The use of electrical circuits in the repair of grinders

The angle grinder, which received the nickname “Bulgarian” in the post-Soviet space, 3-4 years ago, every owner wanted to have in his home workshop. Then, for most people, it really was a dream, as this electric tool was produced by only one factory - “Eltos-Bulgark” in the Bulgarian city of Plovdiv (hence the popular name). And although over the past time the number and range of Bulgarians grew incredibly, the main components of the tool design have not changed.


The grinder is used not only for grinding and polishing surfaces, but also for processing metal and concrete (with the help of diamond or abrasive wheels).

Device of the electric equipment of the Bulgarian

For 40 years, the appearance of the grinder has not changed: an oblong body with an inboard engine and gearbox, a screwed handle and protective casing on the side.

The Bulgarian, as well as any tool, sooner or later refuses to work. But there are situations when the simplest repair of electrical equipment is enough to eliminate a malfunction. To perform this minor repair, you need to have a concept of how such equipment works inside, and be able to read its electrical circuit.

The electrical circuit of the grinding machine consists of the following elements:

Wiring diagram grinders

Wiring diagram grinders.

  • anchor;
  • collector;
  • electrical brushes;
  • gearbox;
  • stator;
  • handles;
  • power cable with plug.

Each of these elements performs its functions in the electrical circuit, the failure of each leads to stopping the operation of the tool. For example, the anchor, being a rotating element of the chain, is responsible for the rotation of the grinding disc. To make the disc rotate, the anchor must spin at an even higher speed. Therefore, the greater the rotation speed of the armature, the greater the power of the tool.

The collector is an anchorage area, to which all power and control cables go. 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 cover of the case, then its polished plates immediately catch the eye, especially since they have relatively large sizes.

Causes malfunctions grinders

The reasons for the malfunction of the grinder.

The purpose of electrical brushes is to provide current to the collector from the power cable. If they are in normal working condition, then through the vent will be seen their even glow. If the glow is imperceptible or it pulsates, then this is a sign that there are problems with brushes.

The gearbox is a very important detail not only of the electrical circuit, but also of the entire construction of the 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 node in the electrical circuit of the grinder. All windings of the armature and rotor, determining their rotation, are pressed into it. The coil windings located in the stator are rated to the last turn. When a stator fails, rewinding is successfully performed by a non-professional - a very rare case. Therefore, if the stator has broken in the Bulgarian, then it is better not to risk it and eliminate its malfunction in the workshop.

Back to table of contents

Reading electrical circuit

But to know the purpose of the basic elements of the electrical circuit of the tool is not enough, you still need to know how to read this circuit. And although the electrical circuit of a Bulgarian is not the most difficult thing that you can meet from electrical circuits, but even a person who is far from electricity can find it out without outside help.

The device is an ordinary grinder

The device is an ordinary grinder.

The Bulgarian circuit is designed as follows: two stator windings are connected in series through a cable to a network with a voltage of 220 V and are not electrically interconnected. Their on / off is carried out using a switch, mechanically connected with the start button of the grinder. Each winding is connected through a contact with a graphite brush.

Further, the electric circuit by two windings connected in parallel to the graphite brushes goes to the rotor, where it closes at the contacts of its collector. It is noteworthy that the anchor winding is a set of windings, but only two are connected directly to the graphite brushes. In 9 out of 10 cases, the failure of a grinding machine, like any other power tool, happens due to an open circuit in the electric circuit.

To diagnose the circuit and detect faults in it, use a special device - a multimeter. This portable tester is useful not only for diagnostics of the Bulgarian, but also any other electric tool, up to an electrical wiring in the house.

Testing should always begin at the site of input of electric current and consistently ring out 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.

Back to table of contents

Minor troubleshooting

If the Bulgarian does not start when you click on the "Start" button, it is quite possible that the cause of the breakdown is not too serious and the machine can be repaired on its own. There is a rule to repair any power tools - move from simple to complex.

The device anchors grinders

The device anchors grinders.

In the above situation, in 9 out of 10 cases, the cause of the malfunction will be an open circuit in the area from the power source to the graphite brushes. The first thing you need to remove the casing and check with a tester, if electricity is supplied to the "Start" button. If the electric current is not supplied to the button terminals, it is enough to change the old electric wire to a new one in order to repair the tool.

If the current arrives at the trigger but does not go further, then the problem is in the start button itself. It must be replaced, but it should be done slowly. First, you need to carefully disassemble the trigger, while not be lazy to mark the contacts to be removed. To replace a button that has become unusable, any one that fits in size and with similar parameters will be suitable. You should be especially careful when re-connecting the contacts, since their incorrect installation will most likely turn into a burnt winding or a wedged anchor.

If both the electric wire and the start button are in good condition, but the current does not flow to the graphite brushes, you need to first clean the contact plates of the brush holders attached to the collector. If, however, after performing this procedure, the grinder does not turn on, then the brushes themselves should be changed.

Back to table of contents

Replacing graphite brushes

Practice shows that it is graphite brushes most often become the cause of the malfunction of the grinder. Their service life is limited to 1.5-2 years. Replacing old brushes with new ones will not be difficult. To check the brushes, the housing must be open. Getting to them is easy. First you need (with the cord disconnected from the socket) with a straight screwdriver, carefully lift and move the brush holders attached to the collector to the side. Screwdriver can be used to remove the brushes. If you have a corporate tool, then most likely the brush is held by means of a spring, and to remove it, it is enough to press this spring with a screwdriver. If the tool is Chinese, then there are plugs in it, which will have to be removed with a screwdriver, only after that you can remove the brush.

Brushes need only be changed to new ones purchased in a specialty store. When buying them, be sure to take the brush out with you and measure the purchase to fit the size. Insert a new brush into the brush holder, be sure to check if it runs smoothly.

If it never clings anywhere, then you can fix the brush in the brush holder. Then drown it inside and you can put the brush holder in the landing slot. Similarly, replace the second brush. Finally, check how carefully and correctly you laid the wires, whether they will not be clamped anywhere. After that, you can close the case and try to turn on the machine.

Replacing brushes is the maximum that common sense allows for self-repair in the grinder, without risking due to inexperience or inability to spoil the tool.

More complex repairs, such as cleaning the collector, replacing the gearbox or anchor, without having the necessary experience, it is better not to do it yourself. If the need arises - invite a friend who has already performed similar repairs on several occasions. You can do the repairs yourself with your own hands, but only under his supervision and by prompts.

Better yet, take your instrument to the workshop. Yet the Bulgarian, even fully serviceable, remains a source of increased danger. It is better to pay professionals for repairs than to pay doctors for their treatment.

Add a comment