New Zealand Certificate in Electrical Engineering Theory (Level 3) Stream B (2020)

A practical guide to using your calculator. This is not aimed at any particular model of calculator.

Your calculator may have special features or particular ways of performing operations. Consult your calculator's manual.

These are the slides delivered on Monday 15 June and Tuesday 16 June 2020, on series and parallel circuits.

For the circuits in the last two slides, please view the Answers and Commentary to get see the solutions.

Introduction to units of measurement, including the seven SI base units and some electrical units.

Kirchhoff's law and basic resistance circuits.

Updated on 6 April 2020 with page numbers.

The answers to the worksheets are on pages 50 and 51.

The introductory mathematics workbook.

This book covers conductors and insulators.

Some slides on conductors and insulators.

Resistors and Resistance - Slides

This is quite a good online resource about the basics of resistors.

This video is a good demonstration of a three-heat switch setup. It is similar to the three heat setup you will be asked to construct in the practical classes. There are also assignment questions on it.

Please note that some aspects, such as terminal connections may vary, but the principle is the same.

Scalars and Vectors

This presentation was delivered on 17 June 2020. I will fully cover slides 42 onwards in subsequent lessons.

The most relevant slides for the Summative Test 1 are slides 31 through 33, about the crane lifting a mass.

See also Question 23 in the Summative Test 1 practise test.

This video is a demonstration of overloading a 1 mm² twin and earth cable with various currents beyond its rating.

The author is based in the UK, but the cable is otherwise similar to cables used in New Zealand.

The Nexans/Olex Cables 2019 cable catalogue.

This catalogue may also be downloaded from Nexans's own website.

NOTE: This catalogue is being used as an example of a cable catalogue, and not as a commercial endorsement of Nexans and Olex. The behaviour of other brands of cables should be similar.

This catalogue has a range of information from AS/NZS 3008 about cable selection, voltage drop, and short circuit current withstand.

At low currents (<100 A), the cable rating is generally defined by the protective device rating.

At higher currents, the protective device can be programmed to accommodate the cable capacity.

In general, for most low current jobs the "rule of thumb" section C3 in the Wiring Rules may be used.

I would advise that for any household wiring, that the "bulk thermal insulation, partially surrounded" rating is used. This covers wiring in contact with the surface of thermal insulation, as well as cables between thermal insulation, and a non thermally insulating surface (e.g. cables clipped to wood and in contact with thermal insulation).

For TPS, the most relevant pages are pages 44-45. The ratings for "surface clipped" (the right set of columns) mostly corresponds to "in air" ratings in section C3. Note that the rating may vary depending on the interpretation of AS/NZS 3008, and the exact construction details of the cable of interest.

Sections C3 provide "simplified" selections of protective device ratings for a given cable size in a given range of situations, and calculation of voltage drop.

As discussed above, all cables installed in domestic housing should be treated as "bulk thermal insulation - partially surrounded".

The ratings here are more conservative than those in AS/NZS3008, in the sense that the protective device rating is the limiting factor on cable current capacity rather than the cable itself.

The voltage drop may be slightly over estimated. This is not a problem if the simplified calculation is below any target voltage drop. Bear in mind that in many cases a calculated result that is slightly over the allowed design value is ok if the full conditions of diversity and maximum demand are taken into account.

ECP 50 gives information about the repair and maintenance of domestic appliances by the appliances owner. However, it still contains plenty of useful information for electricians.

ECP 51 gives information about the repair and maintenance of domestic wiring installations by the home owner. However, it still contains plenty of useful information for electricians.