase types of rotor manufacturing. It consists of an inner and outer “squirrel cage”, and the outer one is the starting one and has a large active and small reactive R. The outer one has a slight active and high reactive R. As the rotation speed increases, I switches to the inner cage and operates in the form of a squirrel-cage rotor.

Principle of operation

When I flows through the stator winding, a magnetic flux (F) is created in each of them. These F are shifted by 120 degrees relative to each other. The resulting F is rotating, creating electromotive force (EMF) in aluminum or copper conductors. As a result of this, a starting magnetic moment of the electric motor is created, and the rotor begins to rotate. This process is also called slip (S) in some sources, showing the frequency difference n1 of the electromagnetic field of the starter, which becomes greater than the frequency obtained when rotor n2 rotates. It is calculated as a percentage and has the form: S = ((n1-n2)/n1) * 100%.

Scheme 1 - Thyristor speed control of a commutator motor without loss of power.

This circuit performs regulation by opening or closing thyristors (triacs) during a phase transition through the neutral. To correctly control a commutator motor, the following methods of modifying circuit 1 are used:

1. Installation of LRC protective circuits consisting of capacitors, resistors and chokes.
2. Adding capacitance at the input.
3. The use of thyristors or triacs, the current of which exceeds the rated value of the motor current in the range of 3..8 times.

This type of regulator has advantages and disadvantages. The first include low cost, low weight and dimensions. The second ones include the following:

• application for low power motors;
• there is noise and jerking of the motor;
• when using a circuit based on triacs, a constant U hits the motor.

This type of regulator is installed in fans, air conditioners, washing machines and electric drills. Performs its functions perfectly, despite its shortcomings.

Transistor type

Another name for a transistor-type regulator is an autotransformer or PWM regulator (scheme 2). It changes the value of U according to the principle of pulse width modulation (PWM) using an output stage that uses IGBT transistors.

Scheme 2 - Transistor PWM speed controller.

Switching of transistors occurs at a high frequency and thanks to this it is possible to change the width of the pulses. Consequently, the value of U will also change. The longer the pulse and the shorter the pause, the higher the value of U and vice versa. The positive aspects of using this variety are as follows:

1. Low weight of the device with small dimensions.
2. Quite low cost.
3. At low speeds there is no noise.
4. Control via low U values ​​(0..12 V).

The main disadvantage of the application is that the distance to the electric motor should be no more than 4 meters.

Frequency regulation

Scheme 3 - Frequency speed controller.

A specialized inverter has its advantages and disadvantages. The advantages are the following:

1. Blood pressure control without human intervention.
2. Stability.
3. Additional features.

It is possible to control the operation of the electric motor under certain conditions, as well as protection against overloads and short-circuit currents. In addition, it is possible to expand the functionality by connecting digital sensors, monitoring operating parameters and using a PID controller. The disadvantages include limitations in frequency control and a fairly high cost.

For three-phase IM, frequency control devices are also used (Scheme 4). The regulator has three phases at the output for connecting an electric motor.

Scheme 4 - Inverter for a three-phase motor.

This option also has its strengths and weaknesses. The first include the following: low cost, choice of power, wide range of frequency regulation, as well as all the advantages of single-phase frequency converters. Among all the negative aspects, the main ones can be identified: preliminary selection and heating during startup.

DIY making

If there is no opportunity or desire to purchase a factory-type regulator, then you can assemble it yourself. Although regulators of the "tda1085" type have proven themselves very well. To do this, you need to familiarize yourself with the theory in detail and start practicing. Triac circuits are very popular, in particular the speed controller of a 220V asynchronous motor (diagram 5). It's not difficult to make. It is assembled using a VT138 triac, which is well suited for these purposes.

Scheme 5 - A simple speed controller on a triac.

This regulator can also be used to adjust the speed of a 12-volt DC motor, as it is quite simple and universal. The speed is regulated by changing the parameters P1, which determines the phase of the incoming signal, which opens the transition of the triac.

The operating principle is simple. When the engine starts, it slows down, the inductance changes downward and contributes to an increase in U in the “R2->P1->C2” circuit. When C2 is discharged, the triac opens for some time.

There is another scheme. It works a little differently: by providing a reverse type of energy flow, which is optimally beneficial. The circuit includes a fairly powerful thyristor.

Scheme 6 - Design of a thyristor regulator.

The circuit consists of a control signal generator, an amplifier, a thyristor and a circuit section that functions as a rotor rotation stabilizer.

The most universal circuit is a regulator based on a triac and dinistor (scheme 7). It is able to smoothly reduce the shaft rotation speed, reverse the motor (change the direction of rotation) and reduce the starting current.

The principle of operation of the circuit:

1. C1 is charged until U breakdown of dinistor D1 through R2.
2. When D1 breaks, it opens the junction of triac D2, which is responsible for controlling the load.

​The load voltage is directly proportional to the frequency component when D2 opens, which depends on R2. The circuit is used in vacuum cleaners. It contains universal electronic control, as well as the ability to easily connect 380 V power. All parts should be placed on a printed circuit board made using laser-iron technology (LUT). You can find out more about this board manufacturing technology on the Internet.

Thus, when choosing an electric motor speed controller, you can buy a factory one or make it yourself. Making a homemade regulator is quite simple, since if you understand the principle of operation of the device, you can easily assemble it. In addition, you should follow safety rules when installing parts and when working with electricity.

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.

Each of us has some kind of electrical appliance at home that has been working in the house for more than one year. But over time, the power of the technology weakens and does not fulfill its intended purpose. This is when you should pay attention to the insides of the equipment. Mostly problems arise with the electric motor, which is responsible for the functionality of the equipment. Then you should turn your attention to a device that regulates engine speed without reducing its power.

Types of engines

A speed control with power maintenance is an invention that will breathe new life into an electrical appliance, and it will work like a newly purchased product. But it is worth remembering that engines come in different formats and each has its own maximum performance.

The engines have different characteristics. This means that this or that technique operates at different speeds of the shaft that triggers the mechanism. The motor may be:

1. single-phase,
2. two-phase,
3. three-phase.

Mostly three-phase electric motors are found in factories or large factories. At home, single-phase and two-phase are used. This electricity is enough to operate household appliances.

Power speed controller

Work principles

A 220 V electric motor speed controller without loss of power is used to maintain the initial set shaft speed. This is one of the basic principles of this device, which is called a frequency regulator.

With its help, the electrical device operates at the set engine speed and does not reduce it. The engine speed controller also affects the cooling and ventilation of the motor. With the help of power, the speed is set, which can be either raised or reduced.

Many people have asked the question of how to reduce the speed of a 220 V electric motor. But this procedure is quite simple. One has only to change the frequency of the supply voltage, which will significantly reduce the performance of the motor shaft. You can also change the power supply to the motor by activating its coils. Electrical control is closely related to the magnetic field and motor slip. For such actions, they mainly use an autotransformer and household regulators, which reduce the speed of this mechanism. But it is also worth remembering that engine power will decrease.

Shaft rotation

Engines are divided into:

1. asynchronous,
2. collector

The speed controller of an asynchronous electric motor depends on the current connection to the mechanism. The essence of the operation of an asynchronous motor depends on the magnetic coils through which the frame passes. It rotates on sliding contacts. And when, when turning, it turns 180 degrees, then through these contacts the connection will flow in the opposite direction. This way the rotation will remain the same. But with this action the desired effect will not be obtained. It will come into force after a couple of dozen frames of this type are added to the mechanism.

The commutator motor is used very often. Its operation is simple, since the passed current passes directly - because of this, the power of the electric motor is not lost, and the mechanism consumes less electricity.

The washing machine motor also needs power adjustment. For this purpose, special boards were made that cope with their job: the engine speed control board from a washing machine has multifunctional use, since its use reduces the voltage, but does not lose rotation power.

The circuit of this board has been verified. All you have to do is install diode bridges and select an optocoupler for the LED. In this case, you still need to put a triac on the radiator. Basically, engine adjustment starts at 1000 rpm.

If you are not satisfied with the power regulator and its functionality is lacking, you can make or improve the mechanism. To do this, you need to take into account the current strength, which should not exceed 70 A, and heat transfer during use. Therefore, an ammeter can be installed to adjust the circuit. The frequency will be small and will be determined by capacitor C2.

Next, you should configure the regulator and its frequency. When outputting, this pulse will go out through a push-pull amplifier using transistors. You can also make 2 resistors that will serve as an output for the computer's cooling system. To prevent the circuit from burning out, a special blocker is required, which will serve as double the current value. So this mechanism will work for a long time and in the required volume. Power regulating devices will provide your electrical appliances with many years of service without special costs.

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.