We have recently turned our attention to the electrical installation market here in the UK. In the UK this means the popular City and Guilds 7202 and 2365 courses at level 1 and 2 respectively.
Included in the list of concepts that we want to explain to students are the technical differences between the Earth and Neutral wires in the UK mains electricity system, and how safety systems operate. Also we want to give students experience of Circuit Breakers and Residual Current Devices to provide safety cut outs for consumers.
The problem here from a teacher’s perspective is safety: although there are learning systems in Europe that allow students to perform experiments with mains level voltages, it kind of goes against the grain to let students loose on them. Also the safety systems you need to put in place to allow safe operation by students are really expensive, and really limiting. So we sat down with our authors, teachers and our engineers and brainstormed what we might do.
The results are really exciting: our engineers have developed an educational Residual Current Device. You can see that in the photograph below.
This is the first prototype. The final design will fit underneath a standard Locktronics carrier which will be printed with a circuit symbol representing the circuit breaker.
The board is a four terminal device – two input wires representing ‘Live’ and ‘Neutral’ in and two output wires representing ‘Live’ and ‘Neutral’ out. The circuit board contains a small four winding transformer and amplifier. When there is a difference between the current passing between the ‘Live’ and the ‘Neutral’ pathways the difference is amplified and fed to an on board microcontroller. The microcontroller controls two relays which isolate the input from the output. So this is pretty much the same as a standard RCD. However our version works at just 12V AC so it is perfectly safe for use in the lab as a learning tool.
The device itself works really well: simply touching the ‘Live’ or the ‘Neutral’ contacts after the RCD triggers the relays and turns the supply off. But the system is happy passing more than 1 amp at 12 V AC to a load.
Now we have this technology we are starting to think about the exercises students need to go through to learn about RCD behaviour and Earthing systems. If anyone out there has any opinions we would love to hear from you.
Electrical Installation kits for training electrical wiring courses will be available from Matrix TSL from January. Give us a call on 01422 252380 if you would like a demonstration or to speak in further detail.