Scope Richard Crowder

E 3 AN  Electrical  Electronic  Engineering

Numbers…. Students H5: Electrical189 H6: Electronic3218 Source: UCAS 1999 statistics

Spread Microelectronics Generation Students Power

Context  Generation  Control  Utilisation

Question…. Can the study of Electrical and Electronics be treated in isolation of: (i) Each other (ii) Other engineering disciplines A holistic approach is required, which is reflected in e 3 an.

Typical Target Themes  Phase 1  Analogue Electronics  Digital Electronics  Microprocessors  Circuits  Signal Processing  Phase 2  Power Electronics  Semiconductors  Electromagnetism  Control engineering  Real time control systems  Instrumentation

The Question bank must…  Scope  Central to a specific theme  Cross between themes  Design  Emphasize the multidisciplinary nature of the subject.  Be realistic

Variable Speed Drives VSD Control theory EMC & RFI Electromagnetics Networking DSP Power Systems Power electronicsMicroprocessors Mechanics Thermodynamics

Exemplar Question A d.c. permanent-magnet motor is supplied from a 50V source through a fixed frequency series p.w.m chopper. At normal motor ratings the armature current is 30A and the speed 1000rpm. The armature resistance is 0.2Ω and the device voltage drop can be considered to be 0.5V. Assuming the motor’s electrical time constant is considerable greater the the switching period:

Calculate…  Duty cycle at a specific operating point.  Thermal design of the heat sink.

Concluding Comments  Don’t forget electrical power engineering.  Realistic design questions will cover a wide power range.  DSP are as valid in communication systems as in variable speed drives.  Question bank is also a knowledge repository.