Electrical installation electric motors

Within these basic principles there are many types of electric motors. Each has its own individual operating characteristics peculiarly suited to specific drive applications. Equations (29-1) through (29-9), presented in Table 29-1, describe the general operating characteristics of alternating-current motors. When several types are suitable, selection is based on initial installed cost and operating costs (including maintenance and consideration of rehability). 

Economics Power-recoveiy units have no operating costs in essence, the energy is available free. Furthermore, there is no incremental capital cost for energy supply. Incremental installed energy-system costs for a steam-turbine driver and supply system amount to about 800 per kilowatt, and the incremental cost of an electric-motor driver plus supply system is about 80 per kilowatt. By contrast, even the highest-inlet-pressure, largest-flow power-recoveiy machines will seldom have an equipment cost of more than 140 per kilowatt, and costs frequently are as low as 64 per kilowatt. However, at bare driver costs (not including power supply) of 64 to 140 per kilowatt for the power-recovery driver versus about 30 to 80 per Idlowatt for... 

One can adopt a suitable procedure of installation, grouting, type of foundation and alignment etc., depending upon the size of motor, the duty it has to perform and the location of the installation (such as hazardous or seismic, etc.). Here we discuss briefly only the important aspects of installation and maintenance of electric motors. 

The relubricating period obtained from this expression is valid for operations up to 70°C, when measured at the outer ring. This interval should be halved for every 15°C rise in temperature above 70°C, which is unlikely to occur in an electric motor. For operating in areas that are hazardous or contaminated which may affect the life of the grease, the regreasing interval may be reduced, depending upon the installation s environment. 

Installation of bearings and pulleys Important checks at the time of commissioning Maintenance of electric motors and their checks Maintenance of bearings General problems in electric motors and their remedy Winding temperature measurement at site Analysis of insulation failures of an HT motor at a thermal power station... 

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. 

Space heaters, particularly in electrical motors and generators which may be idle for significant periods of time, can also help prevent the accumulation of moisture. Space heaters installed in classified areas must operate at temperatures below high temperature devices. 

MG 2 Safety Standard for Construction and Guide for Selection, Installation, and Use of Electric Motors and Generators MG 10 Energy Guide for Selection and Use of Polyphase Motors VE 1 Cable Tray Systems... 

Figure 10-175 illustrates the assembly of a typical forced draft unit with electric motor and gear drive. Note that walkways and access ladders are necessary to reach the exchanger connections where valves are usually installed. If... 

The centrifugal compressor is well established for the compression of gases and vapors. It has proven its economy and uniqueness in many applications, particularly in which large volumes are handled at medium pressures. This compressor is particularly adaptable to steam turbine or other continuous speed change drives, as the two principles of operation and control are quite compatible. It is also adaptable to the electric motor, gas engine, and gas turbine with each installation being specific to a particular problem or process. Installation as well as operating costs can be quite reasonable. 

Insufficient ventilation shortens the life of the electric motor. In installations where the intake air is drawn from the compressor room, poor ventilation may also damage the compressor, as the temperature of the discharge air... 

Most mixers are driven by electric motors, or in some cases by mechanical turbines, with gears ratioed to give the proper performance speed of the impeller. A variable or 2-speed driver or gear system often proves worth the extra cost, since it is difficult to predict the exact speed requirements for some new installations. This is particu-... 

The use of traditional rod and piston pumps continues at many LNAPL recovery locations, particularly at refineries and distribution terminals. These units are usually powered by single-speed electric motors and have adjustable stroke lengths to control the pumping rate. When installed with the intakes set at the optimum pumping depth, they function fairly well. The primary advantage of rod and piston pumps is that the smooth slow stroke rate can pump mixtures of product and water without creating a significant emulsion. 

Electric installations should be hermetically sealed and non-sparking. The bulbs should be enclosed in safety shields. Electric motors should not be installed in premises in which powder is manufactured. 

Electric Equipment in Explosion-Exposed Installations. This equipment includes electric motors, switches, wiring, etc. They must be of fireproof type. The discussion on this subject is in the following refs ... 

In the smaller cooling tower installations employed for refrigeration and air conditioning service, induced-draft propeller-type air movers are used. A favored design utilizes the rotary centrifugal squirrel cage blower, which is normally driven by electric motors connected to the rotors by V-belts. Because of lower fan efficiency, these often use more electric power to achieve the same results as propeller fans. 

The injection point of the sulfuric acid is in the pump bay, or as near as possible to water intake. The sulfuric acid pump is normally a motor-driven proportioning pump, and an electric motor is connected to a pH analyzer installed on the cooling water supply header so that the pump starts and stops, depending on the pH in the circulating water. Table 8.2 summarizes various chemical treating agents for cooling water towers. 

Electric motor drives are preferred if the power cost is low, since electric packages are less costly than turbine drives, and motors generally have lower maintenance requirements. Turbine drives are preferred if the fuel gas cost is more attractive than the cost of electric power. Turbines can also provide process heat for the pre-treatment system and may, thus, reduce the need for heating equipment. In many installations, gas turbine fuel is provided from flash gas in the main process. 

In this the refrigerant vapor is compressed mechanically. Two-stage motor compressors are used mostly in freeze-drying systems. This compressor is installed in a screwed-on housing together with an electric motor. 

Materials used must cleaned and disinfected with the usual cleaning and disinfecting agents. Friction in the transport system must not cause particles. Electric motors without ventilators must be used and the sensors installed must be resistant to the cleaning and disinfecting agents. In general, every process must be reproducible, documented and validated. 

The following table lists some common laboratory devices along with the current and power requirements for the operation of the device.1 This information is important to consider when instrumentation is being installed, relocated, or used on the same circuit. Common 120-V circuits in laboratories are typically rated at 10 or 15 A. Note that the current draw often spikes to a high level in first few microseconds after a device is energized. This is especially true for devices that have electric motors. 

Mechanical stirring is recommended for testing polymerization reactions or viscous reaction mixtures. This requires the use of taller containment vessels than the original to install the electric motor for the agitator. 

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