1. Transformers & Electrical Distribution Systems HSC Module 9.3 Motors & Generators Copyright Jeff Piggott, 2003. All rights reserved.

6. Step-Up Transformer Flux.  AC Input Primary Coil Secondary Coil Core AC Input Flux.  AC Output ( increased! ) Primary Coil Secondary Coil Core # turns on secondary > # of turn on primary n s > n p

9. Step-Down Transformer Flux.  AC Output decreased Primary Coil Secondary Coil Core AC Input # turns on secondary < # of turn on primary n s < n p

16. Core Laminations Splitting the core into laminations – thin sheets – reduces effects of eddy currents by restricting them to shorter pathways. Laminated iron core Insulating layers

17. Effect of Core Lamination Thickness 0.50 0.0127 0.75 0.0254 0.85 0.0508 0.90 0.10 to 0.25 0.95 0.27 to 0.36 Eddy Current Losses Lamination Thickness (mm)

18. Transformers & Electrical Distribution In Australia, 23,000V AC generated, 330,000V or 500 kV AC HV transmission line, 240VAC 50 Hz end use single phase, 415VAC 50 Hz 2 and 3-phase.

23. Electrical Transmission Lines – Insulation of Wires In dry air, electrical sparks can jump the following distances for the given potential differences: 10 000 V --------- 1 cm 20 000 V --------- 2 cm 100 000 V ------- 10 cm 330 kV -------- 33 cm *Distances smaller in very humid air

33. Transformers & Electrical Appliances in the Home Electronically operated domestic appliances require both a step-down transformer to change 240 volts to about 5 - 20 volts & a rectifier to change the low voltage AC to DC. TV, stereo, computer, CD player, clock radio, fluorescent lights, home security systems, microwave oven, answering machines, air conditioner, fax machines, washing machines, microwave oven kettle, hot water heater, toaster, older room heaters, hair dryers, incandescent lights, old model refrigerators, some clothes dryers Appliances with a transformer Appliances without a transformer

35. Energy Transfers in the Home (2) Copy and complete the table below.  Washing machine  VCR  Hair dryer  Electric drill  Air conditioner  Blender  Radio  Television Energy Transformation Household Appliance

41. Effect of High Voltage Power Lines on Humans Alternating E field induces an alternating current to flow in body Sign changes 100 times/ s. + - - - - - - - - - + + + + + + - - + + + + + + + + - - - - - -- +

43. Phasing and em Radiation Exposure Levels Phasing assists to reduce the E fields when multiple power lines are present. “ Code” related health effects refer to wiring codes where the conductors are far apart. The closer the supply and return wires are together, the lower the fields due to phase cancellation - - - - - - - - - + + + + - + + + + + + + + - +