Smooth start and adjustment of angle grinder speed. Do-it-yourself soft start for an angle grinder. Connection diagram for a soft start for an angle grinder.

A grinder, or grinding machine, is often simply necessary on the farm to perform metal work. In addition, it can be used to clean both wooden and stone materials. It is difficult to imagine performing industrial work without an angle grinder. This is a tool that is suitable for both a professional in his work and an amateur in household work.

When doing work with your own hands, it is important that the power tool has a smooth start. This is especially true if you often have to work, and the network cannot withstand the voltage of the tool.

Budget options for angle grinders - angle grinders - have a number of disadvantages:

The power tool does not have the ability to have a smooth, soft start. This can lead to power outages, since the angle grinder consumes a large amount of electricity in the first seconds after switching on. There is also a huge probability of damage to the electric motor and breakage of the tool after not a soft start, but a sharp, jerky one.
Power tools, especially simple Chinese ones, do not have a speed regulator (by adjusting the speed you can ensure long operation of the tool without putting a load on it).

Therefore, when choosing a tool, it is very important to pay attention to such parameters as speed control and the presence of a soft start. In addition, when choosing an angle grinder, you should pay attention to power. The main indicator here is the volume of work performed.

If the work is not large-scale and not frequent at the household level, then a power tool with an adjustment of 125 mm and a power of between 600-900 W is suitable.

For large-scale work on an industrial scale, you should use an angle grinder that is approximately twice as powerful. In addition to technical characteristics, one of the main indicators is safety. The grinder must be safe. What does it mean? Firstly, as already mentioned, the presence of a soft start, which prevents voltage surges during switching on. Automatic fuses necessary for emergency stop of the motor during a system failure. The fuses serve as a regulator when the circle jams. Provides protection from dust. It is necessary when using an angle grinder frequently to prevent dust from accumulating in the tool.

The heat dissipation function is important. The heat sink protects against overheating. During operation, especially if the work is prolonged, the machine body is subject to strong heating so that there is no overheating and heat removal is necessary. When overloaded, the angle grinder stops - this happens during heating, approaching 200 o C. Well, balancing the disk serves to reduce unpleasant vibration and beating of the tool during operation, old worn disks are especially susceptible to this effect. Paying attention and paying attention to safety when choosing a tool and when further working with it is very important.

When choosing a tool, it is worth noting that there are grinders with one and two handles. Here you should rely solely on convenience. Two-handed models will most likely be more comfortable to hold, however, such tools are heavier in weight; one-handed models will also have to be held with two hands, but such angle grinders are smaller in size and weight.

Bosch is the leader in the power tools market. The tools of this company have all the necessary characteristics from convenience to safety. Another advantage of Bosch tools is that there is good ventilation.

Bt136 600E: voltage regulation switching circuit

Manufacturers do not burden cheap angle grinders that do not have sufficient power with voltage control switching circuits, otherwise such angle grinders would no longer be cheap. When starting the grinder, if it is smooth, the process is carried out through an adapter connected by contacts to the rectifier block. The rectifier block converts the current.

But sometimes it makes sense to modernize an angle grinder using an established scheme. The electrical circuit is assembled quite simply. It is not difficult to make, and you can, if desired, connect not only an angle grinder, but any other tool to the finished circuit. However, the tool must have a commutator motor, not an asynchronous one.

A homemade approach to creating a circuit would be as follows:

To get started, you should download the board if you don’t have it;
The Bt136 600E triac is used as the power link;
During operation, the triac will heat up; to avoid this, a heat sink is installed;
The resistors used provide resistance to current, providing current suppression;
The regulator is adjusted using a multi-turn trimmer resistor;
To check, you should connect a light bulb;
After connecting, the light bulb must be turned off - the triac must be cold;
Connecting the resulting circuit to the grinder.

If the board is connected correctly, the triac and resistors of the angle grinder should start smoothly, and the use of the rotation speed should be regulated. After this, you can test the grinder in action. Such knowledge may be needed when repairing electric motor faults. For example, when voltage increases or improper balancing occurs.

Do-it-yourself speed controller for an angle grinder

If you use your ingenuity to create a speed controller with your own hands, you can use soldered control boards from a sewing machine or vacuum cleaner. In addition, the components for the regulator are inexpensive and can be easily purchased if possible. It is worth noting that the device requires a gearbox to support a certain number of revolutions and speed. If the speeds are high, then the reason is most likely in the stator. The stator requires repair. Repairing the stator is possible at home.

The operation of the commutator motor is ensured by any type of electrical voltage. When changing the voltage power, you need to reduce or increase the number of revolutions. The thyristor speed controller helps to change this number.

Regulator assembly steps:

First, you need to unscrew the handle of the grinder, evaluate the place and figure out where to place the elements of the circuit (if there is no space, then you can make the device in a separate box);
The resistor can be made of aluminum;
Provided the triac does not heat up too much, a small radiator is sufficient;
Next, the structure is soldered.

Finally, it is glued with epoxy resin to secure it. A homemade device can work for years. There are cases when the device accelerates at higher speeds after switching on - this means the stator winding is short-circuited. In this case, a turn short circuit occurred. The stator requires repair, most often it requires rewinding.

What are the typical malfunctions: the winding breaks or burns, a short circuit occurs, the insulating surface breaks through.

Making a speed controller

An electric angle grinder is impossible without a speed controller, so that it is possible to reduce the speed.

The regulator circuit from a physics point of view looks like this:

Resistor – R1;
Trimmer resistor – VR1;
Capacitor – C10;
Triac - DIAC;
Triac - TRIAC.

The electronic regulator can be not only built-in, but also remote for convenience. In Bosch angle grinders, the electronics set the speed from almost 3 thousand to 11.5 thousand. There is no load on the meter's power, all indicators are taken into account. Reducing the number of revolutions and increasing them is not difficult for the tool. Adjustable rotation speeds are simply necessary when working with an angle grinder.

Making a soft start for a power tool with your own hands (video)

Only at first glance, it seems that an angle grinder may never be needed in life, that situations when it will come in handy, much less when it will have to be repaired, will not arise. Of course, you can turn to professionals, or you can identify the problem yourself and try to fix it.

A smooth start for any power tool is very important for the following reasons. First, it helps protect your electrical device from breakdowns, which means fewer trips to the repair shop, which means virtually no downtime and increased productivity. Secondly, having a soft start for the electric motor saves you money that could otherwise be spent on paying repairmen or buying a new tool.

In contact with

This article will look at making a soft start for an electric motor with your own hands using the example of an angle grinder or, in other words, an angle grinder.

Why do you need a soft start unit?

Due to some design features, starting the grinder leads to the appearance of dynamic loads to the device. Since the mass of the disk with which useful work is carried out is quite high, powerful inertial forces act on the commutator motor and gearbox of the device, which leads to the following negative factors:

During the start, which is especially sharp, inertial forces very strongly influence the body of the device, which may cause injury: You simply don't hold the tool and release it. Therefore, when starting the electric motor of the angle grinder, always hold it with both hands.
During start-up, the electric motor is subject to an overload caused by the supply of high voltage. What does this lead to? First of all, the motor winding suffers and accelerated wear of the brushes occurs, which will not happen if you make a block for a soft start. Otherwise, be prepared for the fact that one not very wonderful day something will happen in the engine. short circuit caused by complete wear of the brushes. This, in turn, will force you to shell out money for repairs or buy a new sander.
Rapidly applying torque to the gearbox during startup will cause accelerated wear on the gears in your grinder's gearbox.
Also keep in mind that jumping the angle grinder can destroy the blade, the fragments of which can cause serious harm to you, so never work without a cover for protection.

To make it more clear to you which elements of the grinding machine suffer most from a sudden start, look at the diagram below.

Of course, some companies that produce grinding machines equip their devices with a soft start block at the factory. However, equipping with a soft start is an unaffordable luxury for angle grinders in the budget price segment, so if you do not want to buy an expensive power tool, then you are in danger of encountering the problems described above.

However, there is a way out and it is quite simple: make your own device for a soft start according to one of the possible schemes. If there is free space in the body of your device, then you can use a ready-made soft start device and put it in the grinder.

Making a soft start for an angle grinder with your own hands

One of the most commonly used schemes for manufacturing a starting device is based on chip KR118PM1 and triacs that make up the power section. Using this scheme, you can make a soft start unit without having specialized skills and without deep knowledge of electrical engineering. The only important thing is that you know how to solder.

Graphically, this diagram looks like this.

DIY device you can connect to absolutely any power tool, designed for a voltage of two hundred and twenty volts. Soft start block, created on the basis of this scheme, does not need to be turned on with a separate button, but can be connected to the standard button of the grinding machine. If your angle grinder has free space inside the case, you can install the unit in it or make a separate case for it and connect it to the power tool through a gap in the power cable.

The best option for connecting a soft starter unit and your grinder will be as follows: you apply voltage to the input of the block (connector XS1) from a power source with a voltage of two hundred and twenty volts. A plug from an angle grinder is connected to the output of the block (connector XP1).

Operating principle of the soft starter

After you press the power button on the grinder, voltage appears in the circuit, which is initially sent to the microcircuit, which is designated DA1 in the diagram above. The capacitor, which regulates the voltage, gradually increases it until the operating value is reached. Due to the operation of the capacitor, the thyristors in the microcircuit open with some delay and slowly transmit voltage to the power part in triacs VS1.
The process described above occurs in periods that become shorter and shorter if you count them from the moment of startup. As a result, the voltage supplied to the grinding machine increases slowly, and not abruptly, which determines the smooth start of the electric motor.
The time during which the engine reaches operating speed is depends on the capacity of the capacitor used C2. As a rule, a capacity equal to forty-seven microfarads is enough for the angle grinder to start smoothly in two seconds. Usually this period of time is enough to remove the overload from the electric motor and gearbox.
After you finish work and turn off your device, resistor R1 discharges capacitor C1 with its resistance. If the value of resistor R1 is sixty-eight kilo-ohms, then the discharge takes only three seconds. You can then use the soft starter again as it is ready to start the sander again.

If you want to upgrade the unit to a device regulating the speed of the electric motor, then replace the constant resistor R1 with a variable one. In this case, you can adjust its resistance, and therefore influence the engine speed.

Triac VS1 in your block must meet the following characteristics:

The minimum current it allows is twenty-five amperes.
The maximum voltage for which it is designed is four hundred volts.

This circuit, tested by many craftsmen, was tested on a grinder with a power equal to two kilowatts, and has a power safety margin of up to five kilowatts, which is made possible thanks to the KR118PM1 microcircuit.

If you have an old angle grinder in your arsenal, don’t rush to write it off. Using a simple electrical circuit, the device can be easily upgraded by adding the function of changing the speed. Thanks to a simple regulator that you can actually assemble with your own hands in a few hours, the functionality of the device will increase significantly. By reducing the rotation speed, the grinder can be used as a grinding and sharpening machine for various types of materials. New opportunities are emerging for the use of additional attachments and accessories.

Why does the grinder need low speeds?

The built-in disc speed control function allows you to delicately process materials such as plastic or wood. At low speeds, operating comfort and safety increases. This function is especially useful in electrical and radio installation practice, in car services and restoration workshops.

In addition, among professional users of power tools there is a strong opinion that the simpler the device is, the more reliable it is. And it is better to move the additional service stuffing outside the power unit. In this situation, equipment repair is greatly simplified. Therefore, some companies specially produce remote, separate electronic regulators that connect to the machine’s power cord.

Speed controller and soft start - what are they for?

Modern grinders use two important functions that increase the reliability and safety of the tool:

speed controller - a device designed to change the number of engine revolutions in various operating modes;
soft start - a circuit that ensures a slow increase in engine speed from zero to maximum when the device is turned on.

They are used in electromechanical tools that use a commutator motor in their design. Helps reduce wear on the mechanical part of the unit during switching on. They reduce the load on the electrical elements of the mechanism by putting them into operation gradually.

As studies of the properties of materials have shown, the most intense production of friction units occurs during a sharp transition from a state of rest to a mode of rapid movement. For example, one start of an internal combustion engine in a car is equivalent to 700 km of mileage in terms of wear on the piston group.

When the power is turned on, an abrupt transition occurs from a state of rest to rotation of the disk at a speed of 2.5–10 thousand revolutions per minute. Those who have worked with an angle grinder are well aware of the feeling that the machine simply “rips out of your hands.” It is at this moment that the overwhelming number of breakdowns associated with the mechanical part of the unit occur.

The stator and rotor windings experience no less load. The commutator motor starts in short circuit mode, the electromotive force is already pushing the shaft forward, but inertia does not yet allow it to rotate. A jump in starting current occurs in the coils of the electric motor. And although they are structurally designed for such work, sooner or later a moment comes (for example, during a power surge in the network) when the winding insulation cannot withstand and an interturn short circuit occurs.

When soft start circuits and changes in engine speed are included in the electrical circuit of the tool, all of the above problems automatically disappear. Among other things, the problem of voltage “dip” in the general network at the moment of starting a hand tool is solved. This means that the refrigerator, TV or computer will not be at risk of “burning out”. And the safety circuit breakers on the meter will not operate and cut off the current in the house or apartment.

The soft start circuit is used in angle grinders of medium and high price categories, the speed control unit is used mainly in professional models of angle grinders.

Adjusting the speed allows you to process soft materials with a grinder, perform fine grinding and polishing - at high speed, wood or paint will simply burn.

Additional electrical circuits increase the cost of the tool, but increase the service life and level of safety during operation.

How to assemble a regulator circuit with your own hands

The simplest power regulator, suitable for an angle grinder, soldering iron or light bulb, is easy to assemble with your own hands.

Electrical circuit diagram

In order to assemble a simple speed controller for an angle grinder, you need to purchase the parts shown in this diagram.

R1 - resistor, resistance 4.7 kOhm;
VR1 - trimming resistor, 500 kOhm;
C1 - capacitor 0.1 µF x 400 V;
DIAC - triac (symmetrical thyristor) DB3;
TRIAC - triac BT-136/138.

Circuit operation

Trimmer resistor VR1 changes the charging time of capacitor C1. When voltage is applied to the circuit, at the first moment of time (the first half-cycle of the input sinusoid), triacs DB3 and TRIAC are closed. The output voltage is zero. Capacitor C1 charges and the voltage across it increases. At a certain point in time, specified by the R1-VR1 chain, the voltage on the capacitor exceeds the opening threshold of the triac DB3, the triac opens. The voltage from the capacitor is transmitted to the control electrode of the TRIAC triac, which also opens. Current begins to flow through the open triac. At the beginning of the second half-cycle of the sinusoid, the triacs are closed until capacitor C1 is recharged in the opposite direction. Thus, the output produces a pulse signal of complex shape, the amplitude of which depends on the operating time of the C1-VR1-R1 circuit.

Assembly order

Assembling this circuit will not be difficult even for a novice radio amateur. Spare parts are available and can be purchased at any store. Including desoldering from old boards. The procedure for assembling the regulator using thyristors is as follows:

How to connect the device to an angle grinder, options

The connection of the regulator depends on what type of device is selected. If a simple circuit is used, it is enough to mount it into the power supply channel of the power tool.

Installing a homemade board

There are no ready-made installation recipes. Anyone who decides to equip an angle grinder with a regulator places it in accordance with their goals and model of the tool. Some people insert the device into the handle of the holder, others into a special additional box on the body.

In different models, the space inside the angle grinder body may be different. Some have enough free space to install a control unit. In others, you have to take it to the surface and attach it in a different way. But the trick is that, as a rule, there is always a certain cavity in the back of the instrument. It is designed for air circulation and cooling.

This is usually where the factory speed controller is located. A DIY diagram can be placed in this space. To prevent the regulator from burning out, the thyristors should be installed on the radiator.

Video: soft start plus and engine speed adjustment

Features of installation of the finished block

When purchasing and installing a factory regulator inside an angle grinder, most often you have to modify the body - cut a hole in it to allow the adjustment wheel to come out. But this may adversely affect the rigidity of the casing. Therefore, it is preferable to install the device outside.

The numbers on the adjustment wheel indicate the number of spindle revolutions. This value is not absolute, but conditional. “1” - minimum speed, “9” - maximum. The remaining numbers serve as a guide for regulation. The location of the wheel on the body varies. For example, on the Bosch PWS 1300–125 CE, Wortex AG 1213–1 E or Watt WWS-900 angle grinders, it is located at the base of the handle. On other models, such as the Makita 9565 CVL, the adjustment wheel is located at the end of the housing.

The connection diagram of the regulator to the angle grinder is not complicated, but sometimes it is not so easy to stretch the cables to the button, which is located at the other end of the device body. The problem can be solved by selecting the optimal wire cross-section or by placing it on the surface of the casing.

A good option is to install the regulator on the surface of the device or attach it to a network cable. Not everything always works out on the first try; sometimes the device has to be tested and then some adjustments made. And this is easier to do when access to its elements is open.

Important! If you have no experience working with electrical circuits, it is more advisable to purchase a ready-made factory regulator or angle grinder equipped with this function.

Device Instruction Manual

The basic rule when operating an angle grinder with a homemade speed controller is to adhere to the work and rest schedule. The fact is that an engine operating at a “regulated” voltage gets especially hot. When grinding at low speeds, it is important to take frequent breaks so that the commutator windings do not burn out.

It is also highly recommended not to turn on the tool if the speed regulator is set to minimum - the reduced voltage will not be enough to rotate the rotor, the collector lamellas will remain in short circuit mode, and the windings will begin to overheat. Unscrew the variable resistor to the maximum, then, turning on the angle grinder, reduce the speed to the desired value.

Following the correct order of activation and adjustment will allow you to operate the angle grinder for an unlimited period of time.

In addition, it should be understood that adjusting the speed of rotation on an angle grinder occurs on the principle of a water tap. The device does not increase the number of revolutions, it can only decrease them. It follows from this that if the maximum nameplate speed is 3000 rpm, then when a speed controller is connected, the angle grinder will operate in a range lower than the maximum speed.

Attention! If the angle grinder already contains electronic circuits, for example, it is already equipped with a speed controller, then the thyristor controller will not work. The internal circuits of the device simply will not turn on.

Video: homemade angle grinder speed controller

Equipping the angle grinder with a circuit for adjusting engine speed will increase the efficiency of using the device. and expand its functional range. This will also save the technological resource of the grinding machine and increase its service life.

A grinding machine, known in our country as a “grinder”, is very often useful on the farm when it is necessary to carry out metal work. This power tool can be used to clean wood and stone; It is impossible to imagine industrial work without a grinder. Even a non-professional can use this power tool.

Grinder with soft start and speed control

When doing work with your own hands using an angle grinder, it is important that it has a smooth start. This is especially true if you have to turn it on often, and the mains does not withstand the voltage of the power tool.

For budget options of angle grinders (angle grinders) the following disadvantages:

The tool does not have a soft start. Because of this, interruptions in the power supply may occur, because in the first seconds after turning on the angle grinder consumes a lot of electricity. There is a high probability of damage to the electric motor and failure of the tool after a sudden start.
Especially the Chinese angle grinder does not have a speed controller capable of ensuring long-term operation without stress on the tool.

When choosing an angle grinder, it is important to pay attention to the availability of speed control and soft start. Also, when choosing an angle grinder, they look at the power.

If large-scale work is not expected, a tool with an adjustment of 125 mm and a power in the range of 600-900 W is suitable. On an industrial scale, it is better to use an angle grinder, which is approximately twice as powerful.

The main indicator is safety!

There are grinders with one and two handles. Everyone chooses what is convenient for them. Two-handed instruments are perhaps more comfortable to hold, but they are heavier. One-handed models are also held with two hands, but they weigh less and are smaller in size.

The market leader in the described power tools is Bosch. Its products have all the required characteristics; comfortable, safe, with good ventilation.

Cheap models

Cheap, insufficiently powerful angle grinders are produced without voltage regulation circuits, otherwise they would not be cheap. When starting the grinder smoothly the process is carried out through an adapter, which is connected by contacts to the rectifier block. The device block converts the current.

Sometimes it is advisable to modernize an angle grinder using an established scheme. The electrical circuit is assembled quite simply. It is not difficult to make a diagram with your own hands. You can also connect another tool to the finished circuit that has a commutator rather than an asynchronous motor.

Creating a schema is as follows:

If the board, triac and resistors are connected correctly, the angle grinder should start smoothly, and the rotation speed should be regulated. Next, the tool can be tested in practice. This knowledge can be useful when repairing an electric motor, for example, when the voltage increases or there is improper balancing.

DIY speed controller

You can make a speed controller, using soldered control boards of a vacuum cleaner or sewing machine, although the parts of the device are inexpensive. The gearbox maintains a certain number of revolutions and speed. If the speeds are very high, the problem is most likely in the stator; this device requires repair. You can repair this device at home.

The operation of the commutator motor is ensured by any electrical voltage; When power changes, the number of revolutions decreases or increases. This number of times is changed using a thyristor speed controller.

Regulator assembly algorithm:

The handle is unscrewed, and you figure out where to place the circuit elements (if there is not enough space, the device is made in a separate box).
The resistor can be made of aluminum.
If the triac heats up slightly, a small radiator will suffice.
Soldering.
Gluing with epoxy resin.

This homemade device can last for years. Sometimes it accelerates after switching on at increased speeds, which indicates a short circuit in the stator winding. Most often the stator needs rewinding.

Typical malfunctions are:

winding rupture or burnout;
Breakdown of the insulating surface.

Manufacturing of speed controller

Using the speed controller we reduce the speed.

The diagram includes the following elements:

The electronic regulator can be remote. In Bosch angle grinders, the electronics set the number of revolutions from almost 3000 to 11500. There is no load on the meter’s power, every indicator is taken into account. Adjustable rotation speeds are necessary for any type of work.

The grinder is a very useful tool, and it’s good that there are no particular difficulties in quickly learning how to work with it!

Who wants to strain, spend their money and time on re-equipment of devices and mechanisms that already work perfectly? As practice shows, many do. Although not everyone in life encounters 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.

Electric motors and loads - a problem?

The fact is that virtually any electric motor, at the moment of starting or stopping the rotor, experiences enormous loads. The more powerful the engine and the equipment it drives, the greater the costs of starting it.

Probably the most significant load placed on the engine at the time of start-up is a multiple, albeit short-term, excess of the rated operating current of the unit. After just a few seconds of operation, when the electric motor reaches its normal speed, the current consumed by it will also return to normal levels. To ensure the necessary power supply have to increase the power of electrical equipment and conductive lines, which leads to their rise in price.

When starting a powerful electric motor, due to its high consumption, the supply voltage “drops”, which can lead to failures or failure of equipment powered from the same line. In addition, the service life of power supply equipment is reduced.

If emergency situations occur that result 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 no longer suitable for further use and requires replacement, which is also not cheap.

Why do you need a soft start?

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 moment of starting the electric motor, the supply current can exceed the rated one by four and a half to five times, which leads to significant heating of the windings, and this is not very good;
starting the engine by direct switching leads to jerks, which primarily affect the density of the same windings, increasing the friction of the conductors during operation, accelerates 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 unit. This is already completely unhealthy, because may cause damage to its moving parts: gear systems, drive belts, conveyor belts, or just imagine yourself riding in a jerking elevator. In the case of pumps and fans, this is the risk of deformation and destruction of turbines and blades;
We should also not forget about the products that may be on the production line. They may fall, crumble or break due to such a jerk;
Well, and probably the last point that deserves 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 significant amount of inefficiently spent electricity.

It would seem that all of the above operating difficulties are inherent only in powerful and bulky industrial equipment, however, this is not so. All this can become a headache for any average person. This primarily applies to power tools.

The specific use of such units as jigsaws, drills, grinders and the like require multiple start and stop cycles over a relatively short period of time. This operating mode 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 engine speed or reverse their direction. It is also impossible to increase the starting torque or reduce the current below that required to start rotating the motor rotor.

Video: Soft start, adjustment and protection of the commutator. engine

Options for soft start systems for electric motors

Star-delta system

One of the most widely used starting systems for industrial asynchronous motors. Its main advantage is simplicity. The engine starts when the windings of the star system are switched, after which, when the normal speed is reached, it automatically switches to delta switching. This is the starting option allows you to achieve a current almost a third lower than when starting an electric motor directly.

However, this method is not suitable for mechanisms with low rotational inertia. These, for example, include fans and small pumps, due to the small size and weight of their turbines. At the moment of transition from the “star” to the “triangle” configuration, they will sharply reduce the speed or stop altogether. As a result, after switching, the electric motor essentially starts again. That is, in the end, you will not only not achieve savings in engine life, but also, most likely, you will end up with excessive energy consumption.

Video: Connecting a three-phase asynchronous electric motor with a star or triangle

Electronic motor soft start system

A smooth start of the engine can be done using triacs connected to the control circuit. There are three schemes for such connection: single-phase, two-phase and three-phase. Each of them differs in its functionality and final cost, respectively.

With 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 service life of electric motors. Due to the fact that the engine starting is controlled by reducing the voltage, the rotor accelerates smoothly and not abruptly, as with other circuits.

In general, engine soft start systems are assigned several key tasks:

the main one is to reduce the starting current to three to four rated ones;
reducing the motor supply voltage, if appropriate power and wiring are available;
improvement of starting and braking parameters;
emergency network protection against current overloads.

Single-phase starting circuit

This circuit is designed to start electric motors with a power of no more than eleven kilowatts. This option is used if it is necessary to soften the shock at start-up, but braking, soft starting and reducing the starting current do not matter. Primarily due to the impossibility of organizing the latter in such a scheme. But due to the cheaper production of semiconductors, including triacs, they have been discontinued and are rarely seen;

Two-phase starting circuit

This circuit is designed to regulate and start motors with a power of up to two hundred and fifty watts. Such soft start systems sometimes equipped with a bypass contactor to reduce the cost of the device, however, this does not solve the problem of phase supply asymmetry, which can lead to overheating;

Three-phase starting circuit

This circuit is the most reliable and universal soft start system for electric motors. The maximum power of motors controlled by such a device is limited solely by the maximum temperature and electrical endurance of the triacs used. His versatility allows you to implement a lot of functions, such as: dynamic brake, flyback pickup or balancing of magnetic field and current limiting.

An important element of the last of the mentioned circuits is the bypass contactor, which was mentioned earlier. He allows you to ensure the correct thermal conditions of the electric motor soft start system, after the engine reaches normal operating speed, preventing it from overheating.

The soft start devices for electric motors that exist today, in addition to the above properties, are designed to work together with various controllers and automation systems. They have the ability to be activated by command from the operator or the global control system. Under such circumstances, when the loads are turned on, interference may appear that can lead to malfunctions in the automation, and therefore it is worth paying attention to protection systems. The use of soft start circuits can significantly reduce their influence.

Do-it-yourself soft start

Most of the systems listed above are actually not applicable in domestic conditions. Primarily for the reason that at home we extremely rarely use three-phase asynchronous motors. But there are more than enough commutator single-phase motors.

There are many schemes for smooth starting of engines. The choice of a specific one depends entirely on you, but in principle, having a certain knowledge of radio engineering, skillful hands and desire, it is quite you can assemble a decent homemade starter, which will extend the life of your power tools and household appliances for many years.