Electric motors phase

For a three-phase electric motor, the horsepower is calculated as... 

Starting up the turbocompressor installation of a nitric acid plant does not present a problem. As mentioned earlier, during the startup phase the expander is not able to contribute any power. Accordingly, electric motor drivers must initially provide power in excess of the nominal operational rating. 

A relatively new innovation for use in electric motor compressor drives is the variable frequency power source. Fundamentally, the power source converts an existing three-phase source into DC then uses an inverter to convert back to a variable frequency supply. Thyristors or transistors are used to switch the output at the required frequency. 

Frequency converters constructed for use with three-phase motors less than 4 kW can therefore be delivered with a single-phase supply from the electrical mains. For greater power requirements, it is most common to use a three-phase power supply. Through switches and potentiometers or the programming module of the frequency converter, the important parameters of electrical motors can be adjusted as needed. 

Direct drive three-phase electric motor... 

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. 

Alex Zettl and his colleagues at the University of California, Berkeley, have been active in this field. In 2005, Zettl and his team built an oscillator that is one of the smallest electric motors in the world. The motor works by driving some of the atoms of a tiny drop of liquid metal over to an adjacent and smaller drop. An electric current powers this movement. The most interesting phase of the operation occurs during the rebound, as the atoms return to the original source. This phase happens because of a molecular force known as surface tension. 

There are two general types of steam turbines extraction and condensing. The most common turbine with which the process operator comes into contact is used to spare an electric-motor-driven centrifugal pump. The three-phase, AC motors used in the United States and South America are either 1800 or 3600 rpm. The motors used in Europe are 1500 or 3000 rpm. Small steam turbines (20 to 500 hp) used to drive centrifugal pumps, are rated for the same speed as the electric motors that are used in that particular service. 

The low power requirement is ideally suited to an electric motor drive, with the standard 440V (50 cycles per second), 3 phase connection. AJAX confirmed this choice, advocating a 2-pole motor of the above characteristics to meet the rotational speed of 2900 rpm. This is advantageous because motors of 4 poles or more greatly increase the unit cost. 

To complete sizing the Karr column requires sizing the electric motor. The size of the electric motor to disperse one of the phases is small. Walas [51] states that a 1.5 hp (1.12 kW) motor is sufficient to agitate a Karr extractor 30 in (0.762... 

The fluid that flows through the coils in the back of a refrigerator removes heat from the interior by the same process. In fact, the refrigerant used in freezers will absorb so much heat that it can freeze skin. The fluid is compressed by the compressor, then allowed to expand through the coils. The compression is driven by an electric motor, and the expansion is driven by entropy the gas phase is a more disordered state than the liquid phase. 

Dense-phase flow properties can be predicted by measuring the viscosity and deaeration rate of a fluidized bed in a laboratory test (117). This method appears to be especially useful for evaluating the flow characteristics in standpipes. The viscosity is measured by means of a Brookfield viscometer, which consists of a cylindrical wire-screen spindle rotated about its axis by an electric motor through a torsion spring. The torque required to rotate the spindle is measured by displacement of the... 

In addition to the above, NEMA designates a special class of Premium Efficiency Electric Motors (2003) for three-phase induction motors applied to municipal or industrial applications for operation on voltages of 600 V or less, rated 500 HP or less, operating more than 2000 hr/yr at more than 75% of full load. For details, please refer to NEMA MG 1-1998 Table 12-12. For each HP rating, that table defines nominal and minimum efficiencies for 2-, 4-, and 6-pole open motors. 

The hydraulic system consists of oil reservoir, electric motor, hydraulic pump, heat exchange for oil cooling, oil filters, oil level indicator, electric valves and flow distributors. An hydraulic plant which has been properly installed and care has been taken during the start-up phase, should enjoy long life and not need much maintenance. 

Energy losses along the well column are smaller for three-phase electric motors than for... 

With DC electric motors, power factor correction is sometimes used to improve the power factor of the drive [30]. This is done by incorporating capacitive components into the circuit. Capacitors produce leading reactive power whereas the phase-controlled rectifiers produce lagging reactive power. Thus, by adding appropriately sized capacitors, the power factor of the drive can be improved. 

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