Control principle
When the speed of rotation of the motor shaft is set by the resistor in the output circuit 5, a sequence of pulses is formed at the output to unlock the triac by a certain angle value. The speed is monitored by tachogenerators, which occurs digitally. The driver converts the received pulses into an analog voltage, due to which the shaft speed is stabilized at a single value, regardless of the load. If the voltage from the tachogenerator changes, the internal regulator will increase the level of the triac control output signal, which will lead to an increase in speed.
The microcircuit can control two linear accelerations to achieve the dynamics required from the motor. One of them is set on Ramp 6 pin of the circuit. This regulator is used by the manufacturers of washing machines themselves, therefore it has all the advantages in order to be used for domestic purposes. This is ensured by the presence of the following blocks:
- Voltage regulator to ensure the normal operation of the control circuit. It is implemented according to conclusions 9, 10.
- Rotation speed control circuit. Implemented by MC pins 4, 11, 12 If necessary, the controller can be transferred to an analog sensor, then pins 8 and 12 are combined.
- Block of starting pulses. It is implemented on pins 1, 2, 13, 14, 15 Performs adjustment of the duration of control pulses, delay, shaping them from a constant voltage and calibration.
- Sawtooth voltage generating device. Pins 5, 6 and 7. It is used to control the speed according to the setpoint.
- Control amplifier circuit. Conclusion 16. Allows you to adjust the difference between the set and actual speed.
- Current limiting device at pin 3. When the voltage rises on it, the triac firing angle decreases.
The use of such a scheme provides full control of the collector motor in any mode. Thanks to the forced control of acceleration, it is possible to achieve the required acceleration speed to the specified speed. Such a regulator can be used for all modern engines from washing machines used for other purposes.
Generalized regulator circuit
An example of a regulator that implements the principle of controlling a motor without power loss is a thyristor converter. These are proportional integrated circuits with feedback, which provide tight regulation of characteristics, starting from acceleration-deceleration and ending with reverse. The most effective is the pulse-phase control: the unlocking pulse repetition rate is synchronized with the mains frequency. This allows the torque to be maintained without increasing losses in the reactive component. The generalized scheme can be represented by Several blocks:
- Power controlled rectifier;
- Rectifier control unit or pulse-phase control circuit;
- Feedback on tachogenerators;
- Motor winding current control unit.
Before delving into a more precise device and principle of regulation, it is necessary to determine the type of the collector motor. The control scheme for its performance will depend on this.
Adjustment
Now let’s talk about how you can regulate the speed of the collector motors. Due to the fact that the speed of rotation of the motor simply depends on the value of the supplied voltage, then any means of adjustment that are capable of performing this function are quite suitable for this.
Let’s list a few of these options for example:
- Laboratory autotransformer (LATR).
- Factory adjustment boards used in household appliances (you can use in particular those that are used in a mixer or vacuum cleaner).
- Buttons used in the construction of the power tool.
- Smooth-acting household dimmers.
However, all of the above methods have a very important flaw. Together with a decrease in revolutions, the engine power also decreases. In some cases, it can be stopped even with just a hand. In some cases, this may be acceptable, but for the most part, it is a serious obstacle.
A good option is to perform speed control by using a tachogenerator. It is usually installed at the factory. In case of deviations in the speed of rotation of the motor, the already corrected power supply corresponding to the required speed of rotation is transmitted to the motor through the triacs. If the motor rotation control is built into this circuit, then power loss will not occur here.
How does it look constructive? The most common rheostat regulation of rotation, and made on the basis of the use of semiconductors.
In the first case, we are talking about variable resistance with mechanical adjustment. It is connected in series to the collector motor. The disadvantage is the additional heat generation and additional waste of battery life. With this method of adjustment, there is a loss of motor rotation power. It 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 supplying certain pulses. The circuit can change the duration of such pulses, which in turn, changes the rotation speed without losing power.
Electric motor speed controller without power loss
The board for adjusting the revolutions of the collector electric motors on the TDA1085 microcircuit allows you to control the motors without losing power. A prerequisite for this is the presence of a tachometer (tachogenerator) on the electric motor, which allows the motor to provide feedback with the control board, namely the microcircuit. In simpler terms, so that it would be clear to everyone, something like the following happens. The motor rotates with a certain number of revolutions, and the installed tachometer on the shaft of the electric motor fixes these readings. If you start to load the engine, the shaft speed will naturally begin to drop, which will also fix the tachometer. Now let’s look further. The signal from this tachometer goes to the microcircuit, it sees this and gives a command to the power elements to add voltage to the electric motor. Thus, when you pressed on the shaft (giving a load), the board automatically added voltage and the power on this shaft increased. Conversely, let go of the motor shaft (remove the load from it), she saw this and reduced the voltage. Thus, the speed remains NOT low, and the moment of force (torque) remains constant. And most importantly, you can adjust the rotor speed in a wide range, which is very convenient in the use and design of various devices. Therefore, this product is called “Board for adjusting the speed of collector motors without power loss”.
But we saw one peculiarity that this board is applicable only for collector motors (with electric brushes). Of course, such motors are much less common in everyday life than asynchronous ones. But they are widely used in automatic washing machines. This is why this circuit was made. Especially for the electric motor from the washing machine automatic machine. Their power is quite decent, here are 200 to 800 watts. Which allows them to be widely used in everyday life.
This product has already found wide application in the household of people and has widely covered people engaged in various hobbies and professional activities.
Answering the question. Where can you apply the motor from the washing machine? Some list was formed. Homemade wood lathe; Grinder; Electric drive for concrete mixer; sharpener; Electric drive for honey extractor; straw chopper; Homemade Pottery Wheel; Electric lawn mower; Wood splitter and many other things where mechanical rotation of any mechanisms or objects is necessary. And in all THESE cases, we are helped by this board “Adjusting the speed of electric motors with maintaining power on the TDA1085”.
Work principles
The 220 V motor speed controller without power loss 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 the help of it, the electrical appliance operates at the set engine speed and DOES NOT reduce it. Also, the motor speed controller affects the cooling and ventilation of the motor. With the help of power, the speed is set, which can be either raised or lowered.
The question of how to reduce the speed of a 220 V electric motor was asked by many people. But this procedure is pretty 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 of the motor by using its coils. Electricity control is closely related to the magnetic field and motor slip. For such actions, they mainly use an autotransformer, household regulators, which reduce the speed of this mechanism. But it is also worth remembering that engine power will decrease.
Types of engines
Engines are different in characteristics. This means that one or another technique works at different frequencies of the shaft that starts the mechanism. The motor can be:
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.
Motor design
Structurally, the motor from the “Indesit” washing machine is simple, but when designing a regulator for controlling its speed, it is necessary to take into account the parameters. Motors can be different in characteristics, due to which the control will also change. The mode of operation is also taken into account, on which the design of the converter will depend. Structurally, the collector motor consists of the following components:
- Anchor, it has a winding laid in the grooves of the core.
- Collector, mechanical rectifier of alternating voltage of the network, through which it is transmitted to the winding.
- Stator with excitation winding. It is necessary to create a constant magnetic field in which the armature will rotate.
With an increase in the current in the motor circuit, connected according to the standard scheme, the field winding is connected in series with the armature. With this inclusion, we also increase the magnetic field acting on the armature, which makes it possible to achieve linearity of characteristics. If the field remains unchanged, then it is more difficult to obtain good dynamics, it does not already mean large losses of power. Such motors are best used at low speeds, since they are more convenient to control at small discrete movements.
By organizing separate control of the excitation and the armature, it is possible to achieve high positioning accuracy of the motor shaft, but the control circuit will then become significantly more complicated. Therefore, we will take a closer look at the regulator, which allows you to change the rotation speed from 0 to the maximum value, but without positioning. This can be useful if a full-fledged drilling machine with the ability to cut threads will be made from the engine from the washing machine.
Lossless collector motor speed controller
Many types of work on wood, metal or other types of materials do NOT require high speeds, but good traction. It would be more correct to say. the moment. It is thanks to him that the planned work can be performed efficiently and with minimal power loss. For this, DC motors (or collector motors) are used as a driving device, in which the supply voltage is rectified by the unit itself. Then, to achieve the required performance, it is necessary to adjust the speed of the collector motor without losing power.
How to make a collector motor speed controller?
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 action of 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 a possible burnout of the instrument. If the rotation speed is too high, the performance of the tool may also become less predictable. How to fix it? For this purpose, it is customary to use a special speed controller.
A motor for power tools and household appliances usually falls into one of 2 main types:
- Collector motors.
- Asynchronous motors.
In the past, the second of these categories was most prevalent. Now, about 85% of the motors that are used in electrical tools, household or kitchen appliances are of the commutator type. This is explained by the fact that they have a greater degree of compactness, they are more powerful and the process of managing them is simpler.
The action of any electric motor is based on a very simple principle: if a rectangular frame is placed between the poles of a magnet, which can rotate around its axis, and a direct current is sent through it, the frame will turn. The direction of rotation is determined according to the “right hand rule”.
This pattern can be used for the operation of a collector motor.
The important point here is the connection of current to this frame. Since it rotates, special sliding contacts are used for this. After the frame rotates 180 degrees, current flows through these contacts in the opposite direction. Thus, the direction of rotation remains the same. At the same time, smooth rotation will NOT work. To achieve this effect, it is customary to use several dozen frames.
Drill speed control circuit
The figure below shows the circuit of the electric motor speed controller of the drill, assembled as a separate external unit and suitable for any drills with a capacity of up to 1.8 kW, as well as for other similar devices in which an AC collector motor is used, for example, in angle grinders. The details of the regulator in the diagram are selected for a typical drill with a power of about 270 W, 650 rpm, voltage of 220 V.
The thyristor type KU202N is mounted on a radiator for the purpose of its normal cooling. To set the required speed of the electric motor, the regulator cord is connected to a 220 V power outlet, and the drill is already included in it. Then, move the variable resistance knob R to set the Required RPM for the old drill.
When working with a drill, periodically it is necessary to smoothly change its revolutions, but a simple decrease in the supply voltage leads to both a decrease in revolutions and a loss of power, the scheme proposed below is only for this drawback, since it uses regulation with feedback on the current of the electric motor, as a result with increasing load, the torque on the ED shaft increases.
The circuit uses capacitors with an operating voltage of at least 400 V, all resistances with a power of at least 1 W.
The presented scheme is simple enough to repeat even for novice radio amateurs. The components and parts required for assembly are cheap and readily available. It is recommended to assemble the structure in a separate box with a socket. Such a device can be used as a carrier with a typical power regulator
The principle of operation of this amateur radio homemade product is as follows, when the load is small, then the current flows small, and as soon as the load increases, the revolutions gradually increase.
Micro-assemblies LM317 are required to be mounted on a radiator. Diodes 1N4007 can be replaced with similar ones designed for a current NOT lower than 1A. The printed circuit board is made on one-sided fiberglass. Resistance R5 with power NOT lower than 2W, or wire.
A 12V power supply should have a small current margin. Resistor R1 set the required idle speed. Resistance R2 is necessary to set the sensitivity in relation to the load, it sets the required torque by increasing the number of revolutions of the micro drill. If you increase the capacity C4, then the delay time of high speed increases.
The diagram below makes it possible to assemble a very simple, cheap and useful regulator of rotation speed of a 12-volt microdrill for drilling holes in printed circuit boards in amateur radio practice.
LM555 microassembly is used as a pulse width modulator. The supply voltage for the PWM is reduced and stabilized using the LM7805 microcircuit). The precision 50kΩ P1 trimmer allows you to adjust the rotational speed of the drill. The field-effect transistor IRL530N is used as an output drive element and can switch current up to 27A. In addition, it has fast switching times and low resistance. The 1N4007 diode is needed to protect against EMF countermeasures. Alternatively, you can take the Schottky diode MBR1645.
PWM (Pulse Width Modulation) used in this design is an effective method of varying speed and power for all DC motors.
AC collector motors
These single-phase motors have a lower efficiency than DC motors, but due to their ease of manufacture and control circuits, they are most widely used in household appliances and power tools. They can be called “universal” because they are able to work with both AC and DC currents. This is due to the fact that when the alternating voltage is connected to the network, the direction of the magnetic field and current will change in the stator and rotor at the same time, and not causing a change in the direction of rotation. The reverse of such devices is carried out by reversing the polarity of the rotor ends.
Adjustment of the speed of a DC motor with a stator winding connected in series can be done in two ways:
- By connecting in parallel the stator of an adjusting device that changes the magnetic flux. However, this method is rather difficult to implement and is not used in household devices.
- Regulation (reduction) of revolutions by reducing the voltage. This method is used in almost all electrical devices. household appliances, tools, etc.
DIY electrician
DC motors with series excitation
The excitation winding of such an electric motor has a small number of turns of a thick wire, and when it is sequentially connected to the armature circuit, the current in the entire circuit will be the same. Electric motors of this type are more durable under overloads and therefore are most often found in household appliances.
DC motors with parallel excitation
The field winding (stator) in a parallel-excited motor consists of a large number of turns of a thin wire and is connected parallel to the rotor, the winding resistance of which is much lower. Therefore, to reduce the current during starting of electric motors with a power of more than 1 kW, a starting rheostat is included in the rotor circuit. With such a switching scheme, the control of the motor speed is carried out by changing the current only in the stator circuit, since the way of reducing the voltage across the Terminal is very NOT economical and requires the use of a high power regulator.
A little theory about the device and field of application of collector motors
Electric motors of this type can be direct or alternating current, with series, parallel or mixed excitation (for alternating current, only the first two types of excitation are used).
The collector motor consists of a rotor, stator, collector and brushes. The current in the circuit passing through the stator and rotor windings connected in a certain way creates a magnetic field that makes the latter rotate. The voltage is transmitted to the rotor by means of brushes made of a soft electrically conductive material, most often it is graphite or a copper-graphite mixture. If you change the direction of the current in the rotor or stator, the shaft will start to rotate in the other direction, and this is always done with the rotor leads, so that there is NO reversal of the magnetization of the cores.
If the connection of both rotor and stator is changed at the same time, reversal will NOT occur. There are also three-phase collector motors, but that’s a whole other story.
Proelectrika.com. DIY electrician. How to reduce the speed of the electric motor
Adjusting the speed of the electric motor is often necessary both for production and for some kind of domestic purposes. In the first case, industrial voltage regulators are used to decrease or increase the speed of rotation. inverter frequency converters. And with the question of how to regulate the speed of the electric motor at home, let’s try to figure it out in more detail.
It must be said right away that for different types of single-phase and three-phase electrical machines, different power regulators must be used. Those. For asynchronous machines, the use of thyristor regulators, which are the main ones for changing the rotation of collector motors, is unacceptable.
Electric motor speed controllers
Schemes for changing the speed of rotation of electric motors in most cases built on thyristor regulators, due to its simplicity and reliability.
The principle of operation of the presented circuit is as follows: the capacitor C1 is charged to the breakdown voltage of the dynistor D1 through the variable resistor R2, the dynistor breaks through and opens the triac D2, which controls the load. The voltage across the load depends on the opening frequency D2, which in turn depends on the position of the variable resistance slider. This circuit is not equipped with feedback, i.E. When the load changes, the revolutions will also change and they will have to be adjusted. The same scheme is used to control the turnover of imported household vacuum cleaners.