Types of Frequency Converters for Controlling Electric Motors
Frequency converters are important devices for correcting and controlling electric motors, regardless of the type of power supply voltage. Currently, there are three main categories of frequency converters that differ in the number of phases and the connection of power terminals:
- 3-phase input type / 3 output phases
- 1-phase input type / 3 output phases
- 1-phase input type / 1 output phase
Three-Phase Frequency Converter
Currently, three-phase frequency converters are the most common. This is a highly functional device that regulates all main parameters of electric motors. Thanks to them, optimal operating modes for the drive system can be selected without stopping the technological process. The power supply voltage is 380 V. Frequency converters operate with low ripple amplitude and have a minimal harmonic coefficient. Electric motors with three-phase frequency converters are connected in a "Y" (star) configuration. The power of such units significantly exceeds the characteristics of single-phase motors, allowing them to be operated at powers of up to several hundred kilowatts. The increased level of protection makes them indispensable in modern manufacturing.
Single-Phase Frequency Converter
Frequency converters with single-phase power supply are used mainly in the non-industrial sector, where there is no possibility of connection to a three-phase network. They are also known as single-phase frequency converters, although this is not entirely accurate, as they provide three phases at the output, which are used in three-phase electric motors with windings in the form of a "triangle." The power consumption of such devices can reach 2 kilowatts or more.
Frequency Converter for Single-Phase Drive Units
This category of single-phase converters is small and has appeared recently. They are used in residential and public buildings to control the rotation frequency of fans and pumps with single-phase capacitor-type motors. Such electric motors are less efficient than three-phase motors, but in combination with a specialized single-phase frequency converter, they can create reliable and efficient control systems for the specified applications. Compared to the previous category of frequency converters, these devices have only one input and one output phase.