Topic
Critical speed
About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.
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TL;DR: In this paper, the rotor radial position control of a two-pole 30 kW 3000 r/m cage induction machine with an additional four-pole stator winding to produce the radial force on the rotor is analyzed.
Abstract: This paper presents a control method for the rotor radial position control of a two-pole 30 kW 3000 r/m cage induction machine that has an additional four-pole stator winding to produce the radial force on the rotor. The controller is used to stabilize the machine, to remove vibration caused by mass-unbalance and rotation, and to produce static force to counter gravity. Both measurement results and finite element computations are shown. In the measurements, the rotor is on a long flexible shaft supported by external bearings. The proposed control strategy allows the machine to run at all operation points (speed, torque) up to the rated values, including at the first critical speed caused by the first natural bending frequency of the rotor shaft. The power consumption of the radial position control and the total effect on efficiency is analyzed. Both rotor eccentricity and the produced four-pole field affect the losses of the machine. The additional power consumption and the total efficiency are presented as a function of the radial force produced.
45 citations
TL;DR: In this paper, a closed-form analytical solution for critical velocity was proposed to calculate the critical velocity of a hypervelocity electromagnetic launch system, which is associated with damaging resonant regimes.
45 citations
TL;DR: In this paper, the nonlinear response of an infinite ice sheet to a moving load in the time domain in two dimensions, using a higher-order spectral method, was calculated, and it was shown that the non-linearity is due to the moving boundary, as well as the non linear term in Bernoulli's equation and the elastic plate equation.
Abstract: We calculate the nonlinear response of an infinite ice sheet to a moving load in the time domain in two dimensions, using a higher-order spectral method. The nonlinearity is due to the moving boundary, as well as the nonlinear term in Bernoulli's equation and the elastic plate equation. We compare the nonlinear solution with the linear solution and with the nonlinear solution found by Parau & Dias (J. Fluid Mech., vol. 460, 2002, pp. 281–305). We find good agreement with both solutions (with the correction of an error in the Parau & Dias 2002 results) in the appropriate regimes. We also derive a solitary wavelike expression for the linear solution – close to but below the critical speed at which the phase speed has a minimum. Our model is carefully validated and used to investigate nonlinear effects. We focus in detail on the solution at a critical speed at which the linear response is infinite, and we show that the nonlinear solution remains bounded. We also establish that the inclusion of nonlinearities leads to significant new behaviour, which is not observed in the linear solution.
45 citations
TL;DR: In this article, a simply supported, rotating Euler-Bernoulli shaft with a single breathing transverse crack is considered, and Galerkin's method and numerical integration of the resulting bilinear equations are used to obtain approximate time histories of the motion.
44 citations
TL;DR: In this article, the effects of the dispersion parameters and the external bounded noise excitation on the vibrational characteristics of the system, such as the critical speed and the vibration amplitude, are investigated.
44 citations