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Squirrel-cage high-speed motors have found their application among others in grinders for precise
processing of bearing rings. These are two-pole or, more rarely, four-pole squirrel-cage induction motors with
a maximum power of up to 2kW , with closed rotor slots and speeds ranging from 12 to several hundred
rpm. They are supplied with 200 ÷ 2000Hz frequency voltage from motor or thyristor frequency converters.
Closed rotor slots decrease the magnetising current, pulsation losses and losses caused by friction against the
cooling agent; they also decrease motor noise and increase the mechanical strength of the rotor.
Because of the use of closed rotor slots in the rotor and the particular structural dimensions of these machines,
part of the main flux closes over the slot. Superfluous shunted flux is thus created, which does not participate
in inducing voltage in a rotor cage bar. This results in an increase in the value of the scatter flux and decreased
motor power. It is then necessary to take this flux into consideration while analysing the properties of highspeed
induction motors.
This article describes the essence of the formation of a shunted flux and shows the relationships which allow
its calculation. On this basis, the effect of a shunted flux on the parameters of an equivalent scheme of a motor
was established.
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