Schemes for adjusting the speed of an AC motor

Types of adjustment

There are quite a few options for adjusting the speed. Here are the main ones:

• Power supply with adjustable output voltage.
• Factory adjustment devices that initially come with the electric motor.
• Push-button regulators and standard regulators that simply limit the voltage.

These types of adjustments are bad because as the voltage decreases or increases, the power also drops. In some power tools this is acceptable, but, as practice shows, in most cases this is unacceptable due to a strong drop in power and, accordingly, efficiency.

The most acceptable option would be a regulator based on a triac or thyristor. Not only does such a regulator not reduce power when the voltage decreases, it also allows for smoother starting and speed control. In addition, such a scheme can be made with your own hands. Below is a picture of the speed control with power maintenance. The circuit is assembled on the basis of a BTA 41,800 V triac.

All ratings of electrical elements are indicated in the diagram. This is the circuit after assembly, it works quite stably and provides smooth adjustment of the brushed motor. When the output voltage decreases, the power does not decrease, which is a significant plus.

If desired, you can assemble the speed controller of a 220 V brushed motor with your own hands. This circuit is assembled on the basis of a VTA26-600 triac, which must first be installed on a radiator, since this element gets quite hot under load.

The diagram looks like this.

It can successfully cope with the adjustment of power tools such as a drill, grinder, circular saw, and jigsaw. If desired, you can use the circuit as a power regulator for heating elements, heaters, and as a dimmer. The disadvantages include the impossibility of adjusting the power of devices powered by direct current.

https://youtube.com/watch?v=vVeR4jVfTIg

Generalized controller circuit

An example of a controller that implements the principle of controlling a motor without power loss is a thyristor converter. These are proportional-integral circuits with feedback, which provide strict control of characteristics, ranging from acceleration-braking to reverse. The most effective is pulse-phase control: the repetition rate of the unlocking pulses is synchronized with the network frequency. This allows you to maintain torque without increasing losses in the reactive component. The generalized diagram can be represented in several blocks:

• power controlled rectifier;
• rectifier control unit or pulse-phase control circuit;
• tachogenerator feedback;
• current control unit in the motor windings.

Before delving into a more precise device and principle of regulation, it is necessary to decide on the type of commutator motor. The control scheme for its performance characteristics will depend on this.

Types of devices

Triac device

The triac device is used to control lighting, power of heating elements, and rotation speed.

The controller circuit based on a triac contains a minimum of parts shown in the figure, where C1 is a capacitor, R1 is the first resistor, R2 is the second resistor.

Using a converter, power is regulated by changing the time of an open triac. If it is closed, the capacitor is charged by the load and resistors. One resistor controls the amount of current, and the second regulates the charging rate.

When the capacitor reaches the maximum voltage threshold of 12V or 24V, the switch is activated. The triac goes into the open state. When the mains voltage passes through zero, the triac is locked, and then the capacitor gives a negative charge.

Measurements

It is clear that the number of revolutions needs to be determined somehow. Tachometers are used for this. They show the rotation number at the moment. You can’t simply measure speed with a regular multimeter, except in a car.

As you can see, on electric machines you can change various parameters, adjusting them to the needs of production and household use.

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Pointed-toe cowboy bootsThe principle of operation of a homemade lock is as follows. In one half there is a permanent magnet. and in the other there is a metal plate. One of them is attached to the door. The second, with the metal plate removed, is equipped with a KEM-1 reed switch and attached to the door frame. If the door is in the closed position, the two parts of the lock are pressed, the magnet acts on the reed switch, closing its contacts. If the door opens, the magnet goes away and the reed switch contacts open.

The battery, the computer system unit, even the power supply for a laptop are all best friends. I’m already silent about such good hot water bottles as my husband and I.

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For the base of such a structure, you can use thick plywood, and for its upper part - polycarbonate. Finding solar panels online today is also not a problem.

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To make a feeder with your own hands we will need:

Timber calculation. The boards, called staves, have biconvex sides to give the cooperage product a convexity. To make them like this, you need to take the lower part of a tree trunk and split it, similar to chopping wood. If you cut it carefully, the natural integrity of the fibers will be disrupted, which is bad for such a product. You shouldn’t start figure sawing right away - the logs need to be dried for 2 months. Moreover, dry it not under the scorching sun, but in a dark, cool room.

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The fact that most New Year's costumes for preschool children are easily sewn on the basis of overalls can significantly narrow and facilitate creative search. If you learn how to sew a jumpsuit - the basis for a New Year's costume and come up with (draw from) and make decorative elements for it with your own hands, then you can make amazing and quite interesting models of New Year's outfits for children. The main thing is to think through everything in advance to the smallest detail, arm yourself with knowledge on the topic - so that the result of the work will pleasantly surprise and delight everyone.

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With the ever-increasing growth of automation in the domestic sector, there is a need for modern systems and devices for controlling electric motors.

Control and frequency conversion in small-power single-phase asynchronous motors, launched using capacitors, allows you to save energy and activates the energy saving mode at a new, progressive level.

Making homemade relays

Making a homemade speed controller for a 12 V electric motor will not be difficult. For this work you will need the following:

• Wirewound resistors.
• Switch for several positions.
• Control unit and relay.

The use of wirewound resistors allows you to change the supply voltage and, accordingly, the engine speed. Such a regulator provides stepwise acceleration of the engine, has a simple design and can be made even by novice radio amateurs. Such simple homemade step regulators can be used with asynchronous and contact motors.

Operating principle of a homemade converter:

1. Power from the network is sent to the capacitor.
2. The used capacitor is fully charged.
3. The load is transferred to the resistor and the bottom cable.
4. The thyristor electrode connected to the positive terminal on the capacitor receives the load.
5. A voltage charge is transmitted.
6. The discovery of the second semiconductor occurs.
7. The thyristor passes the load received from the capacitor.
8. The capacitor is completely discharged, after which the half-cycle is repeated.

In the past, the most popular were mechanical regulators based on a variator or gear drive. However, they were not very reliable and often failed.

Homemade electronic regulators have proven themselves to be the best. They use the principle of changing step or smooth voltage, are durable, reliable, have compact dimensions and provide the ability to fine-tune the operation of the drive.

The additional use of triacs and similar devices in electronic regulator circuits allows for a smooth change in voltage power; accordingly, the electric motor will correctly gain speed, gradually reaching its maximum power.

Voltage regulation

Speed ​​control in this way is associated with a change in the so-called engine slip - the difference between the rotation speed of the magnetic field created by the stationary engine stator and its moving rotor:

n1—magnetic field rotation speed

n2—rotor rotation speed

In this case, sliding energy is necessarily released - which causes the motor windings to heat up more.

This method has a small control range, approximately 2:1, and can also only be carried out downwards - that is, by reducing the supply voltage.

When regulating speed in this way, it is necessary to install oversized motors.

But despite this, this method is used quite often for low-power motors with a fan load.

In practice, various regulator circuits are used for this.

Autotransformer voltage regulation

An autotransformer is an ordinary transformer, but with one winding and taps from some of the turns. In this case, there is no galvanic isolation from the network, but in this case it is not needed, so savings are achieved due to the absence of a secondary winding.

The diagram shows autotransformer T1, switch SW1, which receives taps with different voltages, and motor M1.

The adjustment is done in steps; usually no more than 5 steps of regulation are used.

Advantages of this scheme:

• undistorted output voltage waveform (pure sine wave)
• good overload capacity of the transformer

Flaws:

• large mass and dimensions of the transformer (depending on the power of the load motor)
• all the disadvantages inherent in voltage regulation

Thyristor engine speed controller

This circuit uses keys - two thyristors connected back-to-back (the voltage is alternating, so each thyristor passes its own half-wave of voltage) or a triac.

The control circuit regulates the moment of opening and closing of the thyristors relative to the phase transition through zero; accordingly, a piece is “cut off” at the beginning or, less often, at the end of the voltage wave.

This changes the rms voltage value.

This circuit is quite widely used to regulate active loads - incandescent lamps and all kinds of heating devices (so-called dimmers).

Another method of regulation is to skip half-cycles of the voltage wave, but at a network frequency of 50 Hz this will be noticeable for the motor - noise and jerking during operation.

To control motors, regulators are modified due to the characteristics of the inductive load:

• install protective LRC circuits to protect the power switch (capacitors, resistors, chokes)
• add a capacitor at the output to adjust the voltage waveform
• limit the minimum voltage regulation power - for guaranteed engine start
• use thyristors with a current several times higher than the electric motor current

Advantages of thyristor regulators:

Flaws:

• can be used for low power engines
• During operation, noise, crackling, and jerking of the engine may occur.
• when using triacs, a constant voltage is applied to the motor
• all the disadvantages of voltage regulation

It is worth noting that in most modern mid- and high-level air conditioners, the fan speed is adjusted in this way.

Transistor voltage regulator

As the manufacturer himself calls it, an electronic autotransformer or PWM regulator.

The voltage is changed using the PWM (pulse width modulation) principle, and transistors are used in the output stage - field-effect or bipolar with insulated gate (IGBT).

The output transistors are switched at a high frequency (about 50 kHz); if you change the width of the pulses and pauses between them, the resulting voltage at the load will also change. The shorter the pulse and the longer the pause between them, the lower the resulting voltage and power input.

For a motor, at a frequency of several tens of kHz, a change in the pulse width is equivalent to a change in voltage.

The output stage is the same as that of a frequency converter, only for one phase there is a diode rectifier and two transistors instead of six, and the control circuit changes the output voltage.

Advantages of an electronic autotransformer:

• Small dimensions and weight of the device
• Low cost
• Clean, undistorted current output waveform
• No hum at low speeds
• 0-10 Volt signal control

Weak sides:

• The distance from the device to the engine is no more than 5 meters (this disadvantage is eliminated when using a remote controller)
• All the disadvantages of voltage regulation

Power speed regulator

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:

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 transmitted 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.

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.

Using Pulse Width Modulation

To control and adjust the speed of rotation of an asynchronous type electric motor, you can use a pulse regulator-voltage stabilizer (inverter). It will act as a power source. It is based on the use of a TL494 pulse PWM regulator. The supply voltage of the electric motor, coming out after the PWM controller, will change in accordance with the change in rotation speed. Using this method, a greater economic effect is achieved, the device is quite simple and at the same time increases the efficiency of regulation.

The figure above shows a diagram of using a PWM controller for a three-phase asynchronous motor connected through a capacitor to a single-phase network.

This method, despite its effectiveness, has two significant drawbacks:

• impossibility of reverse motor control without the use of additional switching devices;
• frequency converters used in the regulator are high cost and are produced by a limited number of manufacturers.

Operating principle of a single-phase asynchronous machine

When an asynchronous machine is supplied with single-phase power, instead of a rotating magnetic field, a pulsating one appears in it, which can be decomposed into two magnetic fields, which will rotate in different directions with the same frequency and amplitude. When the electric motor rotor is stopped, these fields will create moments of the same magnitude, but of different signs. As a result, the resulting starting torque will be zero, which will not allow the engine to start. In its properties, a single-phase electric motor is similar to a three-phase one, which operates with a strong distortion of voltage symmetry:

Figure a) shows a diagram of an asynchronous single-phase machine, and b) a vector diagram

Types of engines and operating principles

Motors are divided into three types: commutator, asynchronous and brushless. Most power tools use the first type. This electric motor has a fairly compact size. Its power is significantly higher than that of asynchronous, and the price is quite low. As for asynchronous ones, this type is mainly used in the metalworking industry, and they are also widespread in coal mines. Quite rarely they can be found in everyday life.

The brushless electric motor is used where high speeds, precise positioning and small dimensions are needed. For example, in various medical equipment, aircraft modeling. The principle of operation is quite simple. If a rectangular frame, which has an axis of rotation, is placed between the pluses of a permanent magnet, then it will begin to rotate. The direction depends on the direction of the current in the frame. This type contains an armature and a stator. The armature rotates, but the stator stands still. As a rule, there is not one frame at anchor, but 4.5 or more.

An asynchronous motor works on a different principle. Thanks to the effect of an alternating magnetic field in the stator coils, it is driven into rotation. If you delve deeper into the course of physics, you can remember that a kind of magnetic field is created around the conductor through which the current passes, causing the rotor to rotate.

The principle of operation of the brushless type is based on turning on the windings so that the magnetic fields of the stator and rotor are orthogonal to each other, and the torque is regulated by a special driver.

The figure clearly shows that in order to move the rotor it is necessary to perform the necessary commutation, but it is not possible to regulate the speed. However, the brushless motor can rev up very quickly.

Main types of single-phase electric drives

As mentioned, a single-phase motor cannot develop starting torque, which makes it impossible to start it independently. To do this, they came up with several ways to compensate for a magnetic field that is opposite in sign to the main one.

Motors with starting winding

In this starting method, in addition to the main winding P, which has a phase zone of 120 0, a starting winding P, which has a phase zone of 60 0, is also wound on the stator. Also, the starting winding shifts relative to the working winding by 90 0 electrical. In order to create a phase shift between the winding currents Ip and Ip, an element leading to a phase shift ψ (phase-shifting resistance Zp) is connected in series to the starting winding:

Where: a) connection diagram of the machine, b) vector diagrams when using different resistances.

The best conditions for starting are to include a capacitor in the starting winding. But since the capacitor capacity is quite large, its cost and dimensions also increase accordingly. It is often used to obtain increased starting torque. Inductive starting has the worst performance and is not currently used. Quite often, starting with the help of active resistance can be used, while the starting winding is made with increased active resistance. After the electric motor starts, the starting winding is turned off. The connection diagrams and their starting characteristics are shown below:

Where: a, b) motors with a starting winding, c, d) capacitor motors

Capacitor motor

This type of electric motor has two working windings, one of which is connected to the working capacitance Cp. These windings are shifted relative to each other by 90 0 electrical and have phase zones also 90 0. In this case, the powers of both windings are equal, but their currents and voltages are different, and the number of turns is also different. Sometimes the size of the working capacitor is not enough to generate the required starting torque, so a starting one can be hung in parallel with it, as shown in the figure above. The diagram is shown below:

Where: a) circuit of a capacitor electric motor, b) its vector diagram

In this type of single-phase machines, the power factor cosφ is even higher than that of three-phase machines. This is due to the presence of a capacitor. The efficiency of such an electric motor is higher than that of a single-phase electric motor with a starting winding.

What is an asynchronous motor?

AC electric motors have found quite wide application in various spheres of our life, in hoisting, processing, and measuring equipment. They are used to convert electrical energy that comes from the network into mechanical energy of a rotating shaft. Most often, asynchronous AC converters are used. In them, the rotation speed of the rotor and stator is different. A structural air gap is provided between these active elements.

Both the stator and the rotor have a rigid core made of electrical steel (composited type, made of plates), acting as a magnetic circuit, as well as a winding that fits into the structural grooves of the core. It is the way in which the rotor winding is organized or laid out that is the key criterion for classifying these machines.

Squirrel-cage motors (SCR)

Here, a winding is used in the form of aluminum, copper or brass rods, which are inserted into the grooves of the core and closed on both sides by disks (rings). The type of connection of these elements depends on the engine power: for small values, the method of joint casting of disks and rods is used, and for large values, separate production is used, followed by welding to each other. The stator winding is connected using delta or star circuits.

Wound rotor motors

The three-phase rotor winding is connected to the network via slip rings on the main shaft and brushes. The “star” scheme is taken as the basis. The figure below shows a typical design of such an engine.

Changing the speed of an IM with a squirrel-cage rotor

There are several ways:

1. Rotation control by changing the electromagnetic field of the stator: frequency regulation and changing the number of pole pairs.

1. Changing the slip of the electric motor by decreasing or increasing the voltage (can be used for IMs with a wound rotor).

Frequency regulation

In this case, the adjustment is made using a frequency conversion device connected to the engine. For this purpose, powerful thyristor converters are used. The process of frequency regulation can be considered using the example of the EMF formula of a transformer:

This expression means that in order to maintain a constant magnetic flux, which means maintaining the overload capacity of the electric motor, the supply voltage level should be adjusted simultaneously with frequency conversion. If the expression calculated by the formula is saved:

then this means that the critical moment has not been changed. And the mechanical characteristics correspond to the figure below; if you do not understand what these characteristics mean, then in this case the adjustment occurs without loss of power and torque.

The advantages of this method are:

• smooth regulation;
• changing the rotor speed up and down;
• rigid mechanical characteristics;
• efficiency.

There is only one drawback - the need for a frequency converter, i.e. increase in the cost of the mechanism. By the way, on the modern market there are models with single-phase and three-phase input, the cost of which with a power of 2-3 kW is in the range of 100-150 dollars, which is not too expensive for full adjustment of the drive of machine tools in a private workshop.

Switching the number of pole pairs

This method is used for multi-speed motors with complex windings that allow you to change the number of pairs of its poles. The most widely used are two-speed, three-speed and four-speed IMs. The adjustment principle is easiest to consider on the basis of a two-speed IM. In such a machine, the winding of each phase consists of two half-windings. The rotation speed changes when connecting them in series or parallel.

In a four-speed electric motor, the winding is made in the form of two parts independent from each other. When the number of pole pairs of the first winding changes, the speed of the electric motor changes from 3000 to 1500 rpm. Using the second winding, rotation is adjusted at 1000 and 500 rpm.

When the number of pole pairs changes, the critical moment also changes. To keep it unchanged, it is necessary to simultaneously regulate the supply voltage while changing the number of pole pairs, for example, by switching the star-delta circuit and their variations.

Advantages of this method:

• rigid mechanical characteristics of the engine;
• high efficiency.

• step adjustment;
• large weight and overall dimensions;
• high cost of the electric motor.

Engine device

To make a speed controller with your own hands, you will first need to understand the details. The high demand for self-assembly lies in its versatility. By making a simple speed controller with your own hands, you can use it in various situations. So, first, let's understand a little about the structure of a simple commutator motor.

It consists of the following components:

1. Collector.
2. Brushes.
3. Rotor.
4. Stator.

Operating principle of a commutator motor:

• The source of electricity is a standard 220 V socket. Power goes to the main winding.
• After electricity is supplied from a source to the stator winding, a magnetic field is created in it.
• The magnetic field drives the rotor.
• Through graphite brushes, the voltage is transmitted to the commutator, whose task is to constantly switch the direction of the current so that the rotor ultimately rotates in one direction.

Design Features

The microcircuit is equipped with everything necessary for high-quality engine control in various speed modes, from braking to acceleration and rotation at maximum speed. Therefore, its use greatly simplifies the design, while simultaneously making the entire drive universal, since you can select any speed with a constant torque on the shaft and use it not only as a drive for a conveyor belt or drilling machine, but also for moving a table.

The characteristics of the microcircuit can be found on the official website. We will indicate the main features that will be required to construct the converter. These include: an integrated frequency-to-voltage conversion circuit, an acceleration generator, a soft starter, a Tacho signal processing unit, a current limiting module, etc. As you can see, the circuit is equipped with a number of protections that will ensure stable operation of the regulator in different modes.

The figure below shows a typical circuit diagram for connecting a microcircuit.

The scheme is simple, so it is quite reproducible with your own hands. There are some features that include limit values ​​and speed control method:

• The maximum current in the motor windings should not exceed 10 A (subject to the configuration shown in the diagram). If you use a triac with a large forward current, the power can be higher. Please note that you will need to change the resistance in the feedback circuit downward, as well as the inductance of the shunt.
• The maximum rotation speed is 3200 rpm. This characteristic depends on the type of engine. The circuit can control motors up to 16 thousand rpm.
• Acceleration time to maximum speed reaches 1 second.
• Normal acceleration is achieved in 10 seconds from 800 to 1300 rpm.
• The engine uses an 8-pole tachogenerator with a maximum output voltage of 30 V at 6000 rpm. That is, it should produce 8 mV per 1 rpm. At 15,000 rpm it should show 12 V.
• To control the motor, a 15A triac with a maximum voltage of 600 V is used.

If you need to organize a motor reverse, then for this you will have to supplement the circuit with a starter that will switch the direction of the excitation winding. You will also need a zero speed control circuit to give permission for reverse. Not shown in the picture.

Frequency regulation

Just recently (10 years ago), there were a limited number of frequency controllers for motor speeds on the market, and they were quite expensive. The reason was that there were no cheap high-voltage power transistors and modules.

But developments in the field of solid-state electronics have made it possible to bring power IGBT modules to the market. As a consequence, there is a massive appearance on the market of inverter air conditioners, welding inverters, and frequency converters.

At the moment, frequency conversion is the main way to regulate the power, performance, speed of all devices and mechanisms driven by an electric motor.

However, frequency converters are designed to control three-phase electric motors.

Single-phase motors can be controlled by:

• specialized single-phase inverters
• three-phase inverters with the exception of the capacitor

Converters for single-phase motors

Currently, only one manufacturer announces serial production of a specialized inverter for capacitor motors - INVERTEK DRIVES.

Optidrive E2 model

For stable engine starting and operation, special algorithms are used.

In this case, frequency adjustment is possible upward, but in a limited frequency range, this is prevented by a capacitor installed in the phase-shifting winding circuit, since its resistance directly depends on the frequency of the current:

f - current frequency

C - capacitance of the capacitor

The output stage uses a bridge circuit with four output IGBT transistors:

Optidrive E2 allows you to control the motor without removing the capacitor from the circuit, that is, without changing the motor design - in some models this is quite difficult to do.

Advantages of a specialized frequency converter:

• intelligent motor control
• Stably stable engine operation
• the enormous capabilities of modern inverters: the ability to control the operation of the motor to maintain certain characteristics (water pressure, air flow, speed under changing load)
• numerous protections (motor and device itself)
• sensor inputs (digital and analogue)
• various outputs
• communication interface (for control, monitoring)
• preset speeds
• PID controller

Disadvantages of using a single-phase inverter:

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 - 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.

Smooth engine operation, without jerks or power surges, is the key to its durability. To control these indicators, an electric motor speed controller is used for 220V, 12V and 24V; all of these frequencies can be made with your own hands or you can buy a ready-made unit.