Disadvantages of power tools and service life
It is well known that not every tool is equipped with such soft start circuits. They mainly come in expensive models from well-known brands Bosch, Hilti, and DeWalt. Moreover, both in the network line and in the battery one.
A power tool without such a device has a bunch of disadvantages:
armature sparking on the commutator with armature lamellas burning out
brushes burn out and wear out faster
rotor and stator windings fail more often
current surge into the general electrical network
gears hitting each other and operating faster
dangerous jerk when starting, tearing the tool out of your hands and increasing the risk of injury
When working with a miter saw with a PP, the blade will not stray from the prepared cutting point
What is important for non-professional carpenters
If at your dacha or in your house at the initial stage of construction there is no electricity yet and you use a generator, then sooner or later you will understand that without a soft start unit (soft start unit) with sharp initial currents, the generator will not last long. Therefore, such a thing can save not only the tool, but also emergency power supplies.
You can, of course, independently build a BPP into the inside of the same grinder or trimmer, but not everyone wants to disassemble the equipment and tinker with the insides.
Plus, opening a new case will void the warranty. Therefore, the best use for the KRRQD12A unit is external connection.
Just keep in mind that it is suitable for commutator motors. For asynchronous ones, a frequency generator with different regulation principles is needed.
This box is designed for a current of 12 Amps.
There is also a more powerful 20A model.
What is typical is that they have the same dimensions, but the difference in price is a couple of tens of rubles.
It would seem better to take it, but for a standard 16A socket the first option is more profitable. There will be no desire to connect a more powerful load and thereby burn all the contacts.
DIY craftsmen, of course, assemble similar circuits with their own hands, based on VTA 12-600 or other thyristors, capacitors, a dinistor and a couple of small resistors. You can find many examples of schemes on the Internet.
Soft starters with three wires
By the way, be careful, there are similar devices, but with three wires. For example XS-12/D3.
Or other models that look similar to KRRQD.
But they are assembled on a slightly different principle and need to be installed after the START button, in the instrument itself. Voltage should be applied to them only at the moment the grinder's start button is closed and immediately disappear after it is released.
The connection diagram for them is as follows:
The phase is supplied to contact “A”, zero to “C”. Next, the phase with the output control wire goes to the engine (this is exactly the third wire).
Without a button, such a device will be constantly powered by 220V, which is not acceptable.
There is no such thing in a two-wire unit, since it is connected to an open circuit, and voltage (potential difference) is applied to it only at the moment of starting and operating the tool.
Another point is the so-called electric brake or brake winding on the crosscuts. It may not work with a 3-wire external soft starter, but it will work with a 2-wire model.
Frequent malfunctions, causes
The grinder may not gain the speed required by the regulatory regime, work with spontaneous changes, with jerks, and in extreme cases, stop rotating altogether. If there is a speed control option, it may not respond to changes in the position of the operating mode indicator.
Some types of malfunctions and methods for eliminating them are discussed in the presented videos.
Not gaining momentum
The Makita model grinder, powered by batteries, did not reach operating speed in the next video. The first reason that comes to mind is that the batteries are discharged, but this has not been confirmed. When disassembling the tool, faulty brush holders were discovered. The ingress of foreign oily liquid into the brush-collector assembly caused destruction of the brushes and melting of the plastic structure of the brush holders.
The author replaced the defective one with a new brush mounting unit.
Important: graphite dust from damaged brushes should be carefully removed from the stator and rotor, the surface of the commutator should be cleaned with emery cloth and preferably polished
Does not develop speed and smokes
The stability of the rotation speed of the spindle working shaft largely depends on the presence of malfunctions in the components of the electrical part of the angle grinder. In the next video, the stator winding burned out, resulting in smoke and the grinder stopped rotating. Stator failure can be easily determined visually: broken wires, burnt insulation.
The author had a used, but fully functional stator in stock, so he eliminated the defect by replacing the failed one.
It's getting warm
Poor contact in the connections of the electrical part of the angle grinders leads to strong heating of the body, the formation of increased spark strength due to deviations from the nominal values of the electrical parameters. In the next video, the contacts on the brush holders burned out. Perhaps this happened due to a violation of the location of the brushes, which led to a large formation of graphite dust and the creation of additional resistance on the commutator unit. The author suggested a more reliable connection of contacts and corrected the location of the guides for the brushes.
Loses speed under load
In the next video, the grinder spontaneously changed speed during operation, and from time to time there were jerks. At the same time, there was no option for adjusting the speed on the angle grinder. One such jerk caused the cutting disc to break. After which it was decided to find and fix the problem. Diagnostics of the electrical part when testing with a multimeter revealed that the power (start) button was faulty.
Since such buttons are usually not suitable for repair (when disassembling it, a completely defective contact was discovered), the author found a replacement. Functionally, the new button duplicated the old one, but was slightly different in size. The author successfully chose a new location for it and the grinder restored its functionality.
How to make a starter unit for a power tool
There are quite a lot of options for independently equipping an angle grinder with a soft start device. Some of them are presented in the author's videos.
Starter unit based on LM358 chip
In the following video, the author shares his experience of independently manufacturing a soft-starter board according to a diagram taken from the Internet, based on the LM358 chip. The author made the housing for the board from a shampoo box, which speaks of the rich imagination of amateur craftsmen. The author did not just blindly copy the circuit from the Internet, but modified it by replacing the characteristics of some of its elements: transistors, diodes, resistors. The radiator for cooling semiconductor devices is taken from a tape recorder. In order to be able to place the soft start unit inside the body of the angle grinder, and not as in the case of the proposed option, a smaller board was developed.
Technology of work on the manufacture of the starting unit
The author of the following video describes in detail the work methods, components used and auxiliary technological materials for the manufacture of a soft starter. Here the K1182 microcircuit is taken as the basic element. The technology is not designed for use as the basis of a printed circuit board; the author calls such an assembly “surround mounting” technology. In this type of work, in addition to soldering, individual elements are fastened using fasteners, for example, this is how a triac is attached to a heat sink. The ready-made launcher is not universal for all angle grinders. On two angle grinders taken separately by the author, they reached the operating mode in significantly different periods of time.
One of the layout options for a homemade launch unit
As the initial option, the author of the following video chose a well-known assembly with the LM358 chip on the Internet. Since the assembled starting unit did not fit inside the body of the angle grinder, the author “packed” only a triac with a radiator inside, due to good cooling conditions from the angle grinder’s fan wheel. The rest of the block, together with the microcircuit, was secured to the body of the angle grinder.
Using an iron as an additional load to reduce the speed of an angle grinder
This method does not specifically relate to the topic of soft start of an angle grinder. However, to understand the principle of operation of an electronic device, the dimmer, which is used to adjust the power (or number of revolutions) of the angle grinder, is quite acceptable. In the next video, the iron takes a certain power from the angle grinder, thereby reducing its speed.
The typical starter circuit diagram should be modified for each individual power tool
The author of the following video tells how he equipped his household grinder with a soft start device to increase its service life.
Important: the circuit may work perfectly for adjusting the brightness of the lamp, but for the necessary functioning of the angle grinder, upon startup, be unable to perform the task. For effective operation, it should be “customized”, namely, select the required values of resistors, capacitors and possibly change the characteristics of semiconductor devices.. https://www.youtube.com/embed/-_-tAsrUyCM
How to install a standard dimmer in an angle grinder to adjust speed
In the next video, the author modified the power button (made it spring-loaded) in order to use the capabilities of a purchased dimmer to adjust the speed of the angle grinder. After turning on the angle grinder, moving the button sets the required speed mode. The dimmer fixes this mode and when turned on again, it is set.
Homemade options
There are many schemes for modernizing power tools using soft starters. Among all varieties, devices based on triacs are widely used. A triac is a semiconductor element that allows you to smoothly regulate power parameters. There are simple and complex circuits that differ in design options, as well as in the supported power of the connected power tool. The design includes internal ones, which allow them to be built inside the case, and external ones, manufactured in the form of a separate module, which acts as a speed limiter and starting current when starting the angle grinder directly.
The simplest scheme
A soft starter with speed control on a thyristor KU 202 is widely used due to its very simple design (diagram 1). Connecting it does not require any special skills. Radio elements for it are very easy to obtain. This regulator model consists of a diode bridge, a variable resistor (acts as a U regulator) and a thyristor tuning circuit (supplying U to the control output with a nominal value of 6.3 volts) from a domestic manufacturer.
Due to the size and number of parts, this type of regulator can be built into the body of a power tool. In addition, the variable resistor knob should be removed and the speed controller itself can be modified by integrating a button in front of the diode bridge.
The basic principle of operation is to regulate the speed of the electric motor of the tool by limiting the power in manual mode. This circuit allows you to use power tools with a power of up to 1.5 kW. To increase this indicator, it is necessary to replace the thyristor with a more powerful one (information about this can be found on the Internet or in a reference book). In addition, you need to take into account the fact that the thyristor control circuit will differ from the original one. KU 202 is an excellent thyristor, but its significant drawback is its configuration (selection of parts for the control circuit). To implement a soft start in automatic mode, scheme 2 is used (soft starter on a microcircuit).
Soft start on a chip
The best option for manufacturing a soft starter is a soft starter circuit with one triac and a microcircuit that controls the smooth opening of a pn type transition. The device is powered from a 220 V network and is easy to assemble yourself. A very simple and universal soft start circuit for an electric motor also allows you to regulate the speed (diagram 2). The triac can be replaced with the same one or with characteristics exceeding the original ones, according to the reference book of semiconductor-type radioelements.
Scheme 2. Scheme for soft start of a power tool
The device is implemented on the basis of the KR118PM1 microcircuit and a triac. Due to the versatility of the device, it can be used for any tool. It does not require configuration and is installed into the power cable.
When the electric motor starts, U is supplied to KR118PM1 and the charge of capacitor C2 gradually increases. The thyristor opens gradually with a delay depending on the capacitance of the control capacitor C2. With a capacitance of C2 = 47 μF, there is a delay at startup of about 2 seconds. It depends directly proportionally to the capacitance of the capacitor (with a larger capacitance, the startup time increases). When the angle grinder is turned off, capacitor C2 is discharged using resistor R2, the resistance of which is 68 k, and the discharge time is about 4 seconds.
To regulate the speed, you need to replace R1 with a variable resistor. When changing the parameter of the variable resistor, the power of the electric motor changes. R2 changes the amount of current flowing through the triac input. The triac needs cooling and, therefore, a fan can be built into the module housing.
Thus, to start electric motors of various tools, it is necessary to use factory-made or home-made soft starters. Soft starters are used to increase the service life of the tool. When starting the engine, there is a sharp increase in current consumption by 7 times. Because of this, the stator windings may burn out and the mechanical part may wear out. Soft starters can significantly reduce the starting current. When making a soft starter yourself, you need to follow safety rules when working with electricity.
Originally posted 2018-07-04 07:37:29.
How to make a soft start yourself
Due to the simplicity of the circuit, it is not difficult to assemble a soft start device for an electric motor using a triac. It is made from available parts. It is best to do it on a printed circuit board, so nothing will dangle and short out. The triac must be mounted on a heat sink made of aluminum. It is better if it is a factory radiator designed for a power of 10-30 W. Then it is suitable for power tools with a power of 1000-1200 W.
Calculating the radiator is very simple by calculating the current. The triac voltage drops about 1.5-2 volts when it is open. The current is obtained by dividing the power by the mains voltage. For example, a power tool rated at 1200 watts: 1200/220 = 5.45 amps. Multiply by 2, we get 11 W.
Usually, in a commercial power tool, the power limiting circuit is hidden somewhere in the handle or body of the angle grinder or drill. There is no way to place a normal radiator there. If it is started frequently, it overheats and does not perform its functions. Only a good professional power tool has a normal device for limiting the starting torque and adjusting the speed.
NOTE : It is best to make a soft start module for a power tool in a box with a socket. Do not use outlet boxes that are too small. It is difficult to place a normal radiator for a triac there. Without a radiator, the device will be of no practical use! When assembling the radiator with the device, it is necessary to ensure the cleanliness of the mating surfaces and a thin layer of heat-conducting paste (KTP-8 or an imported analogue).
The radiator must be mounted on the same board on which the other parts are assembled. The board is placed in a box of suitable dimensions and is quite durable. These boxes can be purchased from electrical supply stores or made from sheet plastic. A clean, empty glue or paint can with a screw-on or tight-fitting lid may work. It must be durable and unbreakable.
The socket installed in the device must be rated for the rated current of the electric motor used. It's a similar story with the power cord.
IMPORTANT! If the power tool is equipped with a speed controller, its handle must be securely insulated. The device is under mains voltage and may be a source of electric shock if the insulation is poor.
After installation, it is useful to coat the printed circuit board with nitro varnish to protect it from moisture. The schematic diagram and analysis of its operation are in the next section.
Soft start on the KR1182PM1 microcircuit
This is a microcircuit for Russian-made power tools, which is produced by CJSC “NTC SIT” (Bryansk). It can be purchased retail in many online stores. Also new name K1182MP1R.
Starters for angle grinders with a 20 A triac
Devices with 20 A triacs are suitable for professional grinders. Many models use contactor resistors. First of all, they are able to operate at high frequencies. The maximum temperature of the starters is 55 degrees. Most models have a well-protected case. The standard device circuit involves the use of three contactors with a capacity of 30 pF or more. Experts say that the devices stand out for their conductivity.
The minimum frequency for starters is 35 Hz. They are capable of operating in a DC network. Modifications are connected via adapters. Such devices are well suited for 200 W motors. Filters are quite often installed with triodes. Their sensitivity indicator is no more than 300 mV. Quite often there are wired comparators with a protection system. If we consider imported models, they have an integrated converter that is installed with insulators. Current conductivity is ensured at around 5 microns. With a resistance of 40 Ohms, the model is capable of stably maintaining high speeds.
The disadvantage of small cheap angle grinders is the lack of soft start and speed control. Anyone who has plugged in a powerful electrical appliance has noticed how the brightness of the network lighting drops at that moment. This is due to the fact that powerful electrical appliances consume enormous current at the moment of startup, and accordingly, the voltage in the network sags. The tool itself may fail, especially a Chinese one with unreliable windings.
The soft start system will protect both the network and the tool. There will also be no strong kickback (shock) at the moment of switching on. And the speed regulator will allow you to work for a long time without overloading the tool.
The presented circuit is copied from an industrial design, installed on expensive devices. It can be used not only for an angle grinder, but also for a drill, milling machine, etc., where there is a commutator motor. The circuit is not suitable for asynchronous motors; a frequency converter is required.
First, I drew a printed circuit board for the soft start system, without components for adjusting the speed. This was done on purpose, because... In any case, the regulator must be wired out. Having a diagram, everyone can figure out what to connect where.
In the circuit, the regulating element is a dual operational amplifier LM358, which controls the power triac BTA20-600 through transistor VD1. I didn't get it from the store and installed BTA28 (more powerful). For a tool up to 1 kW, any triac with a voltage of more than 600V and a current of 10-12A is suitable. Because Since the circuit has a soft start, the starting currents will not burn such a triac. During operation, the triac heats up and should be installed on a radiator.
The phenomenon of self-induction is known, which is observed when a circuit with an inductive load is opened. In our circuit, circuit R1-C1 dampens self-induction when the grinder is turned off and protects the triac from breakdown. R1 from 47 to 68 Ohm, power 1-2W. Film capacitor 400V.
Resistor R2 provides current limitation for the low voltage part of the control circuit. This part itself is both a load and, to some extent, a stabilizing link. Thanks to this, after the resistor it is possible not to stabilize the power supply. Although there is a variant of the same circuit with an additional zener diode. I didn't install it because... The supply voltage of the microcircuit is within normal limits.
Possible replacements for low-power transistors are indicated below the diagram.
The regulator is adjusted using multi-turn resistor R14, and the main adjustment is done using resistor R5. The circuit does not allow power adjustment from 0, but only from 30 to 100%. If you need a simpler, powerful regulator from 0, then you can assemble a version that has been proven over the years. True, for an angle grinder, obtaining the minimum power is pointless.
We check the functionality of the circuit by connecting a 220V light bulb with a power of 40-60W. If the brightness is adjustable, then after disconnecting from the network, we check the triac by touch for heat generation. It must remain cold. Next, we connect the board to the grinder and check the smooth start and speed control without load. If everything is in order, we move on to testing under load.
So a cheap grinder turned into a mid-level tool.
Components for assembly
- LM358 can be purchased here
- S9014 can be purchased here
- S9015 can be purchased here
- A set of resistors can be purchased here
- BTA20-600 can be purchased here
Do-it-yourself soft start diagram for an electric motor for an angle grinder
Everyone who has been using an angle grinder for more than one year has had it break. At first, each master 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 instrument remains lying on the shelf with burnt windings. And to replace it, a new grinder is bought.
Drills, screwdrivers, hammer drills, and milling cutters are necessarily equipped with a speed control. Some so-called calibration grinders are also equipped with a regulator, while ordinary 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 simplest angle grinder can be upgraded so that its gearbox and armature winding wires will no longer be damaged. These troubles mainly occur during a sharp, in other words, shock start of the angle grinder.
All modernization consists simply of assembling the electronic circuit and securing it in the box. In a separate box, because there is very little space in the handle of the sander.
The tested, working diagram is posted below. It was originally intended to regulate the intensity of lamps, that is, to operate on an active load. Her main advantage? simplicity.
- The highlight of the soft starter, the circuit diagram of which you see, is the K1182PM1R microcircuit. This microcircuit is highly specialized, domestically produced.
- The acceleration time can be increased by choosing a larger capacitor C3. While this capacitor is charging, the electric motor accelerates to maximum speed.
- There is no need to replace resistor R1 with a variable resistance. A 68 kOhm resistor is optimally selected for this circuit. With this setting, you can smoothly start the angle grinder with a power of 600 to 1500 W.
- If you are going to assemble a power regulator, then you need to replace resistor R1 with a variable resistance. A resistance of 100 kOhm or more does not reduce the output voltage. By short-circuiting the pins of the microcircuit, you can completely turn off the connected grinder.
- By inserting a VS1 semistor of type TS-122-25 into the power circuit, that is, 25A, you can smoothly start up almost any commercially available grinder with a power from 600 to 2700 W. And there remains a large reserve of power in case the grinder jams. To connect angle grinders with a power of up to 1500 W, imported semi-sectors BT139, BT140 are sufficient. These less powerful dongles are cheaper.
The semisistor in the above circuit does not open completely; it cuts off about 15V of the mains voltage. This voltage drop does not affect the operation of the grinder in any way. But when the semistor heats up, the speed of the connected instrument decreases greatly. This problem can be solved by installing a radiator.
This simple circuit has one more drawback - it is incompatible with the speed controller installed in the tool.
The assembled circuit must be hidden in a plastic box. A housing made of insulating material is important because you need to protect yourself from mains voltage. You can buy a junction box at an electrical supply 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 circuit diagram below is standard for the XS–12 module. This module is installed in the power tool during factory production.
If you need to change the speed of the connected electric motor, then the circuit becomes more complicated: a 100 kOhm trimmer and a 50 kOhm adjustment resistor are installed. Or you can simply and crudely introduce a 470 kOhm variable between the 47 kOhm resistor and the diode.
It is advisable to connect a 1 MΩ resistor in parallel with capacitor C2 (it is not shown in the diagram below).
The supply voltage of the LM358 microcircuit ranges from 5 to 35V. The voltage in the power circuit does not exceed 25V. Therefore, you can do without an additional zener diode DZ.
Whatever soft start circuit you assemble, never turn on the tool connected to it under load. Any soft start can be burned if you rush. Wait until the grinder unwinds, and then work.
Manufacturing a soft start socket
The most important requirement for such an outlet is its mobility. Therefore, you will need a carrier.
With its help, you can smoothly launch the tool anywhere - in the garage, at the dacha, during the construction of your house in different areas of the construction site.
The first step is to disassemble the carrier.
The main power wires in it can be either soldered or connected to screw terminals.
Depending on this, your additional outlet will also be connected. This should be an additional socket near the carrying case in order to be able to simultaneously connect the instrument in different modes.
By the way, if you mistakenly turn on an angle grinder or circular saw that has a factory built-in soft start into an outlet that is also equipped with such a soft starter, then surprisingly everything will work. The only thing is that there will be a delay in starting the saw or turning the disk for a couple of seconds, which is not very convenient to use and can be puzzling if you don’t get used to it.
Here are real tests of such a connection, carried out by one master from YouTube BaRmAgLoT777. His comment after such tests on a Dremel type engraver, a Bosch drill, a Makita router, and an Interskol circular saw:
Next, to assemble the socket, take a stranded copper wire with a cross-section of 2.5 mm2 and strip its ends.
Then you need to tin the contact pad on the carrier where this wire will be soldered.
Securely solder the cable cores to these pads.
Carefully lay out the wires and close the extension cord.
Take a square external socket for installation on the outer surface of the walls, and try on a soft starter unit in its housing. Since it has compact rectangular dimensions, it should fit there without any problems.
Mount and secure the socket body on the same platform as the extension cord.
The PP block is connected to the gap of any wire, phase or neutral. Do not confuse it, phase and zero are not supplied to it at the same time, i.e. 220V.
It is installed on one of the wires.
Also for this BPP, there is no difference on which side to make the entrance and on which side to make the exit. The twists are soldered and insulated with heat shrink.
After that, all the insides of the socket are assembled into a housing and all that remains is to close the entire structure with a lid.
At this point, the entire reworking of the carrying case and the manufacture of the socket can be considered complete. It will take you no more than 15 minutes.
Models for angle grinder 600 W
For 600 W angle grinders, starters with contact triacs are used, in which the overload does not exceed 10 A. It is also worth noting that there are many devices with plates. They are distinguished by their security and are not afraid of elevated temperatures. The minimum frequency for 600 W angle grinders is 30 Hz. In this case, the resistance depends on the installed triode. If it is used of the 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. Very rarely, models have stabilizers that operate from comparators. Most often they are attached directly to the modules. Some modifications are made with wired transistors. Their minimum frequency starts from 5 Hz. They are afraid of overloads, but are able to maintain high speeds at a voltage of 220 V.
Read also: Silicone insulated wire marking
Smooth start -
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Device diagram for an angle grinder with a 10 A triac
The do-it-yourself soft start circuit for an angle grinder involves the use of contact resistors. The polarity coefficient of modifications, as a rule, does not exceed 55%. Many models are produced with interlocks. A wired filter is responsible for protecting the device. Low frequency transceivers are used to pass 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. Covers for starters are suitable on a semiconductor basis. In some cases, magnetic transceivers are installed. They handle low speeds well and can maintain the rated frequency.
Why was a soft engine start needed?
So, the problem is that the boiler room has pumps for feeding the boiler with water. There are only two pumps, and they are turned on by command from the system for monitoring the water level in the boiler. Only one pump can operate at a time; the pump is selected by the boiler room operator by switching the water taps and electrical switches.
The pumps are driven by conventional asynchronous motors. 7.5 kW asynchronous motors are switched on through conventional contactors (magnetic starters). And since the power is high, the start-up is very hard. Every time you start, there is a noticeable water hammer. The engines themselves, the pumps, and the hydraulic system deteriorate. Sometimes it feels like the pipes and taps are about to shatter into pieces.
In addition, when the boiler has cooled down and hot water is suddenly supplied to it (more than 95 ° C), then unpleasant phenomena occur, reminiscent of explosive seething. It happens the other way around, water with a temperature of 100 °C can be cold - when there is dry steam in the boiler with a temperature of almost 200 °C. In this case, harmful water hammer also occurs.
There are two identical boilers in the boiler room, but the second one has frequency converters for pumps. Boilers (more precisely, steam generators) produce steam with a temperature of more than 115 ° C and a pressure of up to 14 kgf/cm2.
It is a pity that the design of the boiler in the electrical circuit did not provide for smooth activation of the pump motors. Although the boilers are Italian, it was decided to save money on this...
I repeat that to smoothly switch on asynchronous motors we have the following options to choose from:
- star-delta circuit
- smooth start system (soft start)
- frequency converter (inverter)
In this case, it was necessary to choose the option that would require minimal intervention in the operating boiler control circuit.
The fact is that any changes in the operation of the boiler must be agreed upon with the boiler manufacturer (or a certified organization) and with the supervisory organization. Therefore, changes must be made quietly and without unnecessary noise. Although, I don’t interfere with the security system, so it’s not so strict here.
My regular readers know that now, after passing the exams at Rostekhnadzor, I have every right to perform instrumentation and automation work in the boiler room.
Disadvantages of angle grinders without soft start
Cordless angle grinder Metabo W 18 LTX 125 602174850 with soft start. Photo VseInstruments.ru
In addition to providing comfortable working conditions for the user, the angle grinder with soft start has a number of other advantages.
- The absence of a large starting current during the soft start of the angle grinder, which is several times higher than the nominal value of this parameter during operation, increases the reliability of the electrical part of the power tool. In this case, the winding wires do not experience overloads and do not crack, the commutator lamellas and brushes are not subject to wear from increased sparking, and processes that worsen the connection do not occur at the contact points.
- During a uniform increase in the speed to the nominal value, the angle grinder with a soft start does not experience increased dynamic loads that arise in its absence. An instantaneous acceleration of 6000 rpm or more does not leave its mark on the gear transmission and bearing units. They fail faster, so angle grinders without such a device are more often repaired.
