Rotor eddy current analysis and optimisation design of intermediate ring in novel double squirrel‐cage induction motor

Abstract

The intermediate ring (IR) in the novel squirrel-cage rotor is vulnerable to electrical faults for its relatively small dimension. With the investigation of IR current features, this study mainly proposes an optimisation design strategy of IR to avoid excessive thermal stress at a start-up instant. The amplitude and phase relations of various rotor currents are reflected in the proposed current phasor diagram. In terms of the internal distribution of one concrete current, the circuit analysis theory is applied by dividing the whole conductor into multiple subconductors. The leakage flux around the conductors is simplified, respectively, according to the spatial symmetry. With reference to the existing bar design, the IR design scheme is mainly guided by two essential principles regarding the current-related parameters. Finally, the validity of the designing process of IR is verified by the coupled simulations and temperature-rise experiments. The surface temperature of the designed IR is not the highest, and the partial temperature difference is limited and reasonable.

Analysis of electromagnetic torque for induction motors with a novel non-skewed rotor structure

“…It can be concluded that increasing the axial length of the intermediate ring will not lead to more improved results. In segmented rotor structures with intermediate rings, the axial length is usually selected 1 or 2% of the stack length for optimum performance (Xu et al , 2020).…”

“…By ignoring the magnetic nonlinearity, the stator and rotor MMFs (which contribute to the magnetic field in the air gap) can be separated from each other, assuming that the first is fixed while the second rotates according to the virtual rotor displacement (Pyrhönen et al , 2008). Besides, as mentioned in (Xu et al , 2020), the air gap flux density can be decomposed into fundamental and harmonic components. However, in the case of the fundamental toque-producing air gap flux density, the situation does not vary notably from no-load to the rated torque in most IMs, as experience shows (Boldea and Nasar, 2018).…”

“…Even new skewing patterns could not eliminate the adverse effects of slot skewing. In fact, although novel skew designs have a better torque ripple reduction ability compared with the conventional types, the mean torque drop is more severe in novel designs due to the remarkable decrease in the rotor flux linkage (Wang et al , 2017b; Xu et al , 2017, 2020). This average torque reduction could be even more serious in the case of double skewed rotors, as reported in the related articles (−15% with respect to the non-skewed design and up to −10% with respect to the conventional skewed design) (Xu et al , 2017).…”

Utilization of Two Sensors in Offline Diagnosis of Squirrel-Cage Rotors of Asynchronous Motors

“…The internal shape of the rotor bars and their overall arrangement can also be very varied, e.g., single straight bars, skewed bars, and single or double cage rotors. The shape of arrowed rotor bars with a middle ring is also often found [10,11]. The rotor slots can be open, semi-closed, or fully closed [12][13][14].…”