Since the early seventies of the last century, electric cutting tools from Bulgaria have been supplied to the territory of the USSR and other countries. He was different good quality and was popular, for which it received the short name “Bulgarian”.
Since then, it has been much clearer to Russian people than the technical term - angle grinder or angle grinder for short. Thanks to simple device and useful features, an angle grinder is necessary home handyman for renovating an apartment with your own hands.
We explain in this article how to choose it for your tasks, taking into account specific work.
Purpose
The grinder was originally created for grinding surfaces. But due to significant design upgrades, it quickly began to perform such useful functions as cutting and processing any building materials, including cement, concrete, brick, tiles, slate and all types of metals.
According to the methods of performing work, angle grinders, like all power tools, are designed for operation in one of two modes:
- constant work in construction conditions with overcoming maximum loads during a full work shift - professional models;
- for single use with the organization of breaks at rated loads - a household tool.
This is one of the important differences to consider when purchasing. It affects the cost of the grinder.
Professional models
To ensure that the tool works for a long time in extreme conditions and is at the same time convenient, manufacturers use all sorts of technical tricks. For example, an insulated copper wire not familiar to us round section, but in the shape of a square.
Even the plastic composition for the body is selected in such a way that when heated to 140 ° C it does not transfer high temperature to the operator’s hands and at the same time does not lose its strength.
Expensive models of grinders have:
- vibration-proof inserts on the handles that prevent the development of occupational diseases;
- quick-release nuts SDS, allowing you to install working parts without using a special wrench;
- rotating rear handle;
- gear rotation function or the ability to move the front handle to one of three positions;
- special bearing design that ensures balancing of the working body;
- long power cord with a protective layer of durable insulation;
- the ability to regulate the speed of the working circle and a number of other useful functions.
Household tool
Grinders of this class are inferior in their characteristics to professional tools. However, they are produced according to strict technical standards, meet safety standards, and allow work to be carried out while observing breaks.
Design and principle of operation
After connecting the power cord to the mains voltage and turning on the start button, the electric motor rotor begins to rotate. A gear transmission at its end transmits torque to the working circle.
When rotating under load, the disk material is subjected to significant loads and if the rules for handling it were violated during storage, it can break into pieces.
Automatic wheel balancing
Wear work surface does not always happen evenly. WITH outside Due to impacts and uneven loads, small potholes are formed, creating beating. This is most typical on large-diameter cutting wheels.
This function makes the operator’s work easier and allows him to do it better. The presence of auto-balancing indicates the prestige of the grinder model.
Protection against accidental activation
When the mains voltage is lost for various reasons and power is re-supplied to the angle grinder, an unplanned engine start occurs, which causes injury or equipment breakdown. Manufacturers prevented the occurrence of such an unpleasant situation by creating an appropriate block.
Motor protection against electrical overloads
To implement it, control is used by:
- current flowing in the motor circuit;
- winding temperature;
- or both of these options.
Such protection can only signal to the operator that the load has been exceeded by the light coming on or reduce the performance of the angle grinder by reducing the speed or completely stopping the engine.
Among workers who strive to quickly complete work under increased loads at any cost, this function causes irritation. But in general, it allows you to save the life of the tool and consumable wheels.
Motor overload protection in case of accidental jamming of the wheel
During a sharp stop of the wheel while the engine is running, a strong mechanical shock is transmitted to the latter, which is also felt as a sharp jerk from the operator’s hands. Different manufacturers use their own technical solutions for shock smoothing. Three variants are common technical solution, working on the basis of mechanics:
- safety slip clutch;
- centrifugal clutch;
- SJS spring design.
Slip clutch
The design includes several disks that engage the driven gear with the spindle. They provide adjustable torque transmission. When the nominal value is exceeded, the rotor continues to rotate and the working element stops.
The engine in this situation experiences a load, but it is less than during a jam.
Centrifugal clutch
The work is based on the transmission of torque due to petals, which provide traction from the action of centrifugal forces. Torque is transmitted to the working body when the rotor rotates and is removed when it stops.
SJS function
A coupling made using this original technology is used in Makita angle grinders. It prevents impact due to the spring pressing the small bevel gear. This smoothes out the shock, and at the same time reduces vibration, ensuring smooth operation of the working element.
In some expensive models of angle grinders, engine protection during overloads is carried out by removing voltage by a built-in electronic circuit.
Fixing the switch
This useful feature designed for using the tool with its stationary fastening in the holding mechanism and supplying the surface being processed to the working element. But we don’t recommend using it to remove your finger from the button and cut it conveniently.
If the disc gets stuck in the material being processed, it may fly apart and the grinder may jump out of your hands. The engine will run when the switch is locked. Try to stop him in this situation.
Dust protection
When cutting or grinding, a cloud of tiny particles of the material being processed forms around the wheel. It penetrates through the cracks of the housing, settles on the bearings, brushes, commutator motor, and changes the electrical resistance of the current-carrying circuits until a turn circuit is created. To combat dust install:
- fine mesh or filters on ventilation openings;
- armored stator windings and rotor cord bandage;
- closed type bearings;
- windings filled with epoxy resins;
- increased tightness housing.
Automatic brush shut-off
The function works on expensive models, it allows you to control the compression of the contact surfaces of the brushes to the rotor commutator plates, and preserve the service life of the engine.
To implement this, a spring-loaded dielectric pin is introduced into the brush design. It controls the degree of wear of the carbon electrode and, when the length is critically reduced by more than 2/3, presses the brush contact away from the commutator.
The self-switching mechanism of the brushes also works when an increased potential is supplied to the angle grinder in the event of a zero break, protecting the engine by breaking the current circuit.
Removing dust
Try to hammer a concrete slab indoors and you will immediately appreciate the cloud of dust that is generated during the work. A professional tool has a flange to which it is connected construction vacuum cleaner, which picks up debris directly from under the working element and takes it to the dust collector through a hose.
The function is very useful. But for performing single tasks around the house, such an angle grinder is quite expensive. However, you can purchase a special casing for these purposes.
The inner diameter has a built-in metal ring. It is the base for installation on the bushing and its surface ensures precise alignment relative to the axis of rotation due to four protruding teeth.
The side surface of the ring serves to hold it on the surface of the circle. It is not a basic surface that ensures pressing of the disk inside the flange, if only for the reason that the cutting wheel can have a thickness of 1 mm, and the recess in the flange and nut is about three.
The circle is pressed against the annular protrusion of the flange with its end surface due to the force of screwing the nut, and is held by the plane that creates the greatest moment of resistance - at the periphery.
On the side of the circle there is a picture with technical characteristics. The inner ring, like the picture, can be applied on both sides or on one. This marking is specified by the manufacturer not for installing the disk, but for other purposes. However, some workers mistakenly believe that it is a guide to the direction of rotation.
Where to direct the sparks
According to the laws of inertia, fragments fly from the rotating circle. Their high temperature can burn through clothing material and cause skin burns. If the circle gets stuck in the part being cut, it may fall apart into pieces that will fly in the same way. To protect the operator of the grinder, a metal casing is installed.
When working, the tool should always be positioned so that at any time an unusual situation arises protective cover ensured its function as much as possible - it protected the human body from sparks and fragments falling on it.
Checking the condition of the brushes
Service life
The service life of carbon electrodes as reliable current conductors is approximately 80÷120 hours of operation. After this period, wear occurs and they need to be replaced.
Signs of defect formation on contacts are:
- the appearance of sparks forming a circular beam on the collector;
- noticeable reduction in engine power;
- obvious depletion of the length of the carbon rods or the formation of chips on the surface of their contact.
Clamping force
Factory adjustment ensures optimal contact force between the brush and the commutator plates. If the brush assembly is worn out or incorrectly replaced, it may be damaged in the direction of increasing or decreasing contact.
Increased pressure
Excessive pressure from the hard brush is created on soft material collector plate, leading to excessive heating of engine parts.
Reduced pressure
Additional electrical resistance appears at the contacts, which does not ensure reliable current flow when switching the windings located on the rotor. A spark discharge appears that can develop into an arc that damages the brush assembly, commutator, and motor.
Therefore, when replacing brushes, it is necessary to control their force and use original spare parts from the manufacturer.
Our company offers power tools for construction and repair, consumables, related equipment and spare parts of the famous Japanese brand “Makita”. As an official dealer, we provide appropriate certificates for all tools sold. We sell only original spare parts for any Makita tool.
You can select the required part for the tool on this page. For successful registration application, you need to familiarize yourself with a few simple steps to prepare your order.
So, how to choose the right part correctly and quickly?
To go directly to selecting the required spare part or group of spare parts for a particular tool, you must go from the main page of the site to the hyperlink “MAKITA SPARE PARTS”, which is located in the upper right corner of the main page of the site. If this step is successfully completed, you will be taken to the “Makita spare parts” page.
Now we can see all the Makita tools grouped by type and schematically depicted. We select the group whose power tool requires repair and replacement of spare parts. You can use vertical scrolling. For example, select “Drills and saws”.
The “Drills and Saws” page contains the entire list of models for which you can order parts. We carefully select from the list of models provided by the site and activate the model you need by clicking the left mouse button. Let's choose one. For example, Makita 6310.
So, after selecting a specific model (in our case, Makita 6310), a page () will appear in front of you, which shows the assembly drawing of the selected model. Here you can print it on a printer (see Print a drawing). On the right side of the table there is a list of positions, names and quantities of parts in the tool. Each detail of the drawing is interconnected with its position in the list. When selected (by hovering the Mouse pointer over a part), the arrow changes to a hand, which allows you to click the left mouse button to mark the specified part in red. At the same time, the position of the same name in the list is marked in blue, and an application table appears at the bottom of the page. Moreover, it is worth paying attention to the fact that with the mouse you can select both a part in the drawing and its position in the table. The table below appears only when at least one part is selected. Next you need to decide what to do. There are several options under the generated application. You can cancel everything (reset everything) and start the selection again. You can continue the selection in other models (in this case, the order already made will also be displayed on the monitor), or you can go to the order form by clicking the appropriate link.
Notes: Directly in the application (in the table with the selected parts), you can use the arrows in the last column to enter the number of parts you need.
Please note: the minimum order amount is 1000 rubles
Having finally completed the Application, you can proceed to the order form, where you will be asked to fill out three information fields. Contact person (how to contact you), number mobile phone and work or home telephone numbers. After submitting your order for execution, wait for a call from the manager.
The company's employees - experienced professionals - will process the received order and within a day will inform you about the presence or absence of certain parts, their quantity, the price of the part and the total cost of the entire order. If any spare part is missing, you will be informed about the time it will be received from the manufacturer and, by agreement with you, may notify you about this again.
Typically, the order execution time does not exceed three working days. You can learn more about the delivery of goods by visiting the “Delivery” page.
The practice of this service shows that clients are using it more and more often. You receive the tool itself, consumables, and spare parts for them without leaving your apartment. You can discuss all complaints and wishes with the manager or delivery specialist.
As you know, nothing lasts forever and even tools from branded manufacturers break, not to mention the so-called “consumer goods”. And grinder (angular grinding machine) is no exception. By the way, angle grinders began to be called “grinder” during the Soviet Union, because at that time this tool was produced in Bulgaria and the first models were supplied from there. The grinder, as a tool, has become very widespread due to its versatility and ease of use. There are also many varieties and models of grinders, but the operating principle and design are not fundamentally different. Therefore, having considered the device of the instrument, possible malfunctions and repair methods, they can be applied to any model of angle grinder.
The device of the grinder relatively simple. The basis of the tool is its body, inside which there is an electric motor, a starting device and a gear transmission to the spindle, onto which various attachments are attached.
The body is made of strong impact-resistant plastic. Depending on the power, there are different dimensions and shapes of the tool. Some models have a regulator angular velocity, which is intended for optimal choice rpm, at various types work.
Another component could be a gearbox. The gearbox is designed to create optimal conditions transmission of rotation from the electric motor rotor to the cutting or grinding wheel. In this case, the number of revolutions on the output shaft of the gearbox decreases. Correctly selected rotation speed and circle diameter are the key to maximum efficient work tool.
A button for replacing the working disk, when pressed, locks the disk in a certain position, preventing it from spinning when removed.
The safety clutch serves as a limiter in case of sudden reactive torque. Otherwise, when the disc gets jammed in the material, the grinder itself begins to rotate sharply, which can lead to injury to the worker. This clutch does not allow such rotation.
An electric motor typically consists of a stator and a rotor. The stator is located in the guide bosses of the plastic body of the angle grinder. WITH back side The stator has a special device called a brush mechanism. It contains copper-graphite brushes. Brushes are necessary to transmit voltage to the rotor through the commutator assembly.
The rotor is located inside the stator and is fixed in the housing in bearing units, which are inserted directly into the tool body. The front bearing assembly is usually made in metal plate, or, this plate can be made of aluminum alloy.
The grinder gear housing is almost always made of aluminum alloy and has several threaded holes for attaching an additional handle. By screwing the handle into various holes, you can change the plane of location during operation.
The gearbox consists of two gears, with the help of which the direction of the output shaft changes by 90 degrees and the rotation speed is reduced. The ratio of the number of teeth of the primary gear to the number of teeth of the secondary gear is called the gear ratio.
Typical malfunctions of angle grinders and methods of diagnosis and repair
The grinder suddenly stopped working.
The first thing you need to do is physically disconnect from the network and manually turn the disc. If the disk does not spin or spins very slowly, immediately disassemble the tool for visual inspection. If it spins easily, then the most likely thing is that electricity is not reaching the brushes of the electric motor. That is, the problem lies either in the power plug, or in the wire itself, or in the “Start” button mechanism. It is enough to disassemble the case and “ring” the cable with a conventional tester, or in some other way, to check for a break. After repairing the break or replacing the wire, the angle grinder will start working.
The wire and plug are guaranteed to be intact, but the tool still does not work.
It is necessary to disassemble the trigger mechanism, and it is advisable to mark the contacts to be removed - if they are subsequently connected incorrectly, the winding may burn out or the armature may jam. Repairing the starting mechanism is not often possible - it is easier and more reliable to replace the starting button with any similar one with suitable power parameters. Such a button is not that expensive and you can buy it in any store of the appropriate profile.
The start button and power cord are in working condition, the grinder does not work.
Check brushes and brush holders. The brushes may be broken or completely worn out. The lifespan of these devices is usually limited to several years; of course, it all depends on the intensity of use. Repair the break or replace the brushes.
Then there are more serious faults, and therefore repairs require certain knowledge and skills.
Breakage or licking of gear teeth of the gearbox;
- jamming of bearings;
- failure of the armature or stator;
- failure of control electronics;
- failure of the collector;
- deformation of the body;
When determining mechanical defects in an angle grinder, more attention should be paid to the condition of the gear (large gear), shank (gear on the shaft) and bushings. Uneven wear of the teeth or shaky shafts indicates immediate replacement of the worn parts.
Breaking out the spindle lock button.
The reason is just one careless movement, namely pressing (intentionally or accidentally) a button while the disk is spinning. Sometimes breakdowns occur due to attempts to remove a jammed disk using a button. Many angle grinders have slots on the spindle where the disk is attached specifically for a regular open-end wrench, check your grinder, most likely you have one too. So, it’s better to use them and an open-end wrench than the disk lock button.
Chipped gear teeth.
Usually they occur due to jamming (in such a situation, tool breakage is not the worst thing that can happen). A sign of a malfunction is a rattling sound in the gearbox. If the gear has lost two or three teeth, then the tool will not be able to cut.
In this case, it is necessary to change the gears in pairs and the gear itself and the bevel wheel. When you go to the store for gears, don’t forget to write down the name of your grinder and its power.
Failure of the electric motor.
This often happens with tools that work in dust and are forced to rest in sand or on the ground: the sucked dust wears down the winding. However, you can destroy the motor without dust - by strong overloads, especially if the tool is low-power. Therefore, in small angle grinders, not only the armature, but also the stator often burns out. In small angle grinders, the electronic speed control unit also breaks down. If you use an angle grinder to cut highly dusty materials, in particular slate, putting a stocking over the ventilation slots in the body helps to protect the tool.
Bearings.
Another sore spot for grinders (as well as other rotating power tools). Few machines have strong immunity against dust, but high frequency rotation implies rapid wear. In general, bearings are not the worst failure; they are easy to change. However, it is important to replace it on time, otherwise there is a high probability of a more serious breakdown, the repair of which is comparable to the purchase
Stator
If, when turned on, the disk begins to gain speed and accelerates too much, there is definitely a turn short on the stator winding. Stator repair is one of the most serious damages and requires appropriate skills. If you are not confident in your abilities, then it is better to entrust this to professionals or use the services of a repair shop.
We begin the repair of the angle grinder stator by cutting off the frontal parts of the winding, the remains of which are removed. Next, we make a new winding using a template sandwiched between two large plates on an axis that can be inserted into an electric drill. The main thing is to achieve an identical number of turns made with the proper density and maintain the thickness of the wire. We insert two coils into the stator housing, the conclusions are made from the same winding wire, insulated with flexible tubes of the appropriate diameter.
Gearbox
Models with power up to 1100 W usually use spur gears mounted on the armature, but angle grinders with higher power, for example, 1500 W, require helical gears. Both options have a conical shape, since the axis of the gearbox rod intersects with the armature shaft, and transmission is possible only by angular engagement of the teeth.
As a rule, repairing an angle grinder gearbox consists only of replacing gears. If a disc gear is broken, it will be very difficult to remove it for replacement; this unit is best secured in the gearbox.
Speed controller
Almost all modern models of drills, jigsaws, and screwdrivers have a speed regulator. But not all grinders (grinders) are equipped with such a mechanism. In principle, a regulator is not needed for cutting metal with a cutting stone, but for grinding it is simply not replaceable. The proposed homemade regulator circuit is very simple and reliable. There are not many parts and they are not expensive. If you already have an angle grinder without a standard speed controller, then you can easily improve it.
You can also assemble it separately in a box with a socket and use it as a carrier with a power regulator. Or you can immediately assemble the regulator in the body of the angle grinder and remove the resistor handle.
Rules for using an angle grinder and preventive maintenance
The power tool should not be allowed to operate for a long time under load at a significantly reduced speed (this can be determined by ear) compared to the speed idle speed, and even more so, you should not allow the tool to be pinched (blocked), otherwise it will burn out within a few seconds.
After working at reduced speed, do not immediately turn off the power tool. To prevent local overheating, it needs to work for some time (more than 1 minute).
It is important to strictly follow the terms for replacing (adding) lubricant and its quantity specified in the operating instructions.
If the noise increases during operation of the angle grinder or if its performance characteristics deteriorate, it is necessary to carry out a professional examination. service.
Prevention consists of completely or partially disassembling the tool, cleaning, lubricating and replacing (if necessary) some parts.
Timely replacement of relatively cheap parts that wear out quickly will allow you to preserve more expensive long-term components, which will ultimately lead to savings in the operation of the tool, eliminate premature repairs and greatly extend the service life of the tool.
An angle grinder, which received the nickname “Bulgarian” in the post-Soviet space, was something every owner wanted to have in his home workshop 3-4 decades ago. Then for most people it really was a dream, since only one plant produced this electric tool - Eltos-Bulgarka in the Bulgarian city of Plovdiv (hence the popular name). And although over the past time the number and range of grinders have grown incredibly, the main components of the tool’s design have not changed.
Grinders are used not only for grinding and polishing surfaces, but also for processing metal and concrete (using diamond or abrasive wheels).
Electrical equipment for an angle grinder
Over 40 years, the appearance of the angle grinder has remained virtually unchanged: an oblong body with a motor and gearbox mounted inside, a handle screwed to the side and a protective casing.
A grinder, like any tool, sooner or later refuses to work. But there are situations when a simple repair of electrical equipment is sufficient to eliminate a malfunction. To complete this minor repairs, you need to have an idea of how such equipment works internally and be able to read its electrical diagram.
Electrical diagram grinder consists of the following elements:
- anchor;
- collector;
- electric brushes;
- gearbox;
- stator;
- handle holders;
- power cable with plug.
Each of these elements performs electrical circuit their functions, the malfunction of each leads to a stop in the operation of the tool. For example, the armature, being a rotating element of the chain, is responsible for the rotation of the grinding disc. To make the disk rotate, the armature must spin at an even higher speed. Therefore, the higher the rotation speed of the armature, the greater the power of the tool.
The collector is the area on the anchor where all the power and control cables exit. Its task is to translate the signals passing through the windings into a language understandable to the engine and control unit. If you remove the case cover, its polished plates immediately catch your eye, especially since they are relatively large in size.
The purpose of electric brushes is to provide current supply to the commutator from power cable. If they are in normal working condition, then after vent their even glow will be visible. If the glow is not noticeable or it pulsates, then this is a sign that there are problems with the brushes.
The gearbox is a very important part not only of the electrical circuit, but also of the entire design of the angle grinder. Its purpose is to supply energy from the rotating armature to the grinding disc, thus ensuring its rotation. In fact, it is the gearbox that is responsible for the speed and power of rotation of the grinding disc of the grinder.
The stator is the most technically complex component in the electrical circuit of an angle grinder. All the windings of the armature and rotor are pressed into it, determining their rotation. The coil windings located in the stator are designed up to the last turn. If the stator fails, successfully rewinding it by a non-professional is a very rare case. Therefore, if the stator in an angle grinder breaks down, it is better not to risk it and have it repaired in a workshop.
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Reading an Electrical Diagram
But knowing the purpose of the main elements of the instrument’s electrical circuit is not enough; you also need to be able to read this circuit. And although the electrical circuit of an angle grinder is not the most complex that you can come across among electrical circuits, even it can be difficult for a person far from electricity to understand without outside help.
The grinder circuit is designed like this: two stator windings are connected in series via a cable to a network with a voltage of 220 V and are not electrically connected to each other. They are turned on/off using a switch mechanically connected to the start button of the angle grinder. Each winding is connected through a contact to a graphite brush.
Then the electrical circuit, through two windings connected in parallel to graphite brushes, goes to the rotor, where it closes at the contacts of its commutator. It is noteworthy that the armature winding consists of many windings, but only two are directly connected to the graphite brushes. In 9 cases out of 10, the failure of a grinding machine, like any power tool, occurs due to a break in the electrical circuit.
To diagnose a circuit and detect faults in it, use special device- multimeter. This portable tester is useful not only for diagnosing an angle grinder, but also any other power tool, including electrical wiring in the house.
Testing should always begin at the electrical current input site and sequentially test all elements of the electrical circuit with a multimeter. To check the conductivity of electricity, the multimeter should be set to the minimum resistance position.
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Troubleshooting minor problems
If the grinder does not start when you press the “Start” button, it is quite possible that the cause of the breakdown is not too serious and the machine can be repaired on your own. There is a rule for repairing any power tool - move from simple to complex.
In the above situation, in 9 cases out of 10, the cause of the malfunction will be a break in the electrical circuit in the area from the power source to the graphite brushes. The first step is to remove the casing and check with a tester whether electricity is supplied to the “Start” button. If electric current does not reach the button terminals, then it is enough to change the old one electrical wire to a new one to repair the instrument.
If current flows to the trigger, but does not go further, then the problem is in the start button itself. It needs to be replaced, but this should be done slowly. First you need to carefully disassemble the trigger mechanism, and do not be too lazy to mark the contacts to be removed. To replace a button that has become unusable, any button that is suitable in size and with similar parameters will do. You need to be especially careful when reconnecting the contacts, since they incorrect installation will probably result in a burnt winding or a jammed armature.
If both the electrical wire and the start button are in full working order, but current does not flow to the graphite brushes, you first need to clean the contact plates of the brush holders attached to the commutator. If, even after performing this procedure, the grinder does not turn on, then the brushes themselves should be changed.
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Angle grinder Mastermax MCP – 2800
Angle grinder device
The angle grinder in our household use is necessary power tools. Depending on the installation of one or another attachment on the grinder, you can perform a varied amount of work.
In my own way appearance and designs similar to grinders are so-called grinders, consisting of such parts as:
- protective casing;
- ventilation hole;
- push-button switch;
- side handle;
- spindle lock.
The photograph shows the engagement mechanism, or in other words, the coupling of the mechanical part of the gearbox with the electric motor.
Grinder gearbox and electric motor
For the mechanical part, the following are subject to wear:
- bearings;
- reducer gears.
I would believe that giving a complete explanation of the mechanical part of the gearbox simply does not make sense.
Attachments for angle grinders have a different range, depending also on the work being carried out.
Electrical diagram - angle grinder
Let us concentrate our attention \Fig. 2\ on the following schematic representation - the principle of operation of the electric motor.
The red arrow in the figure shows the direction of the current, as is commonly believed in the section on electrical engineering: “Current in an electrical circuit flows from a source \clamp\ with a positive potential to a source with a negative potential. Moreover, the positive potential changes its sign to the opposite - from the resistance that has a connection in the electrical circuit.
The electrical circuit here is closed on the collector, or more precisely on the contact connections “winding - collector” \for the electric motor rotor\.
That is, the rotor commutator through the graphite brushes in the circuit has electrical connection.
The two stator windings of the electric motor are connected in series in the electrical circuit.
In my practice, a similar electrical connection \Fig. 2\ for all elements of a commutator electric motor - I have not seen a wire with one potential have a direct electrical connection to the commutator through a graphite brush, and a second wire with a different potential have a series connection through two stator windings with a second graphite brush.
The simplest and most complete explanation for these electrical connections is given directly by the electrical circuit of the commutator motor itself \Fig. 3\. It is this connection of all elements that is typical for grinder engines, where the electrical circuit is closed on two rotor windings - in this way.
Connection of electric motor windings
Here we can notice that the two windings of the electric motor rotor for this section are connected to each other in series and have a contact electrical connection “commutator - brush”.
The connection of the two rotor windings relative to the external alternating voltage source is parallel.
Among the causes of malfunctions of the electric motor of a grinder, one can cite such a malfunction as wear of the graphite brushes that are in contact friction with the electric motor commutator.
This part, like other other parts for power tools, can be purchased at specialized technical departments shops.
Electric motor diagnostics — grinders
Diagnostics of the electric motor of the grinder \Fig. 3\ should be carried out for individual areas electrical circuit of this circuit.
To do this, you will need either an ohmmeter or a multimeter. The Multimeter device is preliminarily for measuring resistance - it is set in the appropriate position.
To measure the resistance of two separate stator windings, one probe of the device is connected to the brush contact, the other probe of the device is connected to the corresponding pin electrical plug.
If this section breaks, the device will accordingly indicate the absence of resistance.
If it is working properly, the device will indicate the presence of resistance in one or another measured section of the electrical circuit.
By connecting the two probes of the device to the two pins of the electrical plug of the grinder, the display of the device will show the total resistance for:
- two stator windings;
- two rotor windings,
- that is, it will indicate the total resistance value.
Changing the rotation speed of the electric motor rotor \Fig. 4\ is carried out through the following electrical circuit.
The electrical circuit consists of:
- resistor R1 \0.5 W\;
- resistor R2;
- resistor R3 \5 W\;
- diode VD1;
- triode thyristor VS1.
Resistor R2 acts as a potentiometer, due to which the current in the load changes. The load in this explanation is the electric motor.
Triode thyristor - creates current blocking for the reverse direction. Control is carried out via the cathode.
Well, we figured out the simple ones electrical diagrams. All that remains is to make your decision in cases of malfunction - to send the electric motor for repair or to repair it yourself.
Let's go to a repair shop household appliances, - you can already state the reason for the malfunction of your power tool.
That seems to be all.