Handbook of Electrical Engineering

INDUCTION MOTORS 123 Table 5.12. Limits to motor ratings due to system voltage Motor power rating (kW) Appropriate system line v ...

124 HANDBOOK OF ELECTRICAL ENGINEERING Motor power rating relative to the power supply capacity. Fault withstand capacity of th ...

INDUCTION MOTORS 125 The use of graphical methods that consist of a family of curves for different scenarios. The use of nomogr ...

126 HANDBOOK OF ELECTRICAL ENGINEERING Select conventional motors but use special external starting devices, e.g. Korndorfer st ...

INDUCTION MOTORS 127 Figure 5.7 Circuit diagram for an induction motor using a star-delta starter. between 65% and 80%. Table 5. ...

128 HANDBOOK OF ELECTRICAL ENGINEERING Figure 5.8 Circuit diagram for an induction motor using a Korndorfer auto-transformer sta ...

INDUCTION MOTORS 129 5.10.5 Part winding method A special design of motor is used. The stator has two three-phase windings that ...

6 Transformers Transformers 6.1 Operating Principles A single-phase power system transformer consists basically of two windings ...

132 HANDBOOK OF ELECTRICAL ENGINEERING Figure 6.1 Flux paths in the core and windings of an iron cored transformer. Figure 6.2 E ...

TRANSFORMERS 133 what is called the ‘referred’ components. For example if the secondary winding impedanceRs+jXs is referred to a ...

134 HANDBOOK OF ELECTRICAL ENGINEERING Figure 6.4 Winding resistance in percent and X-to-R ratio in per-unit versus the MVA rati ...

TRANSFORMERS 135 6.3 Regulation of a Transformer Regulation is a subject that regularly occurs in power systems. Regulation is a ...

136 HANDBOOK OF ELECTRICAL ENGINEERING Figure 6.6 Commonly used primary and secondary winding connections for three-phase transf ...

TRANSFORMERS 137 Table 6.1. Letters used to identify three- phase windings Geographical area Letters and numbers used USA L1L2L3 ...

138 HANDBOOK OF ELECTRICAL ENGINEERING Liquid immersed types use various forms of oil and special synthetic liquids. The chlorin ...

TRANSFORMERS 139 AF AIR-FORCED:- Air forced cooling is arranged by using fans and trunking on the outside of the transformer. T ...

140 HANDBOOK OF ELECTRICAL ENGINEERING An alternative design which has the advantage of reduced periodic maintenance of the oil ...

TRANSFORMERS 141 saturated region of the magnetisation curve. The magnetising current required to establish the total flux will ...

142 HANDBOOK OF ELECTRICAL ENGINEERING It can seen that the instantaneous, and short-term root-mean-square, values of the primar ...

7 Switchgear and Motor Control Centres 7.1 Terminology in Common Use The terms ‘switchgear’ and ‘motor control centres’ are used ...