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Speed, load, and alternator control
Published in Raymond F. Gardner, Introduction to Plant Automation and Controls, 2020
For non-electrical loads, mechanical load measurements are required when paralleling engines, such as when using two ship-propulsion diesel engines clutched to drive a single propeller shaft through a double-input gearset. Mechanical loads can be measured using two methods to calculate torque; a speed sensor, coupled with either a strain-gage torque meter or with an angle-of-twist meter.7 In the propulsion-engine application, the electronic engine-load signal could also be used to feather the blades of a controllable-pitch propeller, to maintain a constant engine-power output at any engine speed. When multiple engines are used to drive a common load, it is common practice to set one engine as the master, and the other engines as slaves in a lead-lag arrangement. The master provides the setpoint signals to the slaves as required to produce its predetermined share of load contribution.
Thermal in-plane buckling of concrete-filled steel tubular arches
Published in Amin Heidarpour, Xiao-Ling Zhao, Tubular Structures XVI, 2018
Y. Bouras, E. Torres-Don, Z. Vrcelj
The lowest load levels were selected to restrict the arches to the elastic domain prior to heating. Subsequently, tests were performed at higher load levels though not at values causing plastic deformations in the steel tube. No influence of the uniformly distributed radial load level on failure mode is evident. Increasing the mechanical load level simply reduces the time to failure.
The thermal-mechanical buckling and postbuckling design of composite laminated plate using a ROM-driven optimization method
Published in Mechanics of Advanced Materials and Structures, 2023
Ke Liang, Zheng Li, Zhenghu Wang, Yongjie Zhang
In this work, the nonlinear equilibrium equations need to be established to solve the geometrically nonlinear response of thermal-mechanical buckling problems, where f is the internal force vector, and where λ denotes the increment of the mechanical load. The thermal load p is predefined to be constant during the imposing of mechanical load. The displacement vector q has N unknown quantities, where N denotes the number of degrees of freedom in the full-scale finite element model. The thermoelastic geometrically nonlinear response is calculated by the Newton-Raphson incremental-iterative method. The repeated solution of full-scale FE model is computationally expansive, even for the modern computers.
Accelerating Time–Current Curve Computation of Induction Motor from Manufacturer Data
Published in IETE Journal of Research, 2021
In order to compute the ATC curve, the accelerating time of induction motor is needed. The acceleration time can be determined from the dynamic motion equation [35] as, denotes a per-unit speed, a ratio between the rotor and synchronous speed. The acceleration torque () is represented by a difference between electrical () and mechanical load () torques as,
Performance assessment of variable frequency drives in heating, ventilation, and air-conditioning systems
Published in Science and Technology for the Built Environment, 2018
Because the motor output mechanical load for centrifugal fan, pump, and compressor applications varies as the cube power of motor speed ratio, which is approximately proportional to the VFD output frequency, the significant motor load and power reduction can be achieved under partial loads. Energy savings of 50% or more were observed when constant speed systems were modified to allow the motor speed to match variable load requirements (DOE 2008). In addition to the energy savings at partial frequencies, the VFD reduces the phase angle between the voltage and current and consequently improves power factor (PF) (Carrier 2005).