Universal brushed motor: characteristics, AC motor design, repair

Almost all types of electrical equipment are equipped with powerful elements with mechanical switching. Their well-coordinated work depends on a universal brushed motor, which copes perfectly with various loads. But in order for such a unit to function properly, it is necessary to carefully study not only its design features, but also the principle of operation.

Brief description of the device

Experts are used to calling those electrical machines a collector motor where the current switch and the rotor sensor are one and the same element. It is he who provides a reliable connection of various chains in the fixed compartment of the unit with the rotor.

Its design consists of powerful brushes (these are specific sliding-type contacts, which are located near the rotating part of the motor) and the collector (this part is installed by the manufacturer on the movable unit of the mechanism).

The main advantages of such an element can be safely attributed to the fact that a high-quality engine is easy to maintain and operate, can be repaired and has a long working life. Among the shortcomings, the manufacturers themselves highlight the fact that the unit has a low weight and a large percentage of efficiency. Of course, most often these two indicators are positive, but not in this situation.

The combination of high speed (can reach several thousand revolutions per minute) and low weight is fraught with the fact that for normal operation the consumer you need to additionally purchase a good gearbox. If the car is rebuilt at a lower speed, then the level of efficiency can seriously drop, which causes problems with quality cooling.

Varieties of the lineup

The commutator motor is an AC rotating electrical machine that easily converts DC current into mechanical energy. At least one winding that participates in this process is connected to the main collector.

Almost every model consists of such elements:

1. High quality bipolar permanent magnet stator.
2. Professional three-pole rotor on specific bearings with sliding effect.
3. Copper plates used as brushes for the brushed motor.

It should be noted that this set is minimal, which is why it is often found in budget models. This also applies to children's toys, where a large working power is not needed.

In a complete set of higher quality products, usually add a few more elements:

• Multi-pole rotor with special rolling bearings.
• Four brushes made of graphite, which are presented in the form of a collector unit.
• A four-pole stator that consists of permanent magnets.

Such units used in modern cars for the arrangement of a high-quality drive for the fan of the cooling and ventilation system, wipers and windshield washer pumps. Of course, on sale you can also find more complex units that differ not only in performance and scope, but also in price.

If the power of the electric motor is within a few hundred watts, then its complete set necessarily includes a four-pole stator, which is made of special magnets. And here is a high-quality winding connection can be done in one of the following ways:

• Parallel. In conditions of fluctuating load, all revolutions remain stable, but the maximum torque is slightly reduced.
• In series with the rotor. This option differs in that the maximum moment acquires quite impressive indicators, but there is a high risk of damage to the motor, since the unit is operated by the user on large revolutions.
• Independent excitation from a separate power source. For this situation, the same characteristics are used as in the parallel connection type. It should be noted that this option is rarely used by specialists.
• Mixed type of excitation, when a certain part of the existing winding is connected in series, and the second part is connected in parallel. This configuration successfully combines all the advantages of the previous options. This type of connection is ideal for car starters.

But well-known manufacturers have provided for the presence of universal collector motors. Their key feature is that they work perfectly on both direct and alternating current. They are actively used in household appliances, power tools, as well as in railway vehicles.

Such popularity is due to the fact that they are quite light in weight and size. In addition, their price is more than affordable and each user can independently set the number of revolutions required for work. Due to this, the electric motor collector belongs to the category of alternating current devices, it shows excellent results with unstable energy sources.

Component elements of the structure

In order to properly understand the features of the collector motor device, you need to study all the component parts of this unit. After all, the device itself is presented in the form of a direct current device, where field windings are connected in series. They are designed to operate on AC household power.

Regardless of the polarity, the motor always rotates in one direction only. This feature is due to the fact that the series connection of the rotor and stator windings leads to a simultaneous change of the magnetic poles. As a result, the resulting torque is directed exclusively in the same direction.

The high efficiency of using the collector motor is due to the presence of the following elements:

• The stator is the stationary part of the installation.
• The armature is an integral part of the collector unit, in which the electromotive force is induced and the load current flows. It should be noted that both the stator and the rotor can act as an anchor.
• An inductor is a specialized excitation system. This part creates a magnetic flux for the timely generation of a torque. The inductor must be equipped with an excitation winding or permanent magnets. The part itself can act as an integral part of the stator or rotor.
• The rotor is the rotating element of the machine.
• The collector is the base part of the motor, which is in contact with the brushes (these two parts distribute the electric current over the armature winding coils).
• Brushes are part of the circuit that carries electricity from the power source to the armature. These elements are manufactured from durable graphite. A DC motor can contain from one pair of brushes or more.

Functionality of the motor

The schematic diagram of the collector motor device perfectly demonstrates how this unit converts electricity into mechanical energy and in reverse order. This suggests that such a device can even be used as a generator. When current passes through a conductor that is located in a magnetic field, certain forces are applied to it. In this case, the rule of the right hand is actively working, which has a direct impact on the final engine power. The collector unit functions according to this principle.

In the standard circuit, it is clearly shown that one pair of conductors is placed in a magnetic field, the current of which is directed in different directions in the same way as the forces. The amount formed by them gives the torque required for the equipment. In the collector motor, manufacturers have also added a whole complex of additional units that guarantee the identical direction of the current over the poles.

Due to the fact that several more coils are located on the anchor, the unevenness of the stroke has been completely eliminated. In addition, the craftsmen no longer need to use direct current, as conventional magnets have been replaced with more powerful coils. At the final stage of production, the torque took a single direction.

Pros and cons of operation

For comparison, qualified specialists used the following parameters: both units were connected to a home electrical network with a frequency of 50 Hz and a voltage of 220 V. The motor power of the devices is completely identical. The final difference in mechanical parameters can act as a huge plus or as a minus (it all depends on what requirements the user imposes on the drive).

Collector motor has the following advantages over a DC unit:

1. A lower starting current, which is especially important for the equipment used by consumers in everyday life.
2. The unit can be connected directly to the network, there is absolutely no need to install accessories. But the unit with direct current needs continuous rectification.
3. Fast speed and complete absence of dependence on the mains frequency.
4. If there is a control circuit, then the collector device turns out to be simpler - a thyristor and a rheostat. When an electronic part fails, the unit itself remains operational (but will operate at full capacity).

Do not forget about the shortcomings that must be carefully studied by each consumer even before purchasing the unit. Only in this case can you be sure that the device meets all the requirements.

Collector motor has the following disadvantages:

1. The overall percentage of efficiency is significantly reduced, since there is inductance and losses due to stator magnetization reversal.
2. Maximum torque has been significantly reduced.
3. Relatively low reliability and short service life.

Any changes in the settings are possible only if the unit is equipped with a speed controller. Different amounts of supplied electricity can change this indicator by only 10%. While a high-quality speed controller allows you to reduce their number by several times. You can make such a device yourself or buy it in a specialized store. But you need to check if it can work in the collector with a certain power and number of revolutions. If the regulator is weak, then it will simply break.

Home engine repair

Like any other device, the collector can fail at the most inopportune moment. If the electric motor does not pick up the specified number of revolutions or the shaft does not start spinning after the start, then you need to check the performance of the fuses. The problem can also be caused by an open circuit in the armature and overloading the device. Quite often, the irrational use of the unit leads to an increased current consumption. This malfunction can be eliminated only after inspecting the brake and the mechanical part.

If during operation the unit does not produce the rated number of revolutions, then this may be caused by insufficient mains voltage, overload, as well as high excitation current. If the user noticed an inoperability of the opposite type, then it is necessary to check the electrical circuit, and also to eliminate all formed defects. In some cases, the unit starts to function only after rewinding the motor.

When the device does not work due to incorrect pairing of parallels and series field winding, then the user needs to restore the correct order of connections.

Do not forget about regularly checking the voltage in the mains, as the engine speed can increase significantly.