Rotational speed

About: Rotational speed is a research topic. Over the lifetime, 23327 publications have been published within this topic receiving 151696 citations. The topic is also known as: speed of revolution & revolution rate.

Melt electrospinning onto cylinders: effects of rotational velocity and collector diameter on morphology of tubular structures

Abstract: Melt electrospinning writing is a direct-writing additive manufacturing process that involves depositing a continuous, viscous and electrohydrodynamically stabilised molten jet onto a collector. Here, molten threads of medical-grade polycaprolactone (PCL) are directed towards stationary/rotating cylindrical collectors (0–6600 rpm), including very slow revolutions well below the critical translation speed (approximately 600 mm min−1) of the molten jet. In this slow-rotation region, the speed of the jet is faster than the movement of the collector and buckled/coiled fibres are produced due to compressive viscoelastic forces. The results are porous PCL tubes with wall morphologies often associated with viscoelastic liquids impinging onto a surface. The curvature of the collector affects how the fibre is deposited, with preferential fibre deposition along the axis of the cylinder. When the collector rotation speed is increased to greater than the speed of the jet, then straight fibres are produced. Such tubular structures have applications in tissue engineering. © 2015 Society of Chemical Industry

Analysis of counter-rotating wind turbines

Abstract: This paper presents a study on the performance of a wind turbine with two counter- rotating (CRWT) rotors. The characteristics of the two counter-rotating rotors are on a 3- bladed Nordtank 500 kW rotor. The analysis has been carried out by using an Actuator Line technique implemented in the Navier-Stokes code EllipSys3D. The analysis shows that the Annual Energy Production can be increased to about 43.5 %, as compared to a wind turbine with a single rotor. In order to determine the optimal settings of the CRWT turbine, parameters such as distance between two rotors and rotational speed have been studied.

Modelling and control strategy of PMSG based variable speed wind energy conversion system

Abstract: With the advance of power electronic technology, novel control strategies and new circuit topologies direct driven permanent magnet synchronous generators (PMSG) have increasingly drawn interests to wind turbine manufactures. In the proposed wind energy system, a PMSG is used as a variable speed generator. The generator model is established in the synchronous-rotating dq reference frame. The torque of PMSG is suitably controlled according to a generator speed and thus the power from a wind turbine settles down on the maximum power point by the proposed MPPT control without a wind speed detector. The speed control is realized through field orientation where the q-axis current is used to control the rotational speed of the generator according to the variation of wind speed and the d-axis current is set to zero. Active and reactive power can be controlled by direct and quadrature current components, respectively.

Method and apparatus for driving and controlling synchronous motor using permanent magnets as its field system

Abstract: A method and an apparatus for driving and controlling a synchronous motor using permanent magnets as its field system are herein disclosed. When a rotational speed of the synchronous motor using the permanent magnets as the field system is more than a base rotational speed, a current condition computing section computes a field weakening reference current in accordance with a battery voltage, a reference torque and a rotational speed. An inverter performs the field weakening control of the the synchronous motor using the permanent magnets as the field system in accordance with the field weakening reference current sent from the current condition computing section to prevent the deterioration of efficiency and the deficiency of output due to the excessive or insufficient field weakening current. The current condition computing section determines optimum reference current by the use of a converged battery voltage, when the battery voltage is converged to a constant value after initial control.

Dual-input infinite-speed integral motor and transmission device.

Abstract: A combination electric motor and transmission unit (1) device has two inputs (2, 3) and a rotational mechanical output (10) at least one of the inputs being of electrical power, to a corresponding integral combination of an electric motor means with a transmission means. The directions of rotation and the rotational speeds of the two inputs can be controlled to provide the mechanical output at any desired rotational speed with peak power output, depending on the controls, thus providing an ideal infinite speed device. The device employs a novel arrangement of a differential unit (24, 42, 41) or a planetary gear unit (27, 36, 46). The combined motor and transmission device is lightweight, requires a small number of moving parts, and is useful in vehicles powered by electricity, including for regenerative braking. Another embodiment of the drive device is useful for a flywheel for peak power supplementation and also regeneration.