The History of Electric Motors

In practical terms, the year 1866 can be considered as the year of birth of the electric machine, as it was on this date that the German scientist Werner Siemens invented the first self-induced direct current generator. However, we must mention that this electric machine, which revolutionized the world in a few years, was the last stage of a process of studies, researches and inventions of many other scientists, for almost three centuries. Dobrowolsky developed, in 1891, the first series production of asynchronous motors, in the powers of 0.4 to 7.5kW.

It was the electrical engineer Dobrowolsky, of the AEG firm of Berlin, that persevering in the research of the AC motor entered, in 1889, with the patent application of a three-phase motor with cage rotor. The engine featured had a power of 80 watts, an approximate efficiency of 80% in relation to the power consumed and a great starting torque. The advantages of the squirrel cage rotor motor over the direct current were striking: it had simpler construction, quieter, less maintenance and high operating safety.


The most basic of all types of electric motors is the squirrel box induction motor which is used with three-phase power. The armature of this type of motor is in three fixed coils and is similar to the one of the synchronous motor. The rotating element focuses on a core, which includes a series of large capacity drivers placed  in a circle around the tree and parallel to it. When they do not have the core, the rotor drivers look in their shape to the cylindrical cages that were used to hunt squirrels.

 The flow of the three-phase current inside the coils of the fixed armature causes a rotational magnetic field, and this induces a current in the drivers of the cage. The magnetic reaction between the rotating field and the rotor drivers that carry the chain causes it to turn. If the rotor rotates at exactly the same speed as the magnetic field, there will be no induced currents in it, and therefore, the rotor must not rotate at a synchronous speed. In operation, the rotational speed of the rotor and that of the field differ from one another by 2 to 5%. We call that difference in speed.

Internal Engine Forces

The internal forces of the electric motor cause the rotor to rotate, which is called the Lorentz Force. If an electron passes through a magnetic field, it will suffer a force. If there is a current passing through a wire through the magnetic field, it will suffer a force proportional to the product of the current and the magnetic field.

To maintain the constant torque in the rotor two things can be done as, reverse a half cycle of the current in the whole winding and doing this the torque will always be in the same direction, will not be alternated, and also the additional windings can be placed with different angles around of the motor, causing the torque to become the sum of the torques of these windings rab vxcb . This is always greater than zero, but not constant, this variation being called the ripple of the torque.

We can calculate the direction of the force using the Right Hand Rule. The index finger of the right hand points in the direction of the current and the middle finger points in the direction of the magnetic field, the thumb will give the direction of the force. Note that the single wire will be replaced by a loop. The forces on this wire will cause a rotation in the loop and between the magnetic poles, this loop will behave like two wires with currents flowing in opposite directions.

Magnetic Fields with Heavy Load

The curve assigned to the electric torque against slip can be divided into approximately three regions: The first is the region of small slip of the curve, in which it develops with increasing load and the mechanical speed of the rotor decreases with the load. The power factor of the rotor will be almost unitary, even if the rotor current rises with slipping. The normal operating range of the induction motor is within this linear region of low slip. The second region of the induction motor curve may be called the moderate slip region in which the rotor frequency is higher than before and the rotor reactance is of the same order as the rotor resistance. The maximum torque of the motor lies at the point where the increase in the rotor current is balanced exactly with the reduction of the rotor power factor.


The third region of the induction motor curve is of great slip, in which the induced torque actually softens with the increase of the load, because the increase in the rotor current is not remarkable due to the decrease in the power factor of the rotor.

Starting Capacitor Motor

The electric motor with capacitor of starting is a motor similar to the one of split phase, having as difference the inclusion of a capacitor electrolytic in series with the auxiliary winding of start. The capacitor admits a larger angle of lag between the main and auxiliary winding currents, thus providing high starting torques. As in the split-phase motor, the auxiliary circuit will be switched off when the motor reaches 75% to 80% of the synchronous speed. In this range of speeds, the winding alone develops almost the same torque as the combined windings.

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For higher velocities between 80% and 90% of the synchronous speed, the torque curve with the combined windings crosses the torque curve of the main winding so that at speeds above this point the motor will develop less torque and for any slip, with the auxiliary circuit connected than without it. Because the curves do not always intersect at the same point, and the centrifugal breaker does not always open at exactly the same speed, it is a common technique to make the aperture occur, on average, just before the curves intersect.

The Hall Effect

Commercially we can find Hall Effect sensors both in their simple form and in bridge configuration. One of the advantages of using the bridged configuration is that it supports detecting field variations in both directions, simplifying the design of detector circuits. Hall effect sensors can be defined as being transducers that vary their output voltage in response to a magnetic field.

The operation of these sensors is based on the Hall effect. The effect of Hall determines that in a magnetic area traveled by a current which we will measure the voltage drop, we find that it will be zero volts. But when applying a magnetic field to this same area, a small voltage best prices for SKF-Bearing will appear between the two ends. The difference of these two tensions is due to the existence of a force to move the electrons along the magnetic area (Force of Lorenz). It is with the information of this potential difference that the Hall effect sensor acts. These sensors are generally best used for measuring rotor speed in electric motors and not in position.

DC Motors

DC electric motors offer the peculiarity of being the first motors to be manufactured, which is easily explained, since the distribution of energy was made in direct current (DC). Currently the main types of direct current motors are Conventional DC Motors (with brushes) and Brushless DC Motors (brushless). The operating principle of a DC machine is based on the creation of an inductor field. This field is established by the current flow in the stator coils, and they are enclosed in the stator grooves.

In the case of motors with permanent magnets, these coils are replaced by magnets, which are responsible for the creation of the inductor field. The rotor is of the wound type, whose current through its windings creates a magnetic field, the intensity of which depends spontaneously on the value of the current that runs through the windings. The interaction between the stator magnetic field and the rotating magnetic field will create the rotational motion of the motor. The control of speed of this type of motor is done through the voltage of the same, since this one is directly related to the speed. best options for baldor motors

Asynchronous motors

Asynchronous electric motors are when compared to all rotating electric motors in manufacturing, which is used more in the industrial sector. Both stator and rotor conduct alternating current. The current acting on the rotor is an induced current, this is because of a variable magnetic field in conjunction with the rotor winding. This variable magnetic field in relation to the rotor winding is caused by the difference in rotational speed of the rotor and the rotating magnetic field. That is why the electric motor induction terminology.

The induction motor can operate both as a motor and as a generator baldor ac motors, but the characteristics of the motor operating as generators are not appropriate and therefore is normally used as a motor. Unlike the DC motor, the induction motor has a uniform air gap. The rotor may have a squirrel cage or winding type fabrication. The stator coils are installed along the air gap so as to better benefit from the ferromagnetic material and thereby optimize the driving magneto force distribution, attenuating the torque created by the motor.

Agências duplas, como afirmado acima, representam o comprador e o vendedor.

Um histórico ruim significa que ou o corretor não vendeu muitas casas ou as
casas foram vendidas por muito menos do que o preço inicial pedido. Fora das
condições econômicas que podem influenciar isso, esses fatores são sinais de
alerta de que este corretor pode não estar equipado para vender sua
casa. Também é aconselhável perguntar há quanto tempo as casas ficaram no
mercado. Se o agente do seu vendedor for leal a você e ao comprador, pode
surgir um conflito de interesses. Nenhuma experiência em vender casas como
a sua também pode ser um sinal de alerta. Uma maneira fácil de contornar isso
é perguntar sobre as qualidades das casas que eles venderam no passado e
por quanto, determinar a venda de sua casa.
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Os corretores de imóveis e vendedores são comumente confundidos com o mesmo, e embora suas
funções muitas vezes se sobreponham, é importante saber a diferença quando
se trata do processo de compra ou venda de sua casa. Um agente de listagem
para um vendedor normalmente representa o vendedor atraindo compradores
por meio de marketing, abrindo casas ou exibições e até mesmo examinando
os compradores quanto à capacidade de crédito durante as negociações.

imobiliaria conhecendo a profissão de corretor de imóveis

Uma das maneiras de começar a lucrar com o mercado imobiliário é por meio da profissão de corretor de imóveis. O corretor é o responsável por intermediar compras (e respectivamente vendas) e aluguéis de imóveis, recebendo em troca uma porcentagem da operação.

As formas de se trabalhar como corretor de imóveis

A primeira delas, é sendo um autônomo ou tendo uma empresa no ramo imobiliário. A segunda, é trabalhando para uma corretora de imóveis. Nesse último caso, normalmente há uma remuneração fixa com uma porcentagem sobre as vendas.

A comissão do corretor de imóveis pode variar de 6 a 10% e pode ser consultada através da tabela do CRECI do seu estado.

Para ser corretor é preciso estudar e se tornar um bom vendedor

Lucrar com o mercado imobiliário  imobiliaria em bauru sendo um corretor de imóveis não é uma tarefa fácil. Para tal, é preciso se tornar o famoso “bom de lábia”, acumular muitos contatos e ter uma extrema facilidade em construir e manter relacionamentos.

Para seguir na profissão e lucrar com o mercado imobiliário, é preciso fazer um curso técnico em transações imobiliárias e se registrar junto ao CRECI.