摘要：Considering the problem of energy saving at industrial enterprises, attention should be paid to the fact that about 70 ... 80% of all electric motors are asynchronous, and most of them are installed in unregulated drives. Most of these electric drives are equipped with asynchronous electric motors with a squirrel-cage rotor (AM SC). Energy saving problem in such cases can be solved by using a frequency converter (FC), however, all FC models are intended for AM SCs, while until the mid-90s the most common variable AC drives were electric drives equipped by an asynchronous motor with a phase rotor (AD PR) as they provided easy speed regulation through the rotor circuit. Such drives are usually used in hoisting and transport machines (conveyors, cranes, etc.). Direct transfer of the abovementioned drives to frequency-controlled mode is quite complicated due to the fact that standard inverters are designed to work with AM SCs having no phase rotor winding, and whose short-circuiting leads to additional electromagnetic losses in comparison with AM SC. An upcoming engineering trend is the development and research of synchronized AM control systems.
