Double-layer Rotor Research Articles

Development of double-layer rotors for asynchronous drives of mining and transport machines

Due to the simplicity of the design and high energy indicators, asynchronous electric motors (AM) are the main consumers in the power supply systems of mining enterprises. Large starting currents of motors lead to heating and damage to the insulation of the stator windings. An urgent problem to improve the reliability of mining and transport machines is the development of AM, providing smooth transients with increased starting torque and reduced starting current. In an AM with a closed-loop rotor, a magnetic conductor is performed by a charged cylinder on the rotor shaft, which is made of electrotechnical steel with high magnetic permeability. The electrical conductor is often a squirrel cage-type short-circuited rotor made of a material with high specific conductivity. A technology has been developed for producing ferro-copper alloys for the active outer cylinder of a double-layer rotor, replacing a "squirrel cage". These alloys combine the properties of an electric current conductor and a magnetic flux. This allows us to obtain the effect of displacement and reduction of current in the rotor, which is accompanied by an increase in the effective resistance of the rotor and the electromagnetic torque during the start-up process. Full-scale experiments have been carried out with asynchronous motors with various rotors having a displacement effect. Motors having double-cage or deep-groove rotors develop an increased starting torque at a relatively lower starting current. The starting quality of these motors is, on average, 1,5 times higher than that of a motor without current displacement. Replacing a double-cage rotor with a double-layer rotor leads to a decrease in the starting current by 25% and an increase in the starting torque by an average of 2,5 times. The quality factor of starting an asynchronous motor with a double-layer rotor is 3-4 times higher than the quality factor of starting similar motors with a conventional rotor cage without current displacement, 2-2,5 times compared with a double cage or a deep groove and 1,3-1,5 times compared with a rotor with a high electrical resistivity. The use of double-layer rotors limits voltage fluctuations in the network, ensures a reliable, smooth start, eliminates vibration and extends the service life of all equipment.

Design and Research on High Power Density Motor of Integrated Motor Drive System for Electric Vehicles

Although many PMSMs are used as the driving source for electric vehicle motor drive systems, there is still a gap compared with the power density index in the DOE roadmap. Considering that the motor occupies a large space in the motor drive system, it is of great significance for the system to increase the motor power density and thus reach the system power density index. This article starts with electrical machine basic design theory and finds the motor power density influence factors. Guided by the theory and considering motor driver influence, this article proposes a high power density motor for electric vehicle integrated motor drive system. The motor for the system is a five-phase interior permanent magnet synchronous motor (IPMSM) with a double-layer rotor structure and fractional slot distributed winding. Compared with Ver1.0 motor, Ver2.0 motor power density improves significantly. In order to prevent damage from excessive temperature, a temperature field solution model is established in this article to compare the cooling effect and pressure loss of the spiral, dial, and axial water jackets. The temperature is checked at motor main operating conditions using an optimal cooling structure. Finally, the power density of the designed Ver2.0 motor reaches 3.12 kW/kg in mass and 15.19 kW/L in volume.

Features of an Asynchronous Motor with a Double-Layer Rotor in Ship Pumping Equipment

This article examines the characteristics and structure an asynchronous motor with a double-layer rotor for ship electric pumping units, as well as approaches to studying it. The main technical requirement for such motors is a low level of noise emission when providing the required heat removal from the operating motor. The use of an external double-layer rotor in this motor makes it possible to significantly improve its working and maintenance characteristics.

Double-layer rotor magnetic shield performance analysis in high temperature superconducting synchronous generators under short circuit fault conditions

High temperature superconducting, HTS, synchronous machines benefit from a rotor magnetic shield in order to protect superconducting coils against asynchronous magnetic fields. This magnetic shield, however, suffers from exerted Lorentz forces generated in light of induced eddy currents during transient conditions, e.g. stator windings short-circuit fault. In addition, to the exerted electromagnetic forces, eddy current losses and the associated effects on the cryogenic system are the other consequences of shielding HTS coils. This study aims at investigating the Rotor Magnetic Shield, RMS, performance in HTS synchronous generators under stator winding short-circuit fault conditions. The induced eddy currents in different circumferential positions of the rotor magnetic shield along with associated Joule heating losses would be studied using 2-D time-stepping Finite Element Analysis, FEA. The investigation of Lorentz forces exerted on the magnetic shield during transient conditions has also been performed in this paper. The obtained results show that double line-to-ground fault is of the most importance among different types of short-circuit faults. It was revealed that when it comes to the design of the rotor magnetic shields, in addition to the eddy current distribution and the associated ohmic losses, two phase-to-ground fault should be taken into account since the produced electromagnetic forces in the time of fault conditions are more severe during double line-to-ground fault.