Smooth start diagram for a drill. Do-it-yourself soft start for power tools. Making a speed controller
Sometimes failures of hand-held power tools - grinders, electric drills and jigsaws - are often associated with their high starting current and significant dynamic loads on gearbox parts that occur when the engine is suddenly started.
The soft start device for a collector motor described in is complex in terms of the scheme, it has several precision resistors and it requires painstaking adjustment. Using the KR1182PM1 phase regulator microcircuit, it was possible to make a much simpler device for a similar purpose that does not require adjustment. Anyone can be connected to it without any modification. hand power toolpowered by single-phase network 220 V, 50 Hz. The engine is started and stopped by the switch of the power tool, and in its off state the device does not consume current and can remain connected to the network indefinitely.
The diagram of the proposed device is shown in the figure. The XP1 plug is plugged into the mains socket, and the power tool plug is inserted into the XS1 socket. Multiple sockets can be installed and connected in parallel for alternating instruments.
When the motor circuit of the power tool is closed by its own switch, voltage is applied to the DA1 phase regulator. The charging of the capacitor C2 begins, the voltage across it gradually increases. As a result, the turn-on delay of the internal thyristors of the regulator, and with them the VSI triac in each subsequent half-cycle of the mains voltage, decreases, which leads to a smooth increase in the current flowing through the motor and, as a consequence, an increase in its speed. With the capacitance of the capacitor C2 indicated on the diagram, acceleration of the electric motor to maximum speed takes 2 ... 2.5 s, which practically does not create a delay in operation, but completely eliminates thermal and dynamic shocks in the tool mechanism.
After the engine is turned off, the capacitor C2 is discharged through the resistor R1. and after 2 ... 3 sec. everything is ready to restart. By replacing the fixed resistor R1 with a variable one, you can smoothly regulate the power supplied to the load. It decreases with decreasing resistance.
Resistor R2 limits the current of the control electrode of the triac, and capacitors C1 and C3 are elements of a typical circuit for switching on the DA1 phase regulator.
All resistors and capacitors are soldered directly to the pins of the DA1 microcircuit. Together with them, it is placed in an aluminum housing from the starter of a fluorescent lamp and is filled with epoxy compound. Only two wires are brought out, connected to the terminals of the triac. Before pouring, a hole was drilled in the lower part of the case, into which the screw MZ was threaded outward. With this screw, the unit is fixed on the heat sink of the VS1 triac with an area of \u200b\u200b100 cm ". This design has proved to be quite reliable when operating in high humidity and dusty conditions.
The device does not require any adjustment. Any triac can be used, with a voltage class of at least 4 (that is, with a maximum operating voltage of at least 400 V) and with a maximum current of 25-50 A. Thanks to the smooth start of the motor, the starting current does not exceed the rated one. The reserve is only needed in case of a jammed tool.
The device has been tested with power tools up to 2.2 nkW. Since the DA1 regulator ensures the current flow in the control electrode circuit of the VS1 triac during the entire active part of the half-cycle, there is no limitation on the minimum load power. The author even connected the "Kharkov" electric razor to the manufactured device.
K. Moroz, Nadym, YaNAO
LITERATURE
1. Biryukov S. Automatic smooth start of collector electric motors - Radio 1997, N * 8.s 40 42
2. Nemich A. Microcircuit KR1182PM1 - phase power regulator - Radio 1999, N "7, p. 44-46.
Everyone who has been using a grinder for more than one year, it broke. At first, each craftsman tried to repair the sparkling grinder on his own, hoping that it would work after replacing the brushes. Usually, after such an attempt, the broken tool remains on the shelf with burned-out windings. And a new grinder is bought to replace it.
Drills, screwdrivers, rotary hammers, milling cutters are necessarily equipped with a speed controller. Some so-called calibration grinders are also equipped with a regulator, while conventional grinders only have a power button.
Manufacturers do not deliberately complicate low-power grinders with additional circuits, because such a power tool should be cheap. It is clear, of course, that the service life of an inexpensive tool is always shorter than that of a more expensive professional one.
The most simple grinder can be upgraded so that the gearbox and armature winding wires are no longer damaged. These troubles mainly occur with a sharp, in other words, shock start of the grinder.
All modernization consists in just assembling the electronic circuit and fixing it in the box. In a separate box because there is very little space in the grinder handle.
A proven, working diagram is laid out below. It was originally intended to adjust the incandescence of lamps, that is, to work on an active load. Its main advantage? simplicity.
- The highlight of the soft starter, the schematic diagram of which you see, is the K1182PM1R microcircuit. This microcircuit is highly specialized, of domestic production.
- The acceleration time can be increased by choosing a larger capacitor C3. While charging this capacitor, the electric motor picks up speed to the maximum.
- There is no need to replace the resistor R1 with a variable resistance. The 68 kΩ resistor is optimally matched to this circuit. With this setting, you can smoothly start a grinder with a power of 600 to 1500 watts.
- If you are going to assemble a power regulator, then you need to replace the resistor R1 with a variable resistance. A resistance of 100 kOhm and more does not lower the output voltage. By short-circuiting the legs of the microcircuit, you can completely turn off the connected grinder.
- By inserting a semiconductor VS1 of the TC-122-25 type, that is, at 25A, into the power circuit, you can smoothly start almost any commercially available grinder with a power from 600 to 2700 W. And there is a large margin of power in the event of a grinding machine jamming. To connect grinders with a power of up to 1500 W, imported semistors BT139, BT140 are enough. These less powerful electronic keys are cheaper.
The semistor in the above circuit does not open completely, it cuts off about 15V of the mains voltage. Such a voltage drop does not affect the operation of the grinder in any way. But when the semistor heats up, the revolutions of the connected instrument are greatly reduced. This problem is solved by installing a radiator.
This simple circuit has another drawback - its incompatibility with the speed control installed in the instrument.
The assembled circuit must be hidden in a plastic box. An insulating housing is important because you need to protect yourself from mains voltage. You can buy a junction box at an electrical store.
A socket is screwed to the box and a cable with a plug is connected, which makes this design look like an extension cord.
If experience allows and there is a desire, you can assemble a more complex soft start circuit. The schematic diagram below is standard for the XS – 12 module. This module is installed in the power tool at the factory.
If you need to change the speed of the connected electric motor, then the circuit becomes more complicated: a trimmer is installed at 100 kΩ, and an adjusting resistor at 50 kΩ. Or you can simply and roughly introduce a 470 kOhm variable between the 47 kOhm resistor and the diode.
In parallel with capacitor C2, it is desirable to connect a 1 MΩ resistor (it is not shown in the diagram below).
The supply voltage of the LM358 microcircuit is in the range from 5 to 35V. The voltage in the power supply circuit does not exceed 25V. Therefore, you can do without an additional Zener diode DZ.
Whichever softstarter you build, never run a connected tool under load. Any soft start can be burned if you hurry. Wait for the grinder to unwind, and then work.
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I had never made a soft starter before. Purely theoretically, I imagined how to implement this function on a triac, although this option is not without drawbacks - power loss and a heat sink is required.
Wandering through the dusty Chinese storage facilities, in vain attempts to find something worthwhile, but not expensive, in the deposits of counterfeit and illiquid products, I came across this product.
Blah blah blah
The purchase was not for the sake of buying, but a conscious need. I decided to write a review on the table to put manual frezer... And I have it without a smooth start, it starts abruptly, self-destructing and destroying the environment around it. Soft start and soft start are not the same thing? Of course, there were doubts, although I had nothing to do with thermistors, I saw them only in computer power supplies, I always thought that they react to "surges and surges", that is, quickly, but "the voltage to rise slowly" and "after about five seconds ”created a worm of doubt. Moreover, and "or other high starting current machine applications."
Since the lack of knowledge makes us wasteful and decisive, I ordered this device and did not regret it for a second.
Here is what the seller writes about him:
A soft start power supply for a Class A amplifier, promising: 4 kW of power and 40 A through relay contacts at 150 V to 280 V AC. Dimensions 67 mm x 61 mm x 30 mm, the seller calls it ultra-small - aha -Ha. As if my current cutter falls into the frame, even if we divide the Chinese amperes by two, but in this size, the board is not pushy inside the tool case.
And, yes, it's a constructor. Need to solder!
The goods came in this form, plus, for better preservation, it was wrapped in a piece of newspaper in Chinese / Korean / Japanese, which disappeared, the survey of households and numerous servants did not clarify who and for what needs this piece was needed, so there is no photo of the newspaper, on top there was another bag without any pimples.
Soldering is easy - everything is drawn and signed.
Fee - can someone come in handy
Soldered:
back side
Sketched schematic diagram
How it works: when R2 is turned on, the resistance is large, the voltage across the load is less than 220 V, the thermistor heats up, its resistance tends to zero, and the voltage across the load to 220 V. Accordingly, the engine picks up speed.
At the same time, the rectified and stabilized VD2 voltage (24 V, although according to the first datasheet it should be 25, but volts there, volts here ...) feeds the relay switching circuit. Capacitor C3 is charged through R1, the capacity of which determines the relay response time. After 5 seconds, the transistor VT2 opens, the relay contacts shunt thermistor R2 and the engine operates at maximum power.
It was smooth on paper ... In reality, the connection of this device does not provide any smooth start to the engine, the thermistor heats up instantly, the motor immediately thrashes how much in vain, only the relay clicks mockingly after 5 seconds. I tried a 150 W motor - the same effect.
Blah-bpa-blah
He scolded the Chinese merchant. The pets, preschoolers, and co-workers who were watching the experiment scattered and hid in the dark corners, the mother-in-law took a pestle out of her sleeve just in case. But do not mislead gullible Russian buyers. He finished the odonka from the bottle left over from the coronation before last, took a bite of cold kulebyak, calmed down ... He took out the board from the garbage bucket, took off the sunflower husk from it.
“If a job fails, then every attempt to save it will make matters worse,” says Edward Murphy. “Too many people break down without even realizing how close to success they were at the moment they lost heart,” Thomas Edison argues with him. These two quotes have nothing to do with the case, they are given here to show that the author of the report is not just a freebie and stupid consumer of Chinese goods, but a well-read person, a pleasant conversationalist and intellectual. Feegley. But to the point.
A pair of K1182PM1R microcircuits were lying around in my closet on the mezzanine in a hat box.
Extract from the datasheet:
Direct use of ICs - for smoothly turning on and off electric incandescent lamps or adjusting their brightness. IP can also be used successfully for adjusting the rotation speed of electric motors up to 150 W (e.g. fans) and to control more powerful power devices (thyristors).
On one of them, I assembled a soft starter, which is not without flaws, but works as it should.
C1 sets the soft start time, R1 sets the voltage across the load. I got the maximum voltage at 120 ohms. At C1 100 uF, the acceleration time is about 2 seconds. By changing R1 to a variable one, you can adjust the speed of the collector motor, without feedback, of course (although this is implemented on the vast majority of the power tools sold). Triac VS1 any found, suitable for power. I have a BTA16 600B lying around.
back side
Everything is working.
Now it remains to cross two devices that complement each other, nullifying the disadvantages inherent in each separately.
Blah blah blah
In principle, the task is not difficult for a lively, inquiring mind. I removed the thermistor and threw it away until better times, in its place I soldered two wires coming from the cathode and the anode of the triac of the second board. I reduced the capacitance C3 on the first board to 22 μF, so that the relay would close the cathode and anode of the triac not after 5 seconds, but after about two.
At an air temperature of 30 degrees. With the temperature of the diode bridge 50 degrees, the Zener diode 65 degrees, the relay 40 degrees.
That's it - the alteration is over.
Blah blah blah
Another, less confident in his abilities, would be delighted with the result, throw a feast like a mountain, arrange a holiday with bears and gypsies. I just opened a bottle of champagne, made the girls dance in round dances in the yard and canceled the Saturday flogging.
It remains only to arrange all this in the case, I already wanted to, but for some reason there is no metal plate at home with which the case will be attached to the table. Everything will look something like this:
My conclusions are ambiguous, estimates are biased, recommendations are questionable.
Everything was tired, and these cats were always climbing into the frame - I was tortured to drive. I plan to buy +21 Add to favourites I liked the review +92 +163
Who wants to strain, spend their money and time on re-equipping devices and mechanisms that already work great? As practice shows - to many. Although not everyone in life is faced with industrial equipment equipped with powerful electric motors, they constantly encounter, albeit not so voracious and powerful, electric motors in everyday life. Well, everyone probably used the elevator.
Are motors and loads a problem?
The fact is that virtually any electric motors, at the time of starting or stopping the rotor, experience huge loads. The more powerful the engine and the equipment it propels, the greater the cost of starting it.
Probably the most significant load on the engine at the moment of start-up is the multiple, albeit short-term, excess of the rated operating current of the unit. After a few seconds of operation, when the electric motor reaches its nominal speed, the current consumed by it will also return to its normal level. To ensure the required power supply have to increase the capacity of electrical equipment and conductive lines, which leads to their rise in price.
When a powerful electric motor is started, due to its high consumption, there is a "drop" in the supply voltage, which can lead to malfunctions or failure of equipment supplied with it from the same line. In addition, the service life of the power supply equipment is reduced.
In the event of abnormal situations resulting in engine burnout or severe overheating, properties of transformer steel may change so much so that after repair the engine will lose up to thirty percent of its power. Under such circumstances, it is already unusable for further use and requires replacement, which is also not cheap.
What is a soft start for?
It would seem that everything is correct, and the equipment is designed for this. But there is always a "but". In our case, there are several of them:
- at the time of starting the electric motor, the supply current can exceed the nominal four and a half to five times, which leads to significant heating of the windings, which is not very good;
- starting the motor by direct switching leads to jerks, which primarily affect the density of the same windings, increasing the friction of the conductors during operation, accelerating the destruction of their insulation and, over time, can lead to an interturn short circuit;
- the aforementioned jerks and vibrations are transmitted to the entire driven machine. This is already completely unhealthy, because may damage its moving parts: gear systems, drive belts, conveyor belts, or just imagine yourself riding in a twitching elevator. In the case of pumps and fans, this is the risk of deformation and destruction of turbines and blades;
- you should also not forget about the products that may be on the production line. They can fall, crumble or break due to such a jerk;
- well, and probably the last of the points worthy of attention is the cost of operating such equipment. We are talking not only about expensive repairs associated with frequent critical loads, but also about a tangible amount of inefficiently consumed electricity.
It would seem that all of the above operating difficulties are inherent only in powerful and bulky industrial equipment, however, this is not the case. All this can be a headache for any average layman. This primarily applies to the power tool.
The specifics of the use of such units as jigsaws, drills, grinders and the like, imply multiple start and stop cycles, within a relatively short period of time. Such a mode of operation affects their durability and energy consumption to the same extent as their industrial counterparts. With all this, do not forget that soft start systems cannot regulate the operating speed of the motor or reverse their direction. It is also impossible to increase the starting torque or reduce the current lower than that required to start the rotation of the rotor of the electric motor.
Video: Soft start, regulation and protection of the collector. engine
Options for soft start systems for electric motors
Star-delta system
One of the most widely used industrial induction motor starting systems. Its main advantage is simplicity. The engine starts when the star system windings are commuted, after which, when the nominal speed is set, it automatically switches to the delta commutation. This start option allows you to achieve a current almost a third lowerthan when starting the electric motor directly.
However, this method is not suitable for mechanisms with low rotational inertia. These include, for example, fans and small pumps, due to the small size and weight of their turbines. At the moment of transition from the configuration "star" to "triangle", they will sharply reduce the speed or even stop. As a result, after switching, the electric motor essentially restarts. That is, in the end, you will not achieve not only saving the engine resource, but, most likely, you will get an overconsumption of electricity.
Video: Connecting a three-phase asynchronous electric motor with a star or delta
Electronic system of soft start of the electric motor
A soft start of the engine can be carried out using triacs included in the control circuit. There are three schemes for such an inclusion: single-phase, two-phase and three-phase. Each of them differs in its functionality and final cost, respectively.
With the help of such schemes, usually, it is possible to reduce the starting current up to two or three nominal. In addition, it is possible to reduce the significant heating inherent in the aforementioned star-delta system, which helps to increase the life of the electric motors. Due to the fact that the engine start-up is controlled by reducing the voltage, the rotor accelerates smoothly, and not abruptly, like with other circuits.
In general, several key tasks are assigned to engine soft start systems:
- main - lowering the starting current to three or four rated;
- reduction of the motor supply voltage, if appropriate capacities and wiring are available;
- improving the parameters of starting and braking;
- emergency network protection against overcurrent.
Single-phase starting circuit
This circuit is designed to start electric motors with a capacity of no more than eleven kilowatts. This option is used in the event that it is required to soften the shock at start-up, and braking, soft start and lowering the starting current do not matter. First of all, because of the impossibility of organizing the latter, in such a scheme. But due to the reduction in the cost of production of semiconductors, including triacs, they are discontinued and are rarely found;
Two-phase starting scheme
This circuit is designed to regulate and start motors up to two hundred and fifty watts. Such soft starters sometimes equipped with a bypass contactor to reduce the cost of the device, however, this does not solve the problem of asymmetry in the supply of phases, which can lead to overheating;
Three-phase starting scheme
This circuit is the most reliable and versatile soft-start system for electric motors. The maximum power of the motors controlled by such a device is limited exclusively by the maximum temperature and electrical endurance of the triacs used. Him versatility allows you to implement a lot of functionssuch as: dynamic brake, retraction catch or balancing of magnetic field and current limitation.
An important element of the last mentioned circuit is the bypass contactor, which was mentioned earlier. is he allows you to ensure the correct thermal mode of the soft start system of the electric motor, after the engine reaches its normal operating speed, preventing its overheating.
The existing soft starters of electric motors, in addition to the above properties, are designed for their joint operation with various controllers and automation systems. They have the ability to turn on at the command of the operator or the global control system. Under such circumstances, at the moment the loads are switched on, interference may appear that can lead to malfunctions in the operation of the automation, and therefore, it is worth taking care of the protection systems. The use of soft start schemes can significantly reduce their impact.
Do-it-yourself smooth start
Most of the systems listed above are actually inapplicable in a domestic environment. First of all, for the reason that we rarely use three-phase asynchronous motors at home. But there are more than enough collector single-phase motors.
There are many schemes for smooth engine start devices. The choice of a specific one depends solely on you, but in principle, having some knowledge of radio engineering, skillful hands and desire, quite you can assemble a decent homemade starterwhich will prolong the life of your power tool and household appliances for years to come.
Many power tools fail due to motor wear. Modern models of grinders have a soft starter. Due to him, they are ways to work for a long time. The principle of operation of the element is based on changing the operating frequency. In order to learn more about the starter device, it is worth considering the diagram of the standard model.
Soft starter
The standard Bulgarian soft start circuit consists of a triac, a rectifier and a set of capacitors. To increase the operating frequency, resistors are used that pass current in one direction. The starter is protected by a compact filter. low is supported for models. However, in this case, much depends on the maximum power of the motor, which is installed in the grinder.
How to connect a model?
The connection of the soft start of the grinder is carried out through an adapter. Its input contacts are connected to the rectifier unit. In this case, it is important to determine the zero phase in the device. To fix the contacts, you will need to Check the performance of the starter through the tester. First of all, negative resistance is determined. When installing the starter, it is important to remember the threshold voltage that the device can withstand.
Diagram of a device for a grinder with a 10 A triac
The diagram of a soft start of a grinder, made by hand, involves the use of contact resistors. The polarity ratio of modifications, as a rule, does not exceed 55%. Many models are manufactured with blockers. A wired filter is responsible for protecting the device. Low frequency transceivers are used to pass the current. The process of lowering the threshold voltage is carried out on a transistor. The triac in this case acts as a stabilizer. When connecting the model, the output resistance at an overload of 10 A should be about 55 ohms. Starter covers are semiconductor based. In some cases, magnetic transceivers are installed. They handle low RPM well and can maintain the rated frequency.
Model for grinders with 15 A triac
Soft start for a grinder with 15 A triacs is universal and is often found in low-power models. The difference between the devices is low conductivity. The scheme (device) of the soft start of the grinder involves the use of contact-type transceivers that operate at a frequency of 40 Hz. Many models use comparators. These elements are installed with filters. The rated voltage of the starters starts from 200 V.
Starters for grinders with a 20 A triac
Devices with 20 A triacs are suitable for professional grinders. Many models use contactor resistors. They are primarily capable of operating at high frequencies. The maximum temperature of the starters is 55 degrees. Most models have a well-protected case. The standard scheme of the device assumes the use of three contactors with a capacity of 30 pF. Experts say the devices stand out for their conductance.
The minimum frequency for starters is 35 Hz. They are capable of working in a DC network. Modifications are connected via adapters. Such devices are well suited for 200 W motors. Filters are often installed with triodes. Their sensitivity index is no more than 300 mV. Wired comparators with a protection system are quite common. If we consider imported models, then they have an integral converter that is installed with insulators. Current conductivity is provided at around 5 microns. With a resistance of 40 ohms, the model is able to consistently maintain high revs.
Models for the grinder 600 W
For 600 W grinders, starters with contact triacs are used, for which the overload does not exceed 10 A. It is also worth noting that there are many devices with plates. They stand out for their security and are not afraid of high temperatures. The minimum frequency for 600 W grinders is 30 Hz. In this case, the resistance depends on the installed triode. If it is used of a linear type, then the above parameter does not exceed 50 ohms.
If we talk about duplex triodes, then the resistance at high speeds can reach up to 80 ohms. It is very rare for models to have stabilizers that work from comparators. Most often they are attached directly to modules. Some modifications are made with wired transistors. Their minimum frequency starts from 5 Hz. They are afraid of overloads, but they are able to maintain high speed at
Devices for 800 W grinders
800 W grinders work with low frequency starters. Triacs are quite often used at 15 A. If we talk about the model circuit, then it is worth noting that they use expansion transistors, in which the current carrying capacity starts from 45 microns. Capacitors are used with and without filters, and the capacitance of the elements is no more than 3 pF. It is also worth noting that starters differ in sensitivity.
If we consider professional grinders, then 400 mV modifications are suitable for them. In this case, the current conductivity can be low. There are also devices with variable transistors. They quickly warm up, but they are not able to maintain the high speed of the grinder, and their current conductivity is about 4 microns. If we talk about other parameters, then the nominal voltage starts from 230 V. The minimum frequency for models with broadband triacs is 55 Hz.
Starters for grinders 1000 W
Starters for these grinders are made on triacs with an overload of 20 A. The standard device circuit includes a triode, a stabilizer plate and three transistors. The rectifier unit is most often installed on a wired basis. Capacitors can be used with or without a filter. The minimum frequency of the conventional model is 30 Hz. At 40 ohms, the starters are capable of supporting high overloads. However, problems can arise at low speeds of the grinder.
How to make a starter from a TC-122-25 triac?
It is quite simple to make a smooth start for a grinder with your own hands with a TC-122-25 triac. First of all, it is recommended to prepare a contactor resistor. Capacitors will require a single pole type. In total, three elements are installed in the starter. The capacity of one capacitor should not exceed 5 pF. To increase the operating frequency, a contactor is soldered on the plate. Some experts say that filters can improve conductivity.
The rectifier unit is used with a conductivity of 50 microns. It is capable of withstanding large overloads and will be able to provide high rpm. Further, in order to assemble a smooth start on the grinder with your own hands, a thyristor is installed. At the end of the work, the model is connected via an adapter.
Assembling a model with triacs of the VS1 series
You can assemble a soft start for a grinder on a VS1 triac with your own hands using several rectifier blocks. Capacitors for the device are suitable for linear type with a capacity of 40 pF. It is worth starting the assembly of the modification by soldering the resistors. Capacitors are installed in series between insulators. The rated voltage of a quality starter is 200 V.
Further, in order to make a smooth start for the grinder with your own hands, the prepared triac is taken and soldered at the beginning of the circuit. Its minimum operating frequency should be 30 Hz. In this case, the tester must show a value of 50 ohms. If there are problems with overheating of the capacitors, then dipole filters should be used.
Model for grinders with KR1182PM1 regulator
To assemble a soft start for the grinder with your own hands with the KR1182PM1 regulator, a contact thyristor and a rectifier unit are taken. It is more expedient to use a triode for two filters. It is also worth noting that three capacitors with a capacity of at least 40 pF are required to assemble the starter.
The sensitivity index for the elements must be 300 mV. Experts say that the triac can be installed behind the cover. It should also be remembered that the threshold voltage should not fall below 200 V. Otherwise, the model will not be able to work at a reduced speed of the grinder.