Electric torque

Rotor speed control is an integral part of the process of rate of temperature rise. The modem mixer is generally supplied with variable speed, constant torque electric motors driving via gear reducers or by a hydraulic drive system which has a motor shaft mounted tachometer to control rotor speed. Systems that can monitor, adjust and record the mixer rotor speed provide improvement in resultant compound uniformity. Changes in rotor speed within a cycle can be programmed. 

The apparatus is shown in Fig. 4.1. The body of the extraction vessel is made from Pyrex. Separation is effected by absorption of a batch containing both phases into a porous 2 cm diameter nickel-chrome alloy disc (A), the upper surface of which is domed. The disc is mounted on the end of a stainless-steel shaft (B) turned by a geared high-torque electric motor. The disc-shaft-motor assembly can he transported along its axis of rotation to any of three stations. The assembly is shown at its bottom station, with the porous disc within the inner vessel (C), around which is a collar (D) forming the first annular pocket (E). The collar itself forms the inner wall of the second annular pocket (F), the outer wall of which extends upwards to support a Perspex Hd (G) on which the rotor (H) is situated. The inner vessel and both annular pockets are fitted with drain valves. A stiff piece of platinum wire is passed through the Hd into the glassware as far as the level of the first annular pocket. 

The high torque electric motor develops more than 100-kW of motive power which is 35-kW more than the previous design for the A-class. The fuel cell is also more efficient. An enhanced hydrogen storage system gives the vehicle a range of 250 miles (400-kM). The Ballard fuel cells are expected to last at least 5,000 hours in a car and 10,000 hours in a bus. 

Hydraulic motors instead of high-torque electrical motors—this system uses high-pressure hydraulic oil to mn agitators in reactors with very viscous materials which may need electrical motors of much higher rating. 

The 170 hp and 250 Nm maximum torque electric motor provides a top speed of 145 km/h and acceleration from 0 to 100 km/h in 9 s. The lithium-ion batteries promise an all-electric range of 160 km (ETP72 cycle range is calculated to be 240 km), and the ECOPRO system allows setting the onboard systems to optimize consumption with a... 

Figure 9.8 High-torque electric motors can be used as actuators...

Some control valves use high-torque electric motors as their actuator (see Figure 9-8). If the motors are properly sized and their control circuits are maintained, this type of actuator can provide reliable, positive control over the full range of travel. 

If the pump manufacturer uses motors for pump power measurement, these motors ate caUbrated to determine the horsepower from the electric power reading and caUbration curves. Such test motors ate recaUbrated periodically, ensuring the same degree of accuracy as shown by the torque meters. 

Various coupling designs are available to transmit torque from the driver, eg, electric motor, to a pump. In order to contain the pumped fluid inside the pump and prevent the pumpage from leaking, several types of sealing methods are used. A few options are described herein. 

The use of wind as a renewable energy source involves the conversion of power contained in moving air masses to rotating shaft power. These air masses represent the complex circulation of winds near the surface of Earth caused by Earth s rotation and by convective heating from the sun. The actual conversion process utilizes basic aerodynamic forces, ie, lift or drag, to produce a net positive torque on a rotating shaft, resulting in the production of mechanical power, which can then be used directly or converted to electrical power. 

Control of wound-rotor motors, as discussed, can be effected by adjusting the external secondaiy (rotor) resistance either in steps or continuously by liquid rheostat (this method is seldom used). Commonly when secondaiy resistance is varied to adjust speed or torque or to control acceleration, multiple resistance steps are used. These steps may be switched manually (typically a drum switch) or electrically by contac tor. 

Judicious electrical design will ensure a pull-out torque slip as close to the full-load slip as possible and minimize the additional slip losses in such a condition. See Figure 1.8. A motor with a pull-out torque as close to full load slip as possible would also be able to meet a momentarily enhanced load torque during a contingency without any injurious heat or a stalling condition. 

This expression, except for the mechanical design, is totally independent of the type of start and the electrical design of the motor. Electrically also, this is demonstrated in I he subsequent example. The expression, however, does not hold good for an ON-LOAD start. On load, the accelerating torque diminishes substantially with the type of load and the method of start, as can be seen from Figure 2.14, and so diminishes the denominator of equation (2.5), raising the time of start. 

Figure 6.58 Obtaining d.c. voltage through a bridge rectifier Figure 6.59 Braking torque during d.c. electric braking...

Induction motor electrical considerations. When motor starting is desired, the startup torque requirements generally dietate the motor design. The eleetrie eunent inrush at startup is signifieant. The plant eleetrieal grid must be analyzed for eompatibility. 

Steady transmitted torque. Smooth nonfluctuating torque in electric motors, turbines, and a variety of smooth torque-absorbing load (driven) machines. 

The driver is a prime mover capable of developing the required torque at a constant speed or over a range of speeds. The driver s energy source can be either electrical or mechanical. Electrical energy is used by motors, either of the induction or synchronous type, while the mechanical covers a multitude of sources. It may be a fuel, as in internal or external combustion engines, or it may be a gas, such as steam or process gas used in a turbine or expander. 

Semiconductor control modules gate the thyristors, which switch cm rent to the motor field at the optimum motor speed and precise phase angle. This assures synchronizing with minimum system disturbance. On pull-out, the discharge resistor is reapplied and excitation is removed k> provide protection to the rotor winding, shaft, and external electrical system. The control resynchronizes the motor after the cause of pull-out i.n removed, if sufficient torque is available. The field is automatically applied if the motor synchronizes on reluctance torque. The control is calibrated at the factory and no field adjustment is required. The opti-... 

One of the critical measurements is torque or shaft power. A variety of methods is recognized direct methods such as torque meters or reaction mounted drivers (dynamometers) and indirect methods such as electrical power input to drive motors, heat balance, or heat input to a loop cooler. See Part 7, Measurement of Shaft Power, PTC 19.7 1961 [3] for additional information. 

Electro-osmosis has been defined in the literature in many indirect ways, but the simplest definition comes from the Oxford English Dictionary, which defines it as the effect of an external electric held on a system undergoing osmosis or reverse osmosis. Electro-osmosis is not a well-understood phenomenon, and this especially apphes to polar non-ionic solutions. Recent hterature and many standard text and reference books present a rather confused picture, and some imply directly or indirectly that it cannot take place in uniform electric fields [31-35]. This assumption is perhaps based on the fact that the interaction of an external electric held on a polar molecule can produce only a net torque, but no net force. This therefore appears to be an ideal problem for molecular simulation to address, and we will describe here how molecular simulation has helped to understand this phenomenon [26]. Electro-osmosis has many important applications in both the hfe and physical sciences, including processes as diverse as water desahnation, soil purification, and drug delivery. 

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