Rotational machines

In the Agitair Rotation machine (Fig, 19-76), the impeller is a Rat rubber-covered disk with steel Fingers extending downward From the peripheiw, A rubber-covered stabilizer eliminates dead spots in the agitation zone and improves biibble-ore contact. The degree oF aeration is controlled bv regulating air volume on each cell with an individual air v alv e. Air is supplied at 10 x lO Pa (1,5 IbF/iir),... 

One of the oldest adjustable-speed drives is the Ward-Leonard system. This consists of an ac to dc motor-generator set and a shunt or compound-wound dc motor. Speed is adjusted by changing the generator voltage. A functional equivalent of this drive uses an adjustable-voltage rectifier feeding a dc motor. This system has only one rotating machine in contrast to the three of a conventional Ward-Leonard system. 

NEMA/MG-1/1993 NEMA/MG-2/1989 Motor and generators ratings, construction, testing and performance Safety Standards (enclosures) for construction and guide for selection, installation and use of rotating machines ... 

Figure 9.5(b) Approximate temperature coefficient of insulation resistance of rotating machines... 

Rolaling elecU ical machines Raling and performance for rotating machines 4722/1992, 325/1996 BS EN 600,34-1/1995... 

Guide for insulation maintenance of large a.c. rotating machines (10 kVA and larger)... 

Until a few years ago, there was no widely accepted standard for a voltage endurance test of the rotating machines. Different agencies had adopted different practices on different assumptions, pending a final decision by the lEC working committee TC-2 of lEC 60034-15. The committee submitted its report in 1988 and the following test data, which are now universally adopted, are based on this report. 

Measurement and evaluation of vibration severity in-sim oflarge rotating machines 11727/1990 BS 7854-1/1996 I08I6-I/I995... 

Guide for testing turn to turn insulation on form wound. stator coils for a.c. rotating machines. 

Practice for insulation testing. Large a.c. rotating machines w4th high voltage at very low frequency. 

Rhudy, R.G. el al., Impulse voltage strength of AC rotating machines IEEE Trans. PAS. 100, No. 8(1981). 

Figure 12.27 Typical scheme for surge protection of a rotating machine...

One may observe that alt the above. special service conditions are generally the same as I orihe rotating machines discussed in. Section 1.6. 

Bearings and bearing housings in a rotating machine, in view of the very small gap between the stator and the rotor. 

Protection of rotating machines from switching surges 17/578... 

The need to protect a rotating machine from switching surges, contact bouncing and surge transferences 17/576... 

Figure 17.7(a) Surge impedance of rotating machines as a function of inpuf MVA/VUne kV (from Pretorious and Eriksson, 1982)... 

Since the standard insulation level (BIL) of a machine, equipment or a system is already defined, according to Tables 11,6. 14.1, 32.1(A), 13.2 and 13.3. the mtichines are aecordingly designed for this btisic insulation (BIL) only. When the prospective surges are expected to be more severe than this, separate protection becomes imperative. This is particularly important for a rotating machine w hich, besides being a dry equipment, also has only a limited space within the stator slots and hence has the smallest BIL of all, as is evident from Table I 1.6. compared to Tables 14.1, 32.1(A) and 13.2. For its comprehensive protection it can be considered in two parts,... 

I I Insulation Sub-committee. Rotating Machinery Committee. Impulse voltage strength o) AC rotating machines, IEEE Transactions on Power Apparatus and SsKtenis, PAS-100. No. 8, August (1981). 

They offer a relatively higher and may generally not be suitable for protection of equipment that has a low BIL. The BIL of a rotating machine or a dry type transformer, for instance, may fall lower than the... 

---