Special-purpose motors

Selection of a special-purpose motor 7/189 List of formulae used 7/193... 

Special-purpose motors such as increased safety motors, flame-proof or explosion-proof motoi s must be checked for gaps, clearances and creepage distances of all the mating parts forming flame paths. The construction of these motors must follow lEC 60079 as noted in the list of standards. 

Textile motors Crane motors Determining the size of motor Sugar centrifuge motors Motors for deep-well pumps Motors for agricultural application Surface-cooled motors Torque motors or actuator motors Vibration and noise level Service factors Motors for hazardous locations Specification of motors for Zone 0 locations Specification of motors for Zone I locations Motors for Zone 2 locations Motors for mines, collieries and quarries Intrinsically safe circuits, type Ex. f Testing and certifying authorities Additional requirements for ciritical installations Motors for thermal power station auxiliaries Selection of a special-purpose motor... 

A special-purpose motor is a motor with special operating characteristics or special mechanical construction, or both, designed for a particular application and not falling within the definition of a general purpose or definite-purpose motor. 

Special-purpose motors incorporate specialized operating characteristics and/or mechanical construction to serve one-of-a-kind appUcations not satisfied by general- and definite-purpose motors. 

Like a special-purpose electric motor (Chapter 7) a capacitor unit can also be required to perform under special operating conditions, such as ... 

As with the motor driver, the steam turbine must be matched to the compressor. Also, a turbine rating of 110% of the maximum power required by the compressor should be specified. This should be at the compressor s normal speed point. The turbine speed should include a maximum continuous speed 105% of the normal compressor speed. API Standards 611 and 612 cover general purpose and special purpose steam turbines 7, 8]. 

Select special-purpose designs for the motor in which the winding arrangements are modified by external switching devices that are matched to the motor, e.g. star-delta motor and starter. 

This is also known as pressnrisation or continuous dilution. It is mainly applied to large motors, control panels, display panels, and occasionally special purpose generators. Type p protection is suitable for Zone 1 and Zone 2 areas. 

When bringing ordinary electrical equipment such as vacuum cleaners and portable electric drills having series-wound motors into the laboratory for special purposes, take specific precautions to ensure that no flammable vapors are present before such equipment is used (see Chapter 5, section G). 

The potential market is very large. It encompasses applications in all those areas currently served by electric motors and internal combustion engines. Industry sources feel that special purpose... 

The importance of electro-nuclear energy should, however, be considered on the world rather than the national scale, especially when the following points are taken into account the very marked increase in the demand for energy, the increasing cost of classic fuels and the need to use the latter more and more for specialized purposes (chemical, iron and steel industries, motor-vehicle traction, etc.). 

NEMA also classifies electric motors by appUcation as general-purpose, definite-purpose, or special-purpose. A general-purpose motor is an indnction motor which has a continuous rating, service factor, and temperature rise in accordance with NEMA standards. General-purpose motors are built in quantity in standard ratings with standard operating characteristics and mechanical construction for a wide variety of common appUcations. 

In this chapter, we will discuss petroleum products used for energy purposes, that is, motor fuels and heating fuels. Chapter 6 will be devoted to other products such as special gasolines, lubricants, petrochemical bases, and asphalts. 

Whenever the process machine operates at the same speed as its driver, the two can be directly coupled. This direct couphng stiU allows for a variable speed, through acuustments of the speed or the driver. Steam turbine speed can be easily adjusted, and electric motor speed can also be varied by the use of special drives that vaiw the frequency of the power applied to the motor. Wdiether the speed is fixed or variable, direci coupling of two machine shafts presents the problem of accommodation of misalignment. To this purpose, machines are coupled through a.flexible coupling. 

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