Motors types

This is a location safer than Zone I with a likelihood of concentration of explosive gases, chemical vapour or volatile liquids during processing, storage or handling. This would become a fire hazard only under abnormal conditions, such as a leakage or a burst of joints or pipelines etc. Such a condition may exist only for a short period. A standard motor with additional features, as di.scussed below, may also be safe for such locations. A non-sparking type. Ex. n , or an increased safety motor, type Ex. e , may also be chosen for such locations. 

Special provisions are laid down in lEC 60079-0 and lEC 60079-1 for motors required for such locations in view of fluctuating degrees of humidity and temperature. Such locations are defined with a surface temperature limit of 150°C where coal dust can form a layer, or 450°C where it is not expected to form a layer. Otherwise, other details are generally the same as for flameproof motors type Ex d , according to lEC 60079-1. For variations in length of paths, gaps, widths, creepage and clearance distances, the reader should consult these Standards. 

Electrical apparatus for explosive gas atmospheres Increased safely motors, type e . General requirements 6381/1991 BS. 5501-6/1977 BS 5000-15/1985 ... 

Water-Cooled motors, type CACW (cooling type ICW 37 A 81 or ICW 37A 91) (Section 1.16, Table 1.12) should be fitted with moisture detectors to provide an audio-visual alarm in the event of a leakage in the water circuit or a higher coolant temperature. 

Eleetrie motor type, eurrent eonditions, power faetor, enelosure, serviee faetor, temperature rise, ambient temperature. 

A rule of thumb that was used in the past for constant speed applications wii.s to consider the selection of a synchronous motor where the application horsepower was larger than the speed. This, of course, was only an approximation and tended to favor the selection of a synchronous motor and would be considered too severe by current standards. However, the rule can aid in the selection of the motor type by giving some insight as to when the synchronous might be chosen. For example, applications ol several hp per rpm often offer a distinct advantage of the synchronous over the induction motor. In fact, at the lowest speeds, larger sizes and highest hp/rpm ratios may be the only choice. 

Electric Motors, 615 Terminology, 615 Load Characteristics, 616 Basic Motor Types Synchronous and Induction, 616 Selection of Synchronous Motor Speeds, 619 Duty, 625 Types of Electrical Current, 625 Characteristics, 627 ... 

There are a number of electric motor types available. These motors are classified by the National Electrical Manufacturers Association (NEMA). These electric motor classifications are presented in the NEMA standards [7]. 

Motor end plate. Here the ACh receptors are of the motor type (p.182). 

Central nervous system (CNS A, top). NAChR are involved in various functions. They have a predominantly presynaptic location and promote transmitter release from innervated axon terminals by means of depolarization. Together with ganglionic NAChR they belong to the neuronal type, which differs from the motor type in terms of the composition of its five subunits. 

Figure 6.87 Longitudinal section drawing of a cage induction motor with identical frame number (132) to that shown in Fig. 6.86 flameproof motor. Type of protection EEx de IIC T4 (terminal box in e ).

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