Schemes of speed controllers for low-voltage brushed motors. Types and design of speed controllers for commutator motors. Overview of typical circuits

Any modern power tool or household appliance uses a commutator motor. This is due to their versatility, i.e. the ability to operate on both alternating and direct voltage. Another advantage is the efficient starting torque.

However, the high speed of the commutator motor does not suit all users. For a smooth start and the ability to change the speed of rotation, a regulator was invented, which is quite possible to make with your own hands.

Operating principle and types of commutator motors

Each electric motor consists of a commutator, stator, rotor and brushes. The principle of its operation is quite simple:

In addition to the standard device, there are also:

Regulator device

There are many schemes of such devices in the world. Nevertheless, they can all be divided into 2 groups: standard and modified products.

Standard device

Typical products are distinguished by ease of manufacture of the idynistor and good reliability when changing engine speed. As a rule, such models are based on thyristor regulators. The operating principle of such schemes is quite simple:

Thus, the speed of the commutator motor is adjusted. In most cases, a similar scheme is used in foreign household vacuum cleaners. However, you should know that such a speed controller does not have feedback. Therefore, when the load changes, you will have to adjust the speed of the electric motor.

Changed schemes

Of course, the standard device suits many fans of speed controllers to “dig” into the electronics. However, without progress and improvement of products, we would still be living in the Stone Age. Therefore, more interesting schemes are constantly being invented, which many manufacturers are happy to use.

The most commonly used are rheostat and integral regulators. As the name implies, the first option is based on a rheostat circuit. In the second case, an integral timer is used.

Rheostatic ones are effective in changing the number of revolutions of the commutator motor. High efficiency is due to power transistors, which take part of the voltage. Thus, the current flow is reduced and the motor works with less effort.

Video: speed control device with power maintenance

The main disadvantage of this scheme is the large amount of heat generated. Therefore, for smooth operation, the regulator must be constantly cooled. Moreover, the cooling of the device must be intensive.

A different approach is implemented in an integral regulator, where an integral timer is responsible for the load. As a rule, transistors of almost any type are used in such circuits. This is due to the fact that it contains a microcircuit with large output current values.

If the load is less than 0.1 ampere, then all the voltage goes directly to the microcircuit, bypassing the transistors. However, for the regulator to operate effectively, it is necessary that there be a voltage of 12V at the gate. Therefore, the electrical circuit and the supply voltage itself must correspond to this range.

Overview of typical circuits

You can regulate the rotation of the shaft of a low-power electric motor by connecting a power resistor in series with no. However, this option has very low efficiency and the inability to smoothly change speed. To avoid such a nuisance, you should consider several regulator circuits that are used most often.

As you know, PWM has a constant pulse amplitude. In addition, the amplitude is identical to the supply voltage. Consequently, the electric motor will not stop even when running at low speeds.

The second option is similar to the first. The only difference is that an operational amplifier is used as the master oscillator. This component has a frequency of 500 Hz and produces triangular-shaped pulses. Adjustment is also carried out using a variable resistor.

How to make it yourself

If you don’t want to spend money on purchasing a ready-made device, you can make it yourself. This way, you can not only save money, but also gain useful experience. So, to make a thyristor regulator you will need:

• soldering iron (to check functionality);
• wires;
• thyristor, capacitors and resistors;
• scheme.

As can be seen from the diagram, the regulator controls only 1 half-cycle. However, for testing performance on a regular soldering iron, this will be quite enough.

If you don’t have enough knowledge to decipher the diagram, you can familiarize yourself with the text version:

The use of regulators allows for more economical use of electric motors. In certain situations, such a device can be made independently. However, for more serious purposes (for example, monitoring heating equipment), it is better to purchase a ready-made model. Fortunately, there is a wide selection of such products on the market, and the price is quite affordable.

The motor from a washing machine, which is great for homemade items, has too high speeds and a short lifespan at maximum speeds. Therefore, I use a simple homemade speed controller (without loss of power). The scheme was tested and showed excellent results. The speed is adjustable from approximately 600 to max.

The potentiometer is electrically isolated from the network, which increases the safety of using the regulator.

The triac must be placed on the radiator.

Almost any optocoupler (2 pcs), but EL814 has 2 counter LEDs inside, and is suitable for this circuit.

A high-voltage transistor can be installed, for example, IRF740 (from a computer's power supply), but it would be a shame to install such a powerful transistor in a low-current circuit. Transistors 1N60, 13003, KT940 work well.

Instead of the KTs407 bridge, a 1N4007 bridge, or any one with >300V, and a current of >100mA, is quite suitable.

Signet in .lay5 format. The signet is drawn “View from the M2 side (soldering)”, so When outputting to a printer, it must be mirrored. Color M2 = black, background = white, do not print other colors. The outline of the board (for cutting) is made on the M2 side, and will indicate the boundaries of the board after etching. It should be removed before sealing parts. A drawing of parts from the mounting side has been added to the signet for transfer to the signet. It then takes on a beautiful and finished look.

Adjustment from 600 rpm is suitable for most homemade products, but for special cases a circuit with a germanium transistor is proposed. The minimum speed was reduced to 200.

The minimum speed was 200 rpm (170-210, the electronic tachometer does not measure well at low speeds), the T3 transistor was installed GT309, it is direct conduction, and there are many of them. If you put MP39, 40, 41, P13, 14, 15, then the speed should decrease further, but I no longer see the need. The main thing is that such transistors are like dirt, unlike MP37 (see forum).

Soft start works great, True, the motor shaft is empty, but due to the load on the shaft during start-up, I will select R5 if necessary.

R5 = 0-3k3 depending on the load;; R6 = 18 Ohm - 51 Ohm - depending on the triac, I don’t have this resistor now;; R4 = 3k - 10k - T3 protection;; RP1 = 2k-10k - speed controller, connected to the network, protection from the operator's mains voltage is required!!!. There are potentiometers with a plastic axis, it is advisable to use them!!!This is a big drawback of this scheme, and if there is no great need for low speeds, I advise you to use V17 (from 600 rpm).

C2 = soft start, = delay time for turning on the motor;; R5 = charge C2, = charge curve slope, = motor acceleration time;; R7 - C2 discharge time for the next soft start cycle (at 51k this is approximately 2-3 seconds)

List of radioelements

Designation	Type	Denomination	Quantity	Note	Shop	My notepad
T1	Triac	BT139-600	1			To notepad
T2	Dinistor		1			To notepad
VD	Diode bridge	KTs407A	1			To notepad
VD4	Rectifier diode	1N4148	1			To notepad
C2	Capacitor	220 uF x 4 V	1			To notepad
C1	Capacitor	100 nF x 160 V	1			To notepad
R1	Resistor	3.3 kOhm 0.5W	1			To notepad
R2	Resistor	330 Ohm 0.5W	1			To notepad
R3	Resistor	470 kOhm 0.125W	1			To notepad
R4	Resistor	200 Ohm 0.125W	1			To notepad
R5	Resistor	200 Ohm 0.125W	1			To notepad
V1	Optocoupler	PC817	2			To notepad
T3	Bipolar transistor	GT309G	1			To notepad
C2a	Capacitor	47 uF x 4 V	1

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.