Frequency inverters

Due to the increase in demand for AC motors, there is also a growing need for equipment to control this type of motor. The application of frequency inverters is in the machinery and process industry in general and have the ability to change the speed or torque control of three-phase alternating current electric motors.

As we already know AC motors have a low acquisition and maintenance cost when compared to DC motors, which use high wear and high maintenance brushes.

Frequency inverters are electronic devices that convert AC voltage to DC voltage at constant amplitude and frequency.

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The inverters control the motor speed from zero to the maximum rated frequency. In the market there are inverters that can generate an alternating voltage (AC) of up to 7200Hz, that can feed special motors. They are able to act as protective devices for the most diverse electrical network problems that can happen.

These devices are used in electric induction motors, as they replace the rudimentary speed variation systems, as with pulleys, electromagnetic drives and hydraulic variators.

Esta entrada foi publicada em julho 28, 2017, em Uncategorized.

Three Phase System

In electric motors the three-phase circuit is composed of three alternating voltages, in which the electric energy is transmitted by means of the composition of the three voltage signals lagged 120º of a cycle with each other.

 

In the early days of the implementation of the long-distance power transmission system, thanks to the technological advancement mainly due to the work of Nikola Tesla, the alternating system for voltages and currents was used in order to allow the transport of energy over long distances without losses To the point of making the process unfeasible.

For the generation of alternating voltages and currents, synchronous generators or MIT motors are used, which in theory could provide any number of alternating voltage and current signals, equally lagged depending on the generator construction.

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For reasons of practicality, economics (material economy) and techniques (quality of energy supplied), it was decided to use the three-phase system.

The advantages of the three-phase system over the single phase are:

– For the same size, three-phase generators and motors are more powerful than single-phase motors;

– Three-phase transmission lines require less copper than single-phase transmission lines to carry the same power.

Esta entrada foi publicada em julho 18, 2017, em Uncategorized.

Motors – Mechanical Protection

Electric motors must be preserved, taking into account the protection of the persons performing the service, as well as external influences that may be harmful, and it is extremely important to consider all safety and accident and fire prevention requirements.

The motor housing has the purpose of securing it in the workplace, ensuring the protection of the same, according to the local environment where it will be installed. The casing must be designed in such a way as to encompass the different types of mechanical protection, in order to promote compliance with the requirements of the plant and machinery standards for which the engines will be designed.

In this way, the mechanical protections can be classified into three categories, they are resistant to drips and splashes, completely closed and explosion proof.

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Engines resistant to dripping with all rotating parts, or under tension, are protected against water. In fully enclosed motors there is no exchange of the cooling medium between the exterior and the interior of the enclosure. And the explosion proof are built for service in environments saturated with gases and dust. Its enclosure is resistant to explosions of gases or explosive mixtures specified inside, preventing a surrounding flammable atmosphere from being ignited.

Esta entrada foi publicada em julho 10, 2017, em Uncategorized.