Loss analysis in the case of a chute
In the case of a chute, if the bar is insulated better, the loss caused by the harmonic phase of the stator phase in the squirrel-cage winding can still be approximated according to equation (1), but in the formula Take K, where K, is the chute coefficient of the squirrel-cage rotor winding versus the vth harmonic. Assuming that the rotor slot is skewed by a stator pitch, the resultant potential induced by the stator magnetomotive tooth harmonics is nearly equal to zero over the length of the entire bar.
P2v=(4m12W12Kdpv2K2v4R2vI12)/Z2........................(1)
In formula (1):
I1 - stator phase current;
R2v - rotor bar AC resistance (corresponding to the relevant harmonic frequency);
Kdpv - the stator winding coefficient for the vth harmonic;
K2v - the winding coefficient of the imaginary rotor winding versus the vth harmonic.
However, in the case of a chute, if there is no good insulation between the bar and the core, the potential induced by the harmonics of the stator magnetism in the rotor cage winding will form a "horizontal" between the adjacent bars through the core silicon steel sheet. "Current, the "lateral" current formed between adjacent "half" bars will create additional losses. The magnitude of this loss is mainly determined by the contact resistance Rc between the bar and the core, in addition to the frequency of the harmonic magnetic field, the magnitude of the magnetic density, etc., but the processing factors affecting the magnitude of the contact resistance Rc are difficult to grasp, and thus It is difficult to determine a general formula for calculating Rc, so that there is currently no mature and simple method for calculating this loss.
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