Frequency converter: a key device for regulating the speed of an electric motor
Frequency converter – a key device affecting the operation of the electric motor. Its task is to regulate the speed of the electric motor…
The frequency converter is one of the important components affecting the operation of the electric motor. Its task is to regulate the speed of the electric motor . As the name suggests, this is achieved by changing the frequency and at the same time changing the voltage, and if the voltage is within the required values, then only by changing the frequency.
Frequency converters are used in three-phase electric motors and are necessary when it is necessary to achieve different permanent speeds. This means that the frequency converter can change the speed of rotation continuously, but also in steps, or participate directly in the control of the output torque.
Frequency converters can also be used for smooth start-up and run-down of the electric motor , without having to face current or mechanical shocks. At the same time, the frequency converter performs best when the drive is starting up. And as you probably already guessed, its use is also a way to significantly save on the energy needed to run the engine . In other cases, it is necessary to install a throttle valve and similar solutions that lead to energy loss. In applications, speed regulation also leads to optimization of productivity or an increase in its quality. The costs associated with the purchase of the inverter are thus returned in a short time interval.
Operation of the frequency converter
The inverter is supplied with alternating voltage at the input , either single-phase or three-phase. The voltage is rectified in the internal circuits, and at the output the converter offers a three-phase alternating voltage with the desired frequency. The inverter can be used for two types of loads. The first is constant load , which is most often encountered in various conveyors, machine tools, crushers, mills, etc.
The second load is the so-called quadratic load , i.e. an application during which there is a quadratic growth of the load. We can meet this type of load with various centrifugal pumps or fans. While a constant load is denoted by the letters HO , i.e. the English abbreviation for High Overload, a quadratic load bears the letters LO , i.e. Low Overload.
Converters are mostly capable of changing frequencies from 0 to 650 Hz . Thanks to this, it is possible to regulate the revolutions continuously in both directions and in the full range of permitted revolutions, because this range exceeds the permitted range of asynchronous motors.
Control and protection
Control of the frequency converter usually takes place through the control panel , which requires manual interventions in the operation of the converter. However, such converters can also be found that are able to operate automatically thanks to external control elements. And the third variant is the remote control of the converter through one of the control systems.
If you choose a frequency converter, always pay attention to a sufficient number of protective functions. Modern converters should offer a whole range of them and they should serve not only to protect the converter itself , but also to protect the motor . The inverter protects against short circuits and overloads of the motor and should also be able to control the temperature of the motor windings through feedback from the installed temperature sensors.
In short, a frequency converter is a device that is worth investing in for a number of reasons. At the same time, it can be purchased with a number of additional devices that expand the capabilities of frequency converters with a whole range of new functional elements.
TIP: in our offer you will find a number of top SINAMICS frequency converters from SIEMENS. Just choose according to the type of application.
