Metoda wyznaczania rezystancji wirnika z uwzględnieniem wypierania prądu dla silników szybkoobrotowych

High speed motors are supplied with 400-1500Hz frequency voltage. They operate in special conditions and have a structure and properties that differentiate them from classic machines. In particular, they are distinguished by the high frequency of supply voltage, intensive cooling introduced to reduce the size of the motor, and closed rotor slots used to minimize vibrations and noise. In the discussed motors, the closed rotor slot was replaced with an open slot due to saturation of the magnetic circuit by the slot leakage flux. The resistance increase coefficient for rotor cage bar as a function of current flowing through the bar was estimated and then total rotor resistance was determined. Subsequently, the resistance calculated on the basis of geometric dimensions with skin effect taken under consideration was verified against results obtained from measurements. It was proved that short-circuit resistance is not a constant and depends on the value and frequency of current. It also includes a component which derives from additional losses occurring in solid construction elements and in rotor cage bars. The paper also presents descriptions showing changes in short-circuit resistance as a function of the motor's current determined on the basis of measurements with parametrically variable frequency.