Load Controllers, 555 Timers and Generators

Work here in Sabah has begun, As I mentioned in my first post, I've been asked to focus on the controller for a micro-hydro system. What I didn't clarify in the post is that there are typically two types of controller used in micro-hydro systems and the controller chosen depends on the electrical generator installed. 

Electronic Load Controllers (ELCs) which I spoke about in the first blog post, are used with Synchronous Generators. The main principle of the synchronous generator is that the rotational speed of the rotor in the generator is directly proportional to the frequency of electrical signal produced by the generator.

Induction Load Controllers (IGCs) are used with Induction Generators. But I'll go into more detail about these types of controller and generator in a later post.

For most of  Tonibung's micro-hydro projects they have purchased both controllers as off-the-shelf products from Renerconsys - a micro-hydro manufacturer in Indonesia. Now they are keen to progress towards developing their own ELCs and IGCs. So for my first day at work I wanted to get an idea where Tonibung were in this development process. I was presented with an ELC design a past volunteer (not EWB) had developed for a micro-hydro project. I was told that Tonibung and the volunteer had pursued the design, built it and tested it with a micro-hydro system. It turned out that the controller design didn't not work and they wanted me to look into the problem. The design can be seen below.

ELC design with 555 IC Timers

The ELC design Tonibung had used was quite interesting and wasn't what I had expected. The design converts the AC output signal from the generator to DC and then uses two 555 IC timers. The first timer is used to detect changes in generator output voltage and then the second creates a Pulse Width Modulation (PWM) signal to a ballast load based on information from the first timer. Theoretically, when the user consumption load changes, the voltage on the generator will change and the controller will adjust the split between user load and ballast load. The main thing to strike me about this design is that it is regulating the load by detecting changes in voltage. This is different from typical ELCs that regulate through changes in generator output frequency.

ELCs are used with Synchronous Generators. Synchronous Generators are equipped with an Automatic Voltage Regulator (AVR). The AVR provides a constant voltage output from the generator despite change in load. See where I'm going with this? When testing this ELC the Synchronous Generator was equipped with an AVR, meaning the voltage will not change. The ELC wouldn't function because there is no change in voltage from the generator. Hypothetically this ELC could work if it were to bypass the AVR and be connected directly to the generator. But there is little point in doing this because the AVR available. An ELC needs to be developed that controls the by detecting changes in frequency.

 Renerconsys supplied Electronic Load Controller

Here at the Center for Renewable Energy and Appropriate Technology (CREATE) the village trainees are spending two years learning and building skills on how micro-hydro systems are developed, operated and maintained. Once completed they will return to their village and become the micro-hydro technician. Throughout the two years, the trainees will complete several training modules that are essential for understanding micro-hydro. These modules are:

• Surveying and Feasibility
• Civil Engineering
• Mechanical Engineering
• Electrical Engineering
• Operating and Maintaining

I  have been asked to develop the Electrical Engineering Training Module. This module will provide information on the electrical aspects of the micro-hydro system, from the electrical generator right through to the domestic wiring of circuit breakers and light sockets.

Earlier this week I observed the trainees attending an electrical wiring tutorial session. This was located in the CREATE classroom. The trainees were asked to wire together circuit breakers, light sockets and plug sockets. It was interesting to watch and beneficial to get a reminder on the wiring, Unfortunately with the language barrier I couldn't really get involved as much as I would have liked.

Electrical Training in the CREATE classroom

Village trainees practising wiring circuit breakers, lights and plug sockets