• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.11-15
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• 2018

Torque tubes in High Temperature Superconducting (HTS) motor transfer torque from superconducting field winding rotor to the room temperature shaft. It should have minimum heat conduction property for minimizing the load on cryo-refrigerator. Generally, these torque tubes are made with stainless steel material because of high strength, very low outgassing and low thermal contraction properties at cryogenic temperatures and vacuum conditions. With recent developments in composite materials, these torque tubes could be made of composites such as Kevlar and S-Glass, which have the required properties like high strength and low thermal conductivity at cryogenic temperatures, but with a reduced weight. Development and testing of torque tubes made of these composites for HTS motor are taken up at Bharat Heavy Electricals Limited (BHEL), Hyderabad in collaboration with Central Institute of Plastics and Engineering Technology (CIPET), Chennai and Indian Institute of Technology (IIT), Kharagpur. As these materials are subjected to vacuum, it is important to measure their outgassing rates under vacuum conditions before manufacturing prototype torque tubes. The present study focusses on the outgassing characteristics of Kevlar and S-Glass, using an Outgassing Measurement System (OMS), developed at IIT Kharagpur. The OMS facility works under vacuum environment, in which the test samples are exposed to vacuum conditions over a sufficient period of time. The outgassing measurements for the composite samples were obtained using pressure-rise technique. These studies are useful to quantify the outgassing rate of composite materials under vacuum conditions and to suggest them for manufacturing composite torque tubes used in HTS motors.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.1923-1929
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• 2009

The design of SPMSM(surface mounted permanent magnet synchronous motor) has been performed to reduce cogging torque and torque ripples. In general, cogging torque and torque ripples are affected by the shapes of teeth width, yoke depth, magnet pole arc, etc. Particularly, the minimum design point of cogging torque and torque ripples are different so that the design of SPMSM should be done to compromise both of them for precision application. In this paper, the design of PMSM for EPS(electric power steering) system is performed to verify the validity, and the design characteristics versus teeth width, yoke depth, and magnet pole arc are investigated in order to find out the minimum point of cogging torque and torque ripples. In addition, skew of PM is applied for cogging torque reduction.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.4B no.1
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• pp.20-23
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• 2004

BLDCMs are widely used in many industries. In certain specialized areas, they need to have high efficiency, high power rate and produce a low volume of noise, etc. In this study, a new type of slotless BLDCM is proposed that has no cogging torque, low iron loss and low volume as compared to commonly used BLDCMs. With a high performance magnet and coreless compact winding structure similar to those employed in linear synchronous motors, motor volume is reduced. The proposed motor has been put been through various experiments arid has demonstrated acceptable results for industry applications.

• The KSFM Journal of Fluid Machinery
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• v.6 no.3 s.20
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• pp.44-50
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• 2003

An experiment is conducted for measuring the performance of an air tool, which is operated at 100,000 RPM in an unloaded state with very low torque. A 551 kPa in gauge pressure is supply to the inlet of an air tool. An experimental apparatus is developed as a friction type dynamometer. Inlet total pressure, air flow rate, rotational speed and operating force are measured simultaneously. Torque, output power and specific output power are obtained with different rotational speeds. Those are compared with the experimental results which were obtained by a commercial dynamometer. However, no commercial dynamometers are available for measuring the torque above 30,000 RPM. In order to reduce the rotational speed, a reduction gear is applied between the air tool and the commercial dynamometer. Torque and power obtained by the commercial dynamometer show $55\%$ lower than those obtained by the developed friction type dynamometer, because the mass is added to the rotor of air tool for the braking system of the commercial dynamometer and power loss is generated by the reduction gear. From the compared results, the friction type dynamometer should be applied for measuring the performance of the air tool operating at low torque and high RPM.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1956-1964
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• 2018

Since the stator winding of High-Speed Permanent Magnet Generator (HSPMG) has few winding turns and low inductance value, it is more prone to be influenced by harmonic current. Moreover, the operation efficiency and the torque stability of HSPMG will be greatly influenced by harmonic current. Taking a 117 kW, 60 000 rpm HSPMG as an example, in order to analyze the effects of harmonic current on HSPMG in this paper, the 2-D finite element electromagnetic field model of the generator was established and the correctness of the model was verified by testing the generator prototype. Based on the model, the losses and torque of the generator under different frequency harmonic current were studied. The change rules of the losses and torque were found out. Based on the analysis of the influence of the harmonic phase angle on torque ripple, it is found that the torque ripple could be weakened through changing the harmonic phase angle. Through the analysis of eddy current density in rotor, the change mechanism of the rotor eddy current loss was revealed. These conclusions can contribute to reduce harmonic loss, prevent demagnetization fault and optimize torque ripple of HSPMG used in distributed power supply system.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.546-557
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• 2012

In Conventional Combined Vector and Direct Controls (VC-DTC) of induction motor, stator current is very rich in harmonic components. It leads to high torque ripple of induction motor in high and low speed region. To solve this problem, a control method based on the concept of fuzzy logic approach is used. The control scheme proposed uses stator current error as variable. Through the fuzzy logic controller rules, the choice of voltage space vector is optimized and then torque and speed are controlled successfully with a less ripple level in torque response, which improve the system's performance. Simulation results trough MATLAB/SIMULINK${(R)}$ software gave results that justify the claims.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.346-350
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• 2001

PMSM drives are widely used in the industrial and residential applications because of high efficiency, high power density and high performance. For better performance of PMSM, however, torque ripples should be reduced. This paper investigates a reduction of torque ripple due to the unsinusoidal flux linkage produced by the shapes of stator slot and magnetic pole. To minimize torque ripple, a simple flux estimator is proposed. This method interatively compensates the distributed flux linkage from an error between the measured and estimated currents. The proposed algorithm is verified through simulation.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.139-141
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• 2009

This paper presents a design and analysis of torque characteristics of a two-phase SRM(Switched Reluctance Motor) for high speed blower system. To reduce the electrical frequency and core losses at high speed region, In order to reduce torque ripple and torque dead-band, variable rotor air-gap structure is adopted and the air-gap is optimized according to torque production. The optimized torque output is verified by the FEM results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.243-246
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• 2000

Productivty of tapping has been increasing through the tcchnological advances in synchronization between spindle rotation and feed motion even in the high spindle speed. However, not much researches have been conducted about tapping process because its complicate cutting mechanism. In order ta investigate the characteristics of the tapping process, this paper concentrates on the analysis of curting torque behavior during one cycle of lapping. As one completc thread is performed through the whole chamfer ercuttlng, cutting torque increases highly in chamfer cutting, but smaothly in full thread cutting Functioning of the threads guide. Cutting torque in backward cutting is smaller than in Sorwerd cutting due to only friction farce in against between the tool and workpiece. And torque behavior of a periodic Sine ripple-mark was identified during one revolution of a tap.

• Journal of Power Electronics
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• v.9 no.4
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• pp.582-592
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• 2009

This paper proposes a new speed sensorless direct torque and flux controlled interior permanent magnet synchronous motor (IPMSM) drive. Closed-loop control of both the torque and stator flux linkage are achieved by using two proportional-integral (PI) controllers. The reference voltage vectors are generated by a SVM unit. The drive uses an adaptive sliding mode observer for joint stator flux and rotor speed estimation. Global asymptotic stability of the observer is achieved via Lyapunov analysis. At low speeds, the observer is combined with the high frequency signal injection technique for stable operation down to standstill. Hence, the sensorless drive is capable of exhibiting high dynamic and steady-state performances over a wide speed range. The operating range of the direct torque and flux controlled (DTFC) drive is extended into the high speed region by incorporating field weakening. Experimental results confirm the effectiveness of the proposed method.