Expression of Current Transformer Errors

To evaluate a more complex construction sometimes it is necessary to take into account the physical construction. In the first place, a general equation of errors is developed, taking into account physical relations.

In order to maintain current I2 in the secondary circuit, we need an E (induced voltage) emf in the secondary winding, which is balancing the voltage drops: E = I2 (Z2 + Zc) (21) where Z2 is the internal impedance and Zc is the external impedance.

To maintain the flow, we need an excitation, which will be the difference of the primary excitation, θ1, and secondary, θ2. In some situations, it is more practical to do the calculations by the CT equivalent circuit.

Because of the shape of the power supply the impedance of the primary winding is not influencing the distribution of the currents, and therefore is not represented. Z2 is the internal impedance, defined by the secondary winding.     boston

The next step proves that with these expressions based on the equivalent circuit, one can arrive at the same results based on the physical construction. The vacuum current I0 is expressed by the CT construction parameters. To maintain the flow, the vacuum current is needed, I0.



Direct Drive Motor

A direct drive electric motor is a direct drive motor, ie it does not require fastening elements, energy transformers such as pulleys, pulleys, racks and screws. This feature ensures that the engine gets smaller, thus taking less space.

Alternate correne motors of permanent magnets – Direct Drive have 80% efficiency, excellent controllability, are synchronous, do not need reducing gears, and are quiet. For example: an electronic washer with Direct Drive motor has a noise ratio of 53 dB and in the centrifugal function the noise level does not change, meaning the noise is almost zero.

The Direct Drive motor has a unique feature that is the durability of the components, because it does not need pulleys and chains, components that are consumed more frequently, so the engine lasts longer, without maintenance.

Direct Drive engines have high initial costs, which can be 30 to 400% higher than the cost of conventional systems, but after 5 years of life, conventional systems can cost more, being 3 to 10 times higher than Direct Drives cause of maintenance and service life.


Boot Types

When the electric motor operates directly connected to the mains, that is, with a regular three-phase power supply, the sum of all the vectors corresponding to the phases is zero, the neutral being stationary and is usually maintained in the ground. For a given voltage, the characteristic curve of the motor will be fixed, independent of the load. Being connected directly to the electrical network will present a certain starting current peak, which normally presents its maximum value and that will cause a voltage drop in the network, interfering with the devices where they are connected. If so. Then the direct start must be replaced by another possible connection in order to reduce the starting current.

The connection types commonly used are serial-parallel connection, star-delta connection, static-start connection or electronic starter connection using a frequency inverter or variable speed drive CA32112 M. Frequency inverters have been increasingly used to control squirrel cage three-phase induction electric motors because of their efficiency and competence to regulate working speed as well as other parameters.

The Motors in Appliances

The basis of the operation of many appliances we use is the rotation that comes from the electric motors and sometimes this rotating movement is obvious, as in the cake mixers or fans, but usually remains well disguised, as in the washing machine agitators or in the movements of the electric windows of automobiles windows. Widely used in our daily lives, the motors range from small appliances such as blenders and shavers to large industrial engines capable of handling tons.

With the advance of the knowledge about the magnetic field induced by the electric current, an idea appeared that would end up revolutionizing the forms of generation of work and force. The use of some natural factors and others invented and improved by great scholars of our history arise what we call electric motor, the machine destined to transform electrical energy into mechanical energy. When we connect a motor to the power grid, it absorbs the amount of electrical energy needed to move and charge a load. The large variations reach the most diverse technical specifications, some of them being of high precision, controlled electronically by drives and inverters, used in robots and automation machines.

Auxiliary Contacts

The auxiliary contacts of a contactor must strictly follow a specific category of numbering, taking into account that the number is properly formed by two digits, the first digit indicates the contact number and the second digit indicates if the contact is from normally closed type, one and two, or normally open, three and four. If the auxiliary contacts are numbered, they must follow a standard, and one and two are normally closed contacts, NF, with 1 being the input and 2 being baldor M1025T the output. And three and four are the normally open contacts, NA, with 3 being the input and 4 being the output.

In this way, in the relays and contactors have A1 and A2 for the coil terminals. The numbering of the contacts representing the force terminals is shown as follows, one, three and five are of the input circuit, line. The two, four and six are from the output circuit in the terminal. In the same way that each element present in an electric control circuit has its specific graphic symbol, the numbering of the contacts and the literal representation of them also has a standard that must be respected and followed.

Temperature Limits

A possible sudden drop in voltage can limit the flow of the magnetic circuit, which can result in a significant reduction of losses in the iron as well as the current in a vacuum. However, the motor torque must exceed the strength torque, so that it is capable of impeding the slip lift. As the motor torque results from the process between the flow and the intensity of the absorbed current, if the flux decreases, the current intensity automatically increases. With the load current raised by the voltage drop, the motor will heat up, thereby increasing the losses.

In this way, the maximum temperature limitation that can be supported by the insulation components of the motor must be calculated for its effective operation in a location which contains an average temperature of approximately 40 ° C. Therefore, it is extremely important that the operator responsible for the maintenance, performs the proper control of the ambient temperature, in order to ensure that it does not exceed the determined values ​​for which the engine was manufactured. Some measures should be taken regarding voltage variations. In this way, the thermal equilibrium of a motor is consequently modified according to the variation of the supply voltage.

Different categories of Motors

It is noteworthy that most AC motors count on average with two elements considered as main and essential, consisting basically of a stator and a rotor. The stator refers to a slotted metal ring that holds the coils of insulated wire in a steel core. The alternating current passes through the entire length of these wires in order to produce a rotating magnetic field.

It can be stated that one of the main differences between the electric motor of alternating current and the electric motor of direct current, besides the power supply, consists of the form of control of the speed, that varies according to the tension applied and this relation can be linear, making speed control and calculations more simplified.

In this way, electric motors of alternating current are devices that have their power in alternating current. Electric motors are used in the conversion of electrical energy into mechanical energy, with the main mission of producing work in a system. The AC motor is used in the production of power for a wide variety of systems, ranging from small servomechanisms to large industrial machines.

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As soon as the electric motor is driven into the network, the coil is properly fed and the armature is drawn against the electromagnet shell, thus gaining the spring resistance. These tablets, when free, move axially in their housings, thus moving away from the friction surfaces. This ends the braking action, allowing the engine to start freely. When the motor is disconnected from the mains, the control instantly interrupts the coil current and the electromagnet stops acting. Thus, the pressure springs push the armature toward the rear cover of the engine.

The pads, installed on the brake disc, are compacted between two friction surfaces, the armature and the cap, and brake the engine until it stops completely.

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The braking system allows three connection systems, allowing slow, medium and fast braking. In slow braking, the brake coil rectifier bridge power is supplied directly from the motor terminals without any pause. In medium braking, a contact is interleaved to pause the power supply current of the rectifier bridge in the circuit. In rapid braking, the interrupt contact is inserted directly into one of the coil feed wires.

Thermal Principles of Thermorresistors

Thermoresistors consist of temperature sensors with operating principle based on a property that some components that can vary the electrical resistance with change of temperature. These sensors have a calibrated resistance that can vary linearly according to their temperature, allowing continuous monitoring of the motor heating process by a controller display, with a high degree of sensitivity and return accuracy. The two-wire configuration is often satisfactory in environments where the length of the sensor cable to the instrument does not exceed 3m for 20 AWG gauge.

In the configuration of three wires, the most used by industries, there is a compensation of the electrical resistance by the third wire. In the four-wire configuration, which requires a more precise assembly, there are two connections for each terminal of the bulb, two wires for voltage and two for current, thus obtaining a total balance of resistances, usually used in cases where High precision is required. This same sensor can also operate as an alarm for operations that occur above the common working temperature.

Transformers and Their Use

Transformers have an important role, but they have a high cost. In general, they are the most expensive equipment of a project, as well as their peculiarities of transportation, assembly, energization, operation and protection stages, so it is of the utmost importance that professionals Involved in any of these steps are properly trained.

Transformers are equipment used to transfer energy from one side of the circuit to the other through a magnetic flux common to both sides. With the exception of the autotransformer, where there is no electrical connection between the parts of the interconnected circuits through this equipment.

The transformer acme transformer 2017 is defined as a static equipment with two or more windings which, by electromagnetic induction converts an alternating voltage and current system into another system, generally being a different voltage and current system from the original system, maintaining the frequency.

The standard specifies that such conversion is intended for the transmission of electrical power and when operating as control equipment, its purpose is not to transform large amounts of energy, but to produce small variations of phase voltage or both.

The transformers are constructed in such a way that their conversion ratio can be induced under vacuum or even under load with the aid of motors.


Electromechanics consists basically in the field of science and technology, where the analysis, design, development, production and maintenance of devices that integrate electrical and mechanical components in its mechanism are carried out.

Examples of electromechanical devices include electric motors for appliances such as fans, refrigerators, washing machines and hair dryers, for example. All of these electrical devices have as main function to convert electrical energy into mechanical energy.

Considering the fact that all electromechanical elements integrate with components known as electrical and components known as mechanics, it does not mean that electrical and mechanical devices can keep physically separate and act independently of others.

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In this way, the energy is received or generated by the components, changing according to their nature and application of a specific equipment. The electromechanical energy conversion factor can also provide storage, as well as the transfer of electric energy.

The main mission of electromechanical engineering is the analysis of the principles of electromechanical energy conversion and the development of models for the components of electromechanical systems.

Electric Motors in Aggressive Environments

Environments considered aggressive, such as port facilities, fish industry and multiple marine applications, shipyards, chemical and petrochemical industries, among others, require that the equipment used in these places be rigidly adequate to bear such circumstances with reliability, without presenting problems of any kind.

For application of electric motors in these hostile locations, specific types of motors are required, manufactured to meet special requirements to deal with harsh and adverse conditions that may be encountered. These motors may have specific features such as double-impregnated winding, alkyd anti-corrosion paint, zinc-plated mounting elements, seal for shaft-to-cap application and additional protection between through joints.

For environments with low or very high temperatures it is recommended to use an anticorrosive paint. In the case of marine engines, the specific operating characteristics depend on the type of load and on-board weight.

In order to verify that the motors may or may not work in these aggressive locations, the approximate size and quantity of the fibers contained in this environment must be reported. If a large amount of dust gets on important parts of the motor, it can act as a thermal insulation, and larger fibers can also cause obstruction of the ventilation, damaging the cooling system.

Principle of Operation of Asynchronous Motors

In this type of electric motor, the permanent magnet is installed on a metal disk, affixed by a pin in an iron bearing. The magnetic flux formed by the permanent magnet passes through the series magnetic circuit generated by the permanent magnet, the air gaps and the iron plate.

When rotating the permanent magnet, the disc that is under the magnet also rotates. The disk follows the rotational movement of the permanent magnet, this occurs due to the circulation of induced currents. These currents are induced due to relative movement between the disc and the permanent magnet.

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Induced currents tend to form, in accordance with Lenz’s law, a south magnetic pole on the disk under the rotating magnetic north pole of the permanent magnet, as well as a magnetic north pole on the disk under the rotating magnetic south pole of the permanent magnet.

While the magnet remains its movement relative to the disk, the induction of parasitic currents and magnetic poles with opposite polarities will continue. The disk thus rotates in the same direction as the permanent magnet, but must rotate at a slower speed to have a related speed between the metal disk and the permanent magnet.

Electric Motor Fuses

In electric motors and other equipment, fuses are used with the purpose of limiting the current of a circuit, providing the interruption when we have a short circuit or overload. Short circuit is an intentional or accidental connection between two points of a system, electrical equipment or a component. Under these conditions the current assumes a value many times higher than the operating current, thus causing the equipment and part of the plant to undergo excessive thermal or electrodynamic stress.

Its performance is due to the casting of an element by the Joule effect, caused by the elevation of current in a given circuit. The fuse has properties where its melting point is less than the melting point of copper, which is the material most commonly used in general purpose conductors.

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They are composed of a conductor of reduced section, mounted on a base of insulating material and when overload occurs the fusible link fuses, ceasing the passage of electric current, avoiding damages to the installation and equipment.

In motor fuses, the rated current is the current value that the fuse must withstand and the breaking current is the maximum value it will break.

Foundation for Motor Installation

For the installation of electric motors, the foundation design should ensure that we have safe operating conditions with maximum accessibility.

It is very important to leave free space around the machine to ensure free access for maintenance and monitoring.

The cooling air must enter and exit the machine without problems and we must take care to ensure that other equipment that is nearby does not heat the cooling air of the machine or its parts.

The foundation must be solid, rigid, flat and free of external vibrations and all vibration and resonance of the machine in relation to the foundation must be checked, thus avoiding excessive vibrations.

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For the installation of the machines, a concrete foundation is preferable, but a correctly designed steel construction is also accepted. The fixing of the electric motor, the supply of air, water, oil and cable channels, as well as the foundation holes must be observed prior to construction.

The foundation should be designed so that 2 mm shims are placed under the machine feet to ensure fit and facilitate a possible replacement machine installation.

Electric Motors – Definitions

The electric motor is a machine designed to transform electrical energy into mechanical energy. It has evolved over time to suit different applications.

In 1885, Galileo Ferraris, an Italian physicist, based on the studies of Michael Faraday’s electromagnetic induction law shown in 1831, developed the asynchronous electric motor of alternating current which can also be synchronous or asynchronous, single-phase or three-phase.

With regard to the power supply of electric motors we have two items, namely: the dimensioning of the power cables and the characteristics of the service network.

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NBR is the acronym for: Brazilian Rules of Regulation. The standards of NBR 17094 indicated for voltages and frequencies must be obeyed in relation to the characterization of the electrical network. Already for the dimensioning of power cables of the electric motors determined by its nominal current, it must obey the indications of the NBR 5410.

Over time, various types and models of electric motors have been developed, and these have been improved according to the needs that have arisen. Today, electric motors are found in various shapes and sizes, each suited to their task, no matter how much torque or power an engine needs to develop.

Universal motor and its operation

A true direct current (DC) electric motor does not accept AC power, because this power inverts the current sense every half cycle, and that would only cause the shaking. Likewise, a true AC motor does not accept DC power, as this supply will not offer the appropriate changes in the current direction for the correct operation of the motor.

However, if we replace the permanent magnets of the stators of the DC motors with electromagnets and connect (in series) these electromagnets in the same circuit of the rotor and commutator, we will have a universal motor. If the DC motor is supplied with DC power, it will not reverse its direction of rotation. If you reverse the polarity of the source it will continue to rotate always in the same direction, working properly.

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A more powerful universal electric motor can be obtained if modifications are made to your design.

Universal motors are widely used in electric mixers, vacuum cleaners and various other appliances. In these devices, the wear time causes wear on the carbon brushes and will need to be replaced. It’s very simple. Just buy a pair of brushes for new ones, and you put it back in the engine yourself.

The Efficiency of Brushless Motors

In terms of efficiency Brushless motors always work in optimized performance conditions and because they do not have to generate the magnetic field of the rotor, they have a higher efficiency. In this type of permanent magnet motors that are positioned in the rotor, and are made with special materials, they allow to have an extremely precise control of the speed and the acceleration.

With lower costs of electronic control systems, produced by economies of scale, it became prominent of greater convenience and consequent extension of the use of motors, even without brushes for the operation of two-wheeled vehicles, motorcycles and power-driven vehicles Power.

The main disadvantage of this type of electric motor is the high cost. Unlike brushed motors, verification is performed electronically by a controller, an electronic device provided by the motor manufacturer or by a third party, so the cost of the motor must be added to the cost of the control system. For motors with brushes the “control” is performed by a rheostat, not very efficient but extremely cheap system. rab landscape fixtures

Single Electric Motor

Many people need to use a simple electric motor for applications that are basic, today the market has at their disposal or single-phase model in three-phase. When we are talking about a simple procedure the most indicated is the use of the single phase model, it is perfect for these occasions.

When it comes to a more complex application, the indicated one is to use the three-phase electric motor. The customer has to know about which of the models will meet their needs so that he can make the correct purchase of the product. The store itself can provide more information about the ideal product for what you need. radial ball bearings

One of the advantages is that the single phase model has a much more affordable value than the three phase model. Both serve the same purpose, the function of these machines is to make the transformation from electrical energy to mechanical energy in a much more economical and efficient way.

Indirect starting system of electric motor

Using the indirect starting system is the most viable solution for the electric motor

The great problem of applying direct startup to the three-phase electric motor and its high current value, since it can appear at the time of departure due to the need to overcome the inertia that exists so that it leaves the rest and therefore, the use Of the indirect starting system is the most viable solution for the electric motor.

The indirect starting of the three-phase electric motor is classified as basic, since the method used to carry out the reduction of this starting current and which interferes directly in the dimensioning of the electric devices and also of the responsible conductors that cause the motor to start Three-phase electric. hydraulics and pneumatics hose reels

One of the great problems of direct starting in the electric motor is its high electric current value at the start of the electric motor, since it needs among other things to have robust components and cables in the installation and this generates a high cost in energy consumption Power.

Learn more about some types of electromotive motor

There are several models of electric motors, but the most common are: electric motor of direct current and electric motor of alternating current.

The DC electric motor needs a direct current to make use of its rectifier circuit and thus make the alternating current to be transformed into direct current that is the same as provided by the utility grid.

The Weg high efficiency electric motor has the most sophisticated technologies in its design, which ensures that they are compact machines with excellent dynamic properties, in order to meet the most varied applications in the areas of automation and control of procedures.

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The alternating current is the most used in the electric motor, because it is this modality that the dealerships make available. This electric motor is rotary is powered by electric power mo. Unlike other electric motors, this electric motor has no need of any warehouse to its power and its essential objective is to rotate a second coupled or moved.

Electric motor can run on an automotive battery

A very common doubt for those who have electric motor is whether the automotive battery can be used to power the electric motor and the answer to that doubt is: yes, the automotive battery can power the electric motor.

However, because the battery is not suitable for this purpose, its useful life will suffer a considerable reduction and, still, it will be necessary to take another battery so that the lack of energy does not disturb the day of fishing.

For the electric motor it is possible to use two batteries that have the same amperage, however they have different applications that are: automotive and deep cycle and the second is that will allow the electric motor to run longer.

Twenty years ago, there was only an electric motor for fresh water, but already in the 90’s, the marinized models began to emerge and they started to be used in salt water, because it has special paint, its wiring is made with copper, the connections Are protected from possible infiltrations, the plates are sealed and other features that ensure a long life to the marinized electric motor.