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Introduction to Electric Motors
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
There are a few terms to describe rotational motion. Angular speed represents the change in angle per unit of time, typically measured in radians per second (rad/s) in the SI system and in degrees per second in the English system. The rotational speed is the measurement of revolutions per unit of time, expressed as either revolutions per second (Hz) or revolutions per minute (rpm). It is to be noted that speed is a scalar quantity and velocity is a vector. Thus, the difference between angular (or rotational) speed and angular (or rotational) velocity is that the latter contains the information of the rotational direction. Angular speed ω (in rad/s) and rotational speed n (in rpm) can be converted into each other: ω=πn30
Small-scale wind power energy systems for use in agriculture and similar applications
Published in Jochen Bundschuh, Guangnan Chen, D. Chandrasekharam, Janusz Piechocki, Geothermal, Wind and Solar Energy Applications in Agriculture and Aquaculture, 2017
Wojciech Miąskowski, Krzysztof Nalepa, Paweł Pietkiewicz, Janusz Piechocki
If rotor torque increases due to higher wind speed, this increase will be manifested mainly by higher rotational speed. Since torque decreases with a rise in rotational speed, the rotational speed will increase until the rotor torque becomes equal to the load torque. If load torque increases or rotor torque decreases for any reason, the turbine’s rotational speed will be lowered. Since torque increases with a drop in rotational speed, the rotational speed will increase until torque becomes equal to load torque. For this reason, a multi-bladed turbine with a constant torque engine is characterized by stable operation. A multi-bladed turbine will continue to operate when overloaded, but its rotational speed and power coefficient will decrease. In a multi-bladed turbine, axial force from wind is greatest during start-up, and it quickly drops with an increase in rotational speed (KOMEL, 2017).
Introduction
Published in Vaughn Nelson, Innovative Wind Turbines, 2019
The force of the wind (lift and drag) on a blade is applied at some radius from an axis, thus there is a torquetorque on the blade causing it to rotate. The rotational speed is in revolutions per minute (rpm) or angular velocity (ω, radians/second). The power is equal to the torque times rotational angular velocity, P = Tω.
A new method for measuring the static and dynamic fabric/garment drape using 3D printed mannequin
Published in The Journal of The Textile Institute, 2022
Marwa Issa, Sherwet Elgholmy, Aida Sheta, M. Nashat Fors
Figure 4 shows the illustration of a cloth drapemeter. It consists of a circular disk (3) of 18 cm in diameter, attached to a separate shaft (5), and holding a circular fabric (4) of 36 cm in diameter. The disk shaft is attached to the main rotating shaft (7) when the fabric drape test is performed. On the other hand, the 3D printed mannequin (11) is used whenever the garment drape requires testing. It could be linked to the main shaft (7) using a small disk (13) of a diameter of 7 cm. Furthermore, two bearings (8) are used to support the shaft, avoiding movement deflection. The main shaft is connected to a DC motor (15) and its rotation speed could be controlled using the control unit (10). The reflex surface (6) is placed under the disk or mannequin to get a clear shadow formed by the LED light source (16). The reflex surface height could be adjusted to get clear photos. A digital camera (2) is set above the device at three different levels of heights, to adjust to the right one. A computer (14) is connected to the digital camera to analyze the obtained images using image processing.
Micro-end milling of biomedical Tz54 magnesium alloy produced through powder metallurgy
Published in Machining Science and Technology, 2020
Ali Erçetin, Kubilay Aslantas, Özgür Özgün
In micro-milling experiments, the cutting speed, feed per tooth and depth of cut were taken as variable to determine the effect of cutting parameters. The edge radius of the cutting tool was taken into consideration for the feed per tooth values used in the experiments. The cutting tests were performed for three different experimental series (Table 3). In the first series experiments, 10 different feed per tooth values were taken into account for the constant cutting speed and depth of cut. Therefore, the effect of both minimum chip thickness and feed per tooth on burr formation was determined. In the second series of the experiments, the feed per tooth and depth of cut are constant. The effect of the cutting speed on the burr width was determined. In the third series of the experiments, the effect of depth of cut on burr width was determined. For the cutting tests, an experimental setup was used which was designed to perform high speed and high precision cutting (Figure 4). The test apparatus is decorated with a horizontal, three-axis machining center. The maximum rotational speed of the spindle used is 60,000 rev/min. The precision of the axes used in the test apparatus is 0.1 µm and the repeatability accuracy is 0.4 µm. The radial deflection of the cutting tool was measured as 2 µm. Tests for cutting force were repeated at least three times and the results obtained were the average of these three tests.
Frictional performance evaluation of sliding surfaces lubricated by zinc-oxide nano-additives
Published in Surface Engineering, 2020
Ahmed Elagouz, Mohamed Kamal Ahmed Ali, Hou Xianjun, Mohamed A. A. Abdelkareem, Mohamed A. Hassan
The sliding-based-tribotest bench of a piston ring/cylinder liner assembly was used to mimic the reciprocating action of the internal combustion engines in accordance with ASTM G181-11 [27]. A detailed full structural diagram of the sliding-based-tribometer is shown in Figure 4, and was used to study the friction/wear behaviour with ZnO nano-additives. In the tribometer, the friction force was measured during the testing time using a piezoelectric force sensor (Type: LDCZL-ZY, Serial No: LD146040834, Sensitivity of 1.8 mV/V/N). The frictional force signal was amplified by the AMP03 amplifier and the signal was received and processed by a data acquisition interface using the DEWE Soft 6.6.7 platform. The sliding speed was controlled by a 1.5 kW AC motor integrated with a rotational speed controller. The rotational speed was measured by a digital tachometer (HT-4200). The normal force was applied vertically (Z-axis) on the piston ring specimen.