Angle grinder sparks in the area of the brushes cause
The company "BAU-Rent" offers to get acquainted with the main malfunctions of grinders (angle grinder): why it does not work, it gets hot, sparks, vibrates, makes noise and does not gain momentum.
Why won’t the angle grinder turn on?
Most of the problems with an angle grinder are electrical. The instrument may not turn on for the following reasons:
- Damaged cable or defective plug;
- The start button is out of order;
- Severe wear of the brushes or lack of contact between them and the cable;
- Failure of the rotor or stator windings is the most serious reason why the "angle grinder" does not start.
It is advisable to solve problems with an electric motor in a specialized workshop, in which qualified specialists work and have modern diagnostic equipment and repair tools.
Why is the "angle grinder" not picking up the required speed?
- Faulty cable – due to mechanical damage or kinks.
- Breakdown of the control unit. To check if the angle grinder needs repair of the speed governors, turn it on directly: if the "angle grinder" works, then the problem lies in the adjusting block.
- Collector dustiness. Cleaning is carried out with alcohol solutions.
- Brush problems.
Why does the "angle grinder" spark strongly in the area of the brushes?
During normal operation, there is a slight uniform sparking inside the case. If it is too strong, the brushes must be replaced. The problem occurs in the following situations:
- Damage to the armature winding – an interturn short circuit has occurred or the winding section has broken.
- Lost contact between the winding and the collector plates.
- Breach of isolation between the collector lamellas.
- Badly worn bearings "angle grinder", which provoke the beating of the armature of the angle grinder, due to which the brushes sparkle and burn strongly.
- Using brushes, whose characteristics do not correspond to the speed and voltage in the network.
- Overheating of the electric motor for too long continuous operation.
Sandpaper groove
The armature shaft is fixed in the chuck of a torque mechanism (lathe, drill). Rotation starts, the abrasive is applied to the collector. Power pressure and the use of coarse sandpaper are excluded. The minimum grit value is 1000 P.
Using a multimeter, detect the presence of a breakdown in the armature winding. Set resistance test mode. Apply one probe to the lamella and the other to the contact of the corresponding winding track. The absence of an open circuit will be indicated by an audible signal. If there is no signal, this trace is broken. You will need to replace the armature or rewind its winding.
Determine if the bearings are running out. If it is found, replace the bearings and measure with a micrometer the diameter of the armature shaft edges at the points of its abutment to the assembly units.
What is it?
These components are made by mixing a carbon black substance with graphite and other binding components – hardeners. This mixture is a good conductor of electric current.
A copper wire without a winding is mounted in the "body" of each brush, to the free edge of which a plate of an individual configuration is soldered. The wire is located inside the spring, which rests with one edge against the brush, and the other against this plate. The spring has a free pressing action and the brush fits snugly against the collector as it rotates.
In other situations, sparks can be observed in the area where the brushes are located. This fact is accompanied by the characteristic sparking sound and the smell of burnt graphite. If the brushes sparkle on the angle grinder, this is a sign of a malfunction of its nodes.. In this case, you need to diagnose the device.
The reasons
There may be several reasons why angle grinder brushes spark and wear out strongly:
- Malfunction or increased wear of the brushes themselves;
- Violation of the contact density between them and the collector plates;
- Deterioration of the clamping action of the brush spring;
- Breakdown between collector lamellas;
- Axial runout of the armature due to bearing wear;
- Short circuit in the armature winding;
- Making structural damage to the mechanism during repair.
The reasons listed above are the result of improper operation of the angle grinder or poor assembly of its components.
In order to avoid the appearance of sparks in the area of the brushes, the rules for the safe use of the angle grinder should be observed.
- Do not turn on in case of high humidity, pronounced voltage drops in the network, dirt entering the brush block, contamination of the air duct grilles in the housing.
- Avoid overheating of the engine, load, slowing down the rotation of the mechanism at the time of operation.
- Do not use a low-power angle grinder for cutting "heavy" materials.
Why do the brushes of the electric motor collector spark? Causes of sparking under the collector brushes. Spark elimination methods.
The sparking of brushes is accompanied by most of the faults in DC machines. Therefore, in itself, this undoubted sign of some kind of disorder in the car says as little to an electrical engineer as a patient’s fever tells a doctor. But once we ponder this phenomenon, ask ourselves what an electric spark is, so that the answer to this question will indicate to us two kinds of malfunctions that can cause sparking.
An electric spark is the passage of an electric current through an air gap between conductors. The weaker the current and the smaller the air gap, the weaker and more imperceptible the spark. An electric machine is built so that, if it is in good condition and working correctly, no noticeable sparking occurs, because this is far from a harmless phenomenon: sparks burn the copper of the collector and gradually destroy it, and the spark brushes quickly burn out. Consequently, if sparks under the brush are still noticed, then either the air gap between the collector and the brush, or the current strength has become greater than they should be.
Malfunctions causing sparking due to loose contact.
When the brush fits so tightly to the collector that its surface at each point is in contact with some point on the collector surface, in other words, when the contact between them is uniform and perfect, then there is no air gap between them at all.
But for this it is necessary, first of all, that both surfaces have not only exactly the same curvature, but also be completely smooth. This is why each carbon brush is carefully ground to the manifold, and the manifold is ground, grinded, and polished to be as smooth as a mirror.
But this is not enough. After all, the collector rotates under the brushes all the time. It is necessary to ensure that not only with a stationary collector, but also with its rotation, the contact with the brush is not interrupted or weakened at any point. The slightest contamination, clogging of the collector is enough, the slightest tremor of the whole machine or any part of it is enough for the brush to start bouncing on the collector, and then small air gaps appear between them and sparks in these gaps.
Finally, the manifold must be perfectly round and perfectly “centered”, that is, its axis must be aligned with the axis of the machine and the brush yoke. Otherwise, the collector, when rotating, “hits”, presses against the brush with some of its plates stronger, others weaker, and then the brush again jumps and sparks.
If these are the conditions for good contact, then it is easy for us to list violations of these conditions.
1. The rubbing surface of the brushes is in an unsatisfactory condition. For example, in copper brushes it is dirty, burnt, serrated; for coal brushes – it is furrowed with grooves, where copper dust is crammed, broken off at the edges or poorly ground.
2. The rubbing surface of the collector is in an unsatisfactory condition, for example: a) rough (scratched by the edges of the brushes, burned with sparks), b) wavy (dug by grooves under the brushes), c) the edges of mica gaskets protrude above the copper plates of the collector, by which they are separated.
3. The rubbing surface of the manifold is dirty or clogged. A) It can be contaminated primarily by carbon brushes when they are too soft, because they crumble and cover the collector with sticky coal dust; b) the collector is also contaminated with excessive lubricant – the substance used for lubrication (oil, paraffin, petroleum jelly, etc.) gradually forms an insulating layer, pierced by sparks; c) with insufficient care, the collector is gradually clogged with copper, coal and other dust; d) when the room contains acid vapors or gases (for example, a gas generating power plant), then the copper plates of the collector chemically decompose and it becomes covered with a layer of oxide, even if the machine is not working.
4. The brushes are too loose on the collector, because the pressure springs are not tightened.
5. The collector trembles a) at the same time with the machine or b) because it is loose itself. The bond between its plates can gradually loosen because the clamping ring screws are loosened or because the insulating material between the plates and the manifold bushing softens. Then the insulation between the plates also appears.
6. The brushes are shaking a) with the machine or b) with some part of the brush apparatus. The entire brush yoke, one of its bolts, the brush holder on the bolt, the brush clip in the brush holder, and the brush itself in the clip can loosen.
7. The collector “hits” a) together with the armature and the shaft or b) by itself.
Along with the anchor, the collector hits when the bearing shells are triggered or when the bearing frame, located not on the common foundation plate with the machine, has settled.
Fault 7b can be caused by looseness of the collector (see 5b), uneven wear of the collector plates when they are of different hardness, and improper centering of the collector during its assembly.
Sparking due to short currents
closures.
The following malfunctions are possible, causing sparking, as a result of such a short circuit:
8. Increased machine speed.
9. Incorrect position: a) the entire brush yoke or individual brushes.
When the armature rotates in this field, the conductors of one of the circuits cut through more lines of force at each moment than the conductors of the other, so that the former have more electromotive forces than the latter. For the uniformity of the magnetic field, it is necessary that all its poles are excited equally strongly and that along the entire circumference of the armature the air gap between it and the circumference of the poles, the so-called inter-iron space, remains unchanged.
A. Sparking as a consequence of equalizing
currents with uneven magnetic field.
10. The anchor “hits” for the same reasons that are indicated for the fault 7a.
11. One or more of the magnetic coils, in whole or in part, are short-circuited. This can happen as a) due to damage to the insulation of the magnetic coils, and b) due to its moisture (accumulated in a damp room or during the transport of the machine).
12. The magnetic coils are mistakenly turned on incorrectly, so the poles are not alternating correctly. Then, of course, the magnetic field is not only weakened, but also distorted.
B. Sparking as a consequence of equalizing
currents with different resistances in
parallel chains of the armature winding.
13. One or more turns of the armature winding are short-circuited. Such a closure can occur in various ways.
14. Looseness of contact between the ends of the anchor conductors and the collector plates due to poor soldering or loosening of the cockerels (screws with which these ends are connected to the plates in some machines).
15. Breaks: a) in the connections between the ends of the armature conductors and the collector plates or b) in the anchor conductors themselves.
Sparking as a result of increased operating current.
16. The machine is overloaded a) intentionally or b) due to significant current leakage (poor insulation) in the external network or c) due to excessive friction in the machine.
17. The voltage is too low due to a weakening of the magnetic field, which can occur a) due to a decrease in the speed of the prime mover, since we are talking about a dynamo or b) because the driving current of the magnets is weakened, for example, too strong is left in its circuit by mistake the regulating resistance or some of the magnetic coils are incorrectly switched on (see fault 12).
These are the main faults with arcing. Having finished listing them, we must make a reservation. We divided them into two groups: a) weakening of the contact (between the collector and the brush) and b) increased current in the brush, and within the second group we distinguished short-circuit current, equalizing current and operating current.
But it must be borne in mind that this distinction is to a certain extent artificial, although it facilitates an overview of possible malfunctions. Sparking often occurs for more than one reason. They can act independently of each other, and they can depend on one another.
For example, weakening of the contact can occur due to several, simultaneously occurring malfunctions from among those listed under the numbers 1-7. On the other hand, the weakening of the contact is often necessary in connection with the increase in the current in the brush; for example, when the anchor strikes (see 10). Then at the same time it hits the collector (see 7a). For the first reason, an equalizing current passes through the brush, for the second, its contact with the collector weakens. Both causes sparking. Finally, an increase in the current in the brush can be caused by an increase in the operating current and the occurrence of equalizing currents. This happens, for example, if the magnetic coils are switched on incorrectly (see 12 and 17).
(6 estimates, average: 4.33 out of 5)
Why electric motor brushes sparkle
Collector electric motors differ from other types of motors by the presence of a collector-brush assembly. The unit provides electrical connection of the rotor circuit to the circuits located in the stationary part of the motor and includes a collector (a set of contacts located directly on the rotor) and brushes (sliding contacts located outside the rotor and pressed against the collector).
During the operation of the commutator motor in a power tool, sparking of the brushes can sometimes be observed. In some cases, this symptom leads to an early breakdown of the power tool, and in some. Does not bode well. One way or another, it is useful in each case to understand what is the cause of the sparking, so that, if necessary, take the right measures in a timely manner. In this article, we will look at the causes of brush sparking, as well as measures to combat the problems causing this phenomenon.
Root cause
Obviously, the intermittent mechanical contact of the brushes with the collector cannot but lead to arcing, because in fact, the rotor’s electrical circuit breaks and closes again many times a second.
The rotor contains a winding, which is a predominantly inductive load. The rupture of such a circuit is inevitably accompanied by a transient process, which is associated with the appearance of small arcs from the self-induction of the rotor winding or the rotor and stator windings. Of course, brushes wear out over time, as do the collector plates, but sometimes problems arise even before they wear out.
For the sake of fairness, we note that for the above reason, even a serviceable collector engine cannot work without sparks at all, there is always a small spark on the collector. A fully functional device normally reaches full power, develops working speed and still sparks a little. It’s another matter if the sparking is strong – this is where justified concern arises.
Sparking brushes as a sign of wear
If the brushes are already badly worn out, simply due to the age of the engine, then the engine will not be able to reach full speed and reach full power. In this case, the sparking will be very strong, and the engine will not start the first time.
How can you verify that this is the case? If the worn brushes are pressed against the manifold with a screwdriver, the contact will become tight and the engine will start. But as soon as the clamp is loosened, sparks will reappear – the distance between the plates and brushes will be filled with small arcs. The brushes are clearly worn out – they should be replaced with new ones. Sometimes replacement is only possible together. With brush holders and springs.
There may be a short circuit in the rotor winding
The armature (rotor) winding of a collector motor traditionally contains several sections. If at least one is damaged, if there is an interturn short circuit, then more current will be supplied to one section than to the others. This will lead to overheating of the winding in one place, and to uneven sparking on the collector – on some transitions on the plates, sparks will be stronger than on others. This requires rewinding an anchor or a completely new anchor.
Is the stator winding OK?
A similar malfunction is possible inside the stator, when part of the winding overheats, and strong arcing is observed near one of the brushes. Check the resistances of both halves of the stator winding, they must be the same. If one of the parts of the stator winding has a resistance that is much lower than that of the other, then rewinding or replacement of the stator is required.
A dirty collector is the reason for an unnecessary short circuit on it, as a result, extra sparks appear
The dust on the collector is formed as a result of gradual wear of the brushes – this is graphite dust. It accumulates between the plates (lamellas) of the collector, and creates "unauthorized" closures. Sparks appear due to short circuits. Simply clean the collector with sandpaper to remove any dirt between the lamellas.
Be sure to check how the brushes are located, whether one of them is displaced relative to the normal position, correct the brushes if necessary. When the brushes are positioned crookedly, graphite dust is generated in prohibitive amounts than with the correct positioning of the brushes.
Another reason for contamination is carbon deposits on the collector due to overheating. When all other causes of sparking have been eliminated, it is necessary to clean the contacts from carbon deposits in order to improve the contact of the brushes with them.
If the contact is good, the resistance does not increase beyond the rating, and unnecessary sparks do not arise. You can clean off carbon deposits like graphite dust. Sandpaper, only rotating the rotor with the collector clamped in special pads.
Why electric motor brushes sparkle
Collector electric motors differ from other types of motors by the presence of a collector-brush assembly. The unit provides electrical connection of the rotor circuit to the circuits located in the stationary part of the motor and includes a collector (a set of contacts located directly on the rotor) and brushes (sliding contacts located outside the rotor and pressed against the collector).
During the operation of the commutator motor in a power tool, sparking of the brushes can sometimes be observed. In some cases, this symptom leads to an early breakdown of the power tool, and in some. Does not bode well. One way or another, it is useful in each case to understand what is the cause of the sparking, so that, if necessary, take the right measures in a timely manner. In this article, we will look at the causes of brush sparking, as well as measures to combat the problems causing this phenomenon.
Root cause
Obviously, the intermittent mechanical contact of the brushes with the collector cannot but lead to arcing, because in fact, the rotor’s electrical circuit breaks and closes again many times a second.
The rotor contains a winding, which is a predominantly inductive load. The rupture of such a circuit is inevitably accompanied by a transient process, which is associated with the appearance of small arcs from the self-induction of the rotor winding or the rotor and stator windings. Of course, brushes wear out over time, as do the collector plates, but sometimes problems arise even before they wear out.
For the sake of fairness, we note that for the above reason, even a serviceable collector engine cannot work without sparks at all, there is always a small spark on the collector. A fully functional device normally reaches full power, develops working speed and still sparks a little. It’s another matter if the sparking is strong – this is where justified concern arises.
Sparking brushes as a sign of wear
If the brushes are already badly worn out, simply due to the age of the engine, then the engine will not be able to reach full speed and reach full power. In this case, the sparking will be very strong, and the engine will not start the first time.
How can you verify that this is the case? If the worn brushes are pressed against the manifold with a screwdriver, the contact will become tight and the engine will start. But as soon as the clamp is loosened, sparks will reappear – the distance between the plates and brushes will be filled with small arcs. The brushes are clearly worn out – they should be replaced with new ones. Sometimes replacement is only possible together. With brush holders and springs.
There may be a short circuit in the rotor winding
The armature (rotor) winding of a collector motor traditionally contains several sections. If at least one is damaged, if there is an interturn short circuit, then more current will be supplied to one section than to the others. This will lead to overheating of the winding in one place, and to uneven sparking on the collector – on some transitions on the plates, sparks will be stronger than on others. This requires rewinding an anchor or a completely new anchor.
Is the stator winding OK?
A similar malfunction is possible inside the stator, when part of the winding overheats, and strong arcing is observed near one of the brushes. Check the resistances of both halves of the stator winding, they must be the same. If one of the parts of the stator winding has a resistance that is much lower than that of the other, then rewinding or replacement of the stator is required.
A dirty collector is the reason for an unnecessary short circuit on it, as a result, extra sparks appear
The dust on the collector is formed as a result of gradual wear of the brushes – this is graphite dust. It accumulates between the plates (lamellas) of the collector, and creates "unauthorized" closures. Sparks appear due to short circuits. Simply clean the collector with sandpaper to remove any dirt between the lamellas.
Be sure to check how the brushes are located, whether one of them is displaced relative to the normal position, correct the brushes if necessary. When the brushes are positioned crookedly, graphite dust is generated in prohibitive amounts than with the correct positioning of the brushes.
Another reason for contamination is carbon deposits on the collector due to overheating. When all other causes of sparking have been eliminated, it is necessary to clean the contacts from carbon deposits in order to improve the contact of the brushes with them.
If the contact is good, the resistance does not increase beyond the rating, and unnecessary sparks do not arise. You can clean off carbon deposits like graphite dust. Sandpaper, only rotating the rotor with the collector clamped in special pads.