Introduction:
It is a known fact that lots of micro-hydro systems are in operation in our country, Nepal. They have been playing a great role to provide electricity to local communities. But one problem is typically seen in most of the micro-hydro systems. There is fluctuation in frequency generated by the generator which causes adverse affect in various electrical appliances. A controller is required to solve this problem. We have come up with “Design and Manufacture of Electronics Load Controller” which is meant to construct an ELC (Electronic Load Controller) that controls the frequency of the generated voltage in the micro-hydro systems.

Objectives:
The main objectives of this project are:
Ø To design and construct an ELC.
Ø To minimize the problems in existing ELC.
Ø To interface the constructed ELC to the computer.
Ø To construct a PC based data logger that logs the performance of the ELC.

Background
In Nepal, almost all of the micro hydro systems are based on run-off-river type. Storage system has not been put into practice because of its high cost. This result in the generation of constant power by the generator but the consumer load may vary from time to time. In the case of peak load almost all the generated power is consumed but when the required load is less than the generated power the voltage and the speed of the generator increases which causes serious problems in the appliances used by the consumer and other system components such as transformer and motor loads. Over voltage may cause overheating, reduction in life of different devices whereas under voltage reduces the heat output in case of heating devices and intensity of lighting devices. Fluorescent lamps will not even light if the voltage is down by 15%.
To overcome such problems, Electronic Load Controller (ELC) is used such that the generator faces a constant load all the time. Due to cost factor synchronous generator with AVR are not used. Induction motor that can be used as generator is used in most of the micro hydro schemes because of their low cost. But there is no provision for the AVR in induction generator. The induction generator version of ELC is known as Induction Generator Controller (IGC).
After the ELC is installed in the micro hydro system, its performance needs to be governed continuously. In many of the cases the operator may not even know if the ELC is in working condition or not. To overcome that and make sure that the ELC is functioning well, we have designed a interfacing system to show the output of the generator in terms of voltage and frequency. For that we have designed a system that interfaces the ELC with the computer. A sample of voltage generated by the generator is fed to the computer via the interfacing circuit and is displayed continuously in the computer. On top of it, the results are logged in frequent intervals of time to check the performance the ELC in later times.
The conventional governors made using mechanical and hydraulic governors to control the flow of the water in the penstock are uneconomical. Thus, in micro hydro systems in which cost is the major factor electronic governor the ELC is the best way of controlling the speed of the generator.
The electronic load controller is an electronic device that maintains a constant electrical load on the generator in spite of changing user loads. This permits the use of turbine with no flow regulating and their governor control system.
The ELC maintains a constant generator output by supplying a secondary ballast load with the power not required by the main load. Consider the plant running at near full load and governed by an ELC. If the consumer switches off some appliances then less electrical power is used while the same water power is maintained to the plant causing increase in speed and frequency of the turbine and the generator. The change is speed and frequency is sensed by the ELC. The ELC then adds a ballast load of sufficient resistance at the generator output to dissipate power equivalent to that which was switched off. Thus in spite of change in consumer load the total load on the generator remains constant.