Terminal boxes

These are an itnprovised version of a totally enclosed motor to protect its live parts from ingress of water, rain, snow or airborne particles etc. This is achieved by providing them with additional protection such as labyrinths at joints such as bearing end covers, centrifugal discs, end shields and terminal box and giving the outer... 

All components such as stator housing, end shields, terminal box and covers etc. are pressure tested before use. 

It is recommended that the motor should have separate terminal boxes for the main supply and for the accessories such as space heaters, embedded teinpertiture detectors, bearing temperature indicators and moisture detector terminals, etc. In LT motors, however, if it is not possible to provide a separate terminal box for these accessories, the main terminal box may be adequately spaced to segregate the.se terminals from the main terminals within the box. 

In HT motors, however, these tenninal boxes are always separate because two or more voltages (main and auxiliary). For main terminals there are normally two terminal boxes - one on one side of the stator to house the main three-phase stator teiminals and the second on the other side to form the star point. These boxes are generally interchangeable to facilitate cable routing. 

It may he necessary to separate the live phases within the terminal box to eliminate any occurrence of a flashover or a shon-circuit and a subsequent explosion.. Such explosions may be very severe, depending upon the short-circtiii level of the system and the surrounding atmosphere and... 

The terminal boxes uplo a (aull level of 350 MVA for 5 cycles at 6.6 kV are generalty non-segregated and beyond 350 MVA segregated type. 

HT motors must be provided with phase-segregated terminal boxes as illustrated in Figure 7.17. 

In HT motors the terminal box for space heaters and embedded temperature detectors must be separate from the main terminal box. 

The terminal box must be capable of withstanding the system fault current for at least 0.25 second. 

The terminal box must be suitable for being turned through 180°, for bottom or top cable entry. 

The terminal box must have the same degree of protection as the motor. 

For large motors, 1000 kW and above, if they are provided with star windings the three neutral end leads must be connected to a separate terminal box to enable mounting of CTs for differential protection. The neutral terminal box need not be phase segregated. 

Figure 10.4 Connection of cables in motor terminal box through cable lugs...

While connecting a delta-wound motor through a Y A starter, the metallic shorting links should be removed. Otherwise the starter will have a dead short-circuit at the motor terminal box and may burn the starter, damage the motor terminal box and even line cables. 

The terminal box for its correct position 4 The tei niinal box for proper connections, number of terminals and their markings. 5 The correct dii ection of rotation of the cooling fans... 

Monitoring should include the usual parameters worthy of surveillance in high-speed turbo machinery the temperature of journal bearings, vibration and axial position of the pinions, inlet and discharge temperatures combined with discharge pressure from the individual compressor stages, and various lube oil system devices. Competent manufacturers make sure all measurement locations are completely prewired on the machine and made available at predefined interfaces or in terminal boxes for connection at the plant site. 

All wiring shall be completely enclosed in conduit or suitable boxes. Furnished wiring shall terminate in enclosed terminal boxes. 

When located at the motor the capacitor bank will be normally cabled from the motor terminal box, so that the size of the motor cable can then be selected on the basis of the reduced-power factor corrected current drawn by... 

Figure 10.1. The membrane topology proposed for D. vulgaris Hildenborough DcrH based on hydrophathy analysis and sequence homologies to other bacterial chemoreceptors (Deckers and Voordouw 1996). Shaded boxes, putative membrane-spanning (residues 9-30 and 422 31), excitation (residues 653-692), and methylation (residues 757-764) regions. The C-terminal box (residues 824-959) indicates the Hr-like region. Reprinted with permission from Xiong et al. (2000), copyright 2000 American Chemical Society.

Fig. 5.2 Spatial orientation of secondary structure of AspAT exons. The shaded JV-terminal box indicates the presequence region PP, prepiece. Locations of introns are denoted by vertical lines and the exon/ intron boundary amino acid residues are indicated in one-letter code. The numbering of the residues corresponds to those in pig cAspAT. a-Helices are represented by open boxes and /3-sheets by black boxes. The domains of the proteins are also indicated A. A -terminal Small, small domain Large, large domain. Results reproduced from Juretic et al.I2)...

The motor shaft is usually held in place by two insulated slide bearings equipped with ring lubrication. In addition, the bearings are cooled for example by an oil-water cooling system. The terminal box of the motor should be so dimensioned as to accommodate the current transformers for differential protection of the motor. To prevent the formation of condensation in the motor during standstill, a space heater is installed. 

The connection terminals required for power input and the control processes are housed in a high pressure proof terminal box constructed for the corresponding pressure rating (Figure 5). 

Pressure is at normal atmospheric in the stator compartment, and so there is no particular load on the cable terminal box. However, it is specified on the assumption that it may have to withstand the system pressure and the discharge pressure of the pump and provide sealing in relation to the outside environment. This is a safety precaution to prevent any escape of fluid from the motor in the event of damage to the can, e g. in the form of corrosion or abrasion. In most applications, high-pressure canned-motor... 

Type(s) of protection (abbreviations only, see Table 5.1). The dominant/main type of protection, followed by auxiliary types of protection, e.g. a flameproof motor with an e -type terminal box de, or a pressurized motor with an e -type terminal box and flameproof standstill heaters ped... 

Electrical apparatus with combined non-intrinsically safe and intrinsically safe components, e.g. a flameproof enclosure with a power supply for intrinsically safe circuits, with a 690 V input, terminal boxes in increased safety, is considered as an associated apparatus (from the intrinsic point of view). In this case, the abbreviation for intrinsic safety is put in brackets ... 

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