Experts in advanced refrigeration and air-conditioning

Frequency inverter

Given the great importance of electric motors in the daily life of homes and businesses, understanding the role of a frequency inverter is essential to tackle tasks such as energy saving or the search for maximum energy efficiency.

What is a frequency inverter and what is it used for?

First of all, it is necessary to define what a frequency inverter is and what it is used for. Frequency inverters (also called converters) are systems located between electric motors and their power supply, and whose main function is to regulate the rotational speed of the motor and thus the level of energy it is consuming. It does in fact work as a variable frequency drive for the motor and thus ensures that the motor only receives the amount of power it requires.

An inverter can drive motors, compressor motors and industrial motors. It is necessary to know that an inverter can control speed, torque, direction of rotation and power consumption by using external controllers that send a signal to increase or decrease the speed of the motor.

How does a frequency inverter work?

A frequency inverter is based on the characteristics of a given network connected to an electric motor. The frequency inverter is responsible for controlling the speed of a motor. It does this by converting the alternating current of an electrical system into direct current. The rectifier is used for this, something which will be discussed later. Capacitors are involved in the next step. These are the elements that are charged with the DC current that is converted by the rectifier and make the waveform “smoother”.

Finally, there is the inverter. This part of the frequency inverter is responsible for converting the direct current back to alternating current. This is the point at which an electric motor receives exactly the right amount of power, and at which its needs are adjusted to a suitable voltage and frequency.

Parts of a frequency inverter

The parts of a frequency inverter can be described in the following general terms: firstly, the rectifier circuit, which receives the alternating voltage and converts it into direct current. It uses a diode “bridge rectifier” for this purpose. The second element is the intermediate circuit; this consists of an LC circuit which is responsible for smoothing the rectified voltage and its ripple, and for reducing the creation of possible harmonics in the network.

Next is the inverter: this part is responsible for converting the DC voltage of the intermediate circuit into one with variable frequency and voltage, by using pulses. To achieve this, it uses the IGBT system, which generates the voltage pulses in a controlled manner. Finally, there is the control circuit. This is responsible for switching on and off the IGBTs that generate the variable voltage and frequency pulses. It is in addition responsible for monitoring functions in the system, which include – among others – those related to temperature or voltage.

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