The 'Humming Bird' Electronic Load Controller / Induction Generator Controller

by Jan Portegijs

An Electronic Load Controller (ELC) keeps a synchronous generator driven by a Micro Hydro turbine running at constant frequency irrespective of electrical loads. An Induction Generator Controller (IGC) does about the same for an asynchronous motor + capacitors that is used as generator. An ELC or IGC might be the hardest part to get or build because it involves electronics and proven designs are hard to find. Well, here is mine:

On this site:

  • The building manual can be downloaded as a zip-file by clicking on the following link: (ca. 0.9 MB, December 2000 version).
    After downloading: Unpack the zip-file and open `humbird.doc' using Word 97, see `readme.txt' for more details. If you already have the June 2000 version: Differences are slight, no need to download this new version
  • More about the design.
  • Experiences from people who built it.
    Mr. Kumar Fonseka has built and installed many ELC's / IGC's, so a special page on his experiences.
  • 3-phase version, for larger capacity M.H. systems where 3-phase generators are more economic. Click on to download the building manual (ca. 0.6 MB, December 2000 version).
  • Related site: The Firefly' building manual is now available in *.html format. The firefly system consists of a charger station (a car alternator with small crossflow runner fitted straight to the shaft) and for each house: A home system (a 12 V car battery or special `solar' battery, lamps, wiring, switches and a charge indicator).
    There are also pages on experiences with the firefly, short article, technical issues
  • Something completely different: `Swingcat' Tidal Turbine for generating power from tidal currents.

New (dec. 2006) Network site:

  • I started a new 'humming bird' network site, hosted at my own provider so that I can update it easily. Any new information will be added there. I do not have much to add myself, what I can do, is to facilitate contacts between people interested in the humming bird design. Currently, there are pages on:
    • Market place: Controllers, parts, services etc. offered for sale, or wanted to purchase.
    • Experiences: Stories of people who used the humming bird.
    • Overview: Use of humming bird design worldwide.
    • Various, questions and answers, whatever comes up...
    As of now, these pages are still quite empty, I hope that this will change in the near future. So if you have (tried to) build or buy a controller: Have a look at that site, see whether your story fits in there and if so: Fill in the questionnaire and send it to me.
    If you know someone else who built a humming bird controller: Please forward the site to him/her or send me the email address so that I can contact him/her.


About the Humming Bird ELC/IGC

An Electronic Load Controller (ELC) is used in Micro Hydro schemes with a synchronous generator working as a stand-alone generator. Together with the dump load(s) connected to it, it works as an electrical brake to the generator: It diverts so much power to the dump load(s) that frequency is kept at nominal value. This way, there is no need for turbine with a governor to control generator speed. Governors used to be the most expensive and least reliable component in M.H. schemes in the past. 

A recent development in Micro Hydro technology is the use of an induction motor (the standard industrial motor) with a suitable set of capacitors as generator, and an Induction Generator Controller (IGC) to keep voltage in check. Due to characteristics of the induction motor with capacitors, also frequency is kept reasonably constant as long as power factor of user loads is above 0.8. In Nepal and Sri Lanka, many of such schemes have been installed and results are positive (see Harvey, Adam e.a. 1993: Micro Hydro design manual, a guide for small-scale water power schemes, IT publications, London).

Harvey recommends induction generators for systems below 30 kW capacity as induction generators are cheap, robust, can stand overspeed, require very little maintenance and are available with lower nominal speeds so that transmission ratio can be lower. Only above 30 kW, a synchronous generator would become cheaper than an induction generator with capacitors.

However, also below 30 kW, a synchronous generator with ELC might be advantageous because: 

  • It allows loads with a poor power factor (provided that the generator is sized accordingly). 
  • It allows heavier electrical motors to be started direct on line. 
  • Modern generators are available as spare parts of generator sets. These also require little maintenance and are widely available. Those types that have a nominal speed of 1500 or 1800 RPM (the ones that are normally driven by a diesel engine) probably can stand 70 % overspeed and are suitable for a M.H. scheme with a crossflow turbine. 

Initially, the Humming bird was designed as an ELC. The present design can be modified into an IGC by adding some extra electronics.

Existing ELC/IGC designs can be classified in 3 types: 

  1. With `phase angle' regulation and one, large dump load (or 3 for 3-phase versions). With these, the power component of the ELC is a triac or thyristor, just like in an ordinary light dimmer: The dump load is switched on at a moment (expressed as a phase angle) in each half period of voltage signal. The triac switches off by itself when current through it drops to 0 by the end of each half period.
  2. When a large dump load is switched on while voltage is at its highest (so with phase angle is ca. 90°), generator current is seriously distorted. This makes that generator has to be oversized by some 25 % when such an ELC is used.
  3. With a `binary' set of dump loads. `Binary' means that each next dump load has twice the capacity of the previous one. Here, each dump load is switched either completely on or completely off, so no distortion of generator current. By switching on different combinations, power diverted to dump loads can be regulated in small steps. 
  4. Such a system will be quite expensive because of the costs of solid state relais and the set of dump loads with the right capacities.
  5. With `pulse width regulation (also called `mark-space' regulation). Here, the AC voltage is first rectified and dump load is switched on and off with a variable duty cycle. The well-known IGC's developed by mr. Nigel Smith work this way.
  6. For this, modern IGBT transistors are used that can switch off current at any moment. Total heat production is higher because dump load current passes both the rectifier and the transistor 

The humming bird ELC has a bit of the first two types. It uses phase angle regulation, but with 2 (or 3) small dump loads instead of one large one. Phase angles for these dump loads are regulated such that if one dump load has a phase angle of 90° (the worst case), the other one is either completely on or completely off. This makes that distortion of generator current is much less than with one large dump load and there is no need to choose a 25 % oversized generator (see type 1 above). Normally, a 5 % oversized generator will do for the 2 dump load version and for the 3 dump load version, the effect of distorted generator current is no longer decisive because the power factor of user load will require a larger generator already.

Some other features of the humming bird ELC are:

  • It uses only simple, cheap and widely available electronic components.
  • The electronic circuit is insensitive for noise signals. Even without capacitive or resistive load connected to the generator (the worst case with respect to noise), it works fine.
  • User loads are protected against overspeed, overvoltage, undervoltage and, optionally, underspeed. The ELC itself is protected against overheating. Only an overcurrent protection as recommended by the generator manufacturer should be added.
  • The present design is a 1 phase ELC with a capacity of 7 kW (2 dump load version) or 10 kW (3 dump load version). Capacity can be increased by making a 3 phase version (with a capacity of 21 kW for 6 dump loads or 30 kW for 9 dump loads) and by using thyristors as power elements instead of triacs. With thyristors, capacity can be made as high as one might desire. These are also cheap, but require a slightly more complex triggering circuit.
  • For reliable operation, the ELC is fitted in a compact, watertight `class IP55' housing with the heat sink at the outside. It weights only ca. 1.5 kg.
  • It is cheap: For a series of 20 pieces built by a professional electronics workshop in Holland, production costs would be ca. US$ 300 per piece. With Dutch retail prices, components for one piece are ca. US$ 125. In third world countries with some electronics industry, prices might be considerably lower.

I think that for succesful M.H. introduction, components should be produced within country as much as possible. This way, the extra costs in terms of money and time for importing components are saved, getting broken components repaired is easier and the scheme as a whole becomes more inspiring because it uses no imported technology. So if organisations or workshops want to set up production of this humming bird design, I would like to help them.

For organisations or workshops that need one or a few ELC's for trying them out in a pilot scheme, it is worthwhile to postpone the investments in starting local production until after the pilot phase and data on how much ELC's are needed, are available. Then maybe one of the people who has built an ELC already, could build extra ones for you at a decent price.


Humming Bird ELC/IGC: experiences until now

De La Salle University, Philippines

They bought an ELC of an earlier version from me and installed it 1996. Apparently it broke down 4 times and each time, it was succesfully repaired. Unfortunately, they did not report any details. They had electronics students doing graduate projects on improvements so I guess they wanted to develop their own design. In Hydronet 2-3/96, there was an article: ORETA, Andres and SALAZAR, Godofredo, 1996: Micro hydropower initiatives in Abra, Philippines.

The following people have built ELC's / IGC or seriously intend to do so. They all used previous versions of this manual that describe the same design as the present, final version.

Mr. Muhammad Ali Siddiqui and Mr. Muhammad Asim Zaman Khan, Pakistan

Mr. Siddiqui (sorry, no up to date email address available) is student at Mechanical engineering at Ghulam Ishaq Khan Institute of Engineering Sciences and Technology. As his final year project, he designed an M.H. system in cooperation with the Pakistan Council of Appropriate Technology. He contacted me in June '99. Mr. Khan is a student Biomedical Engineering at Sir Syed University of Engineering. He did most of the building work on the ELC, using a PCB provided by me. They could not get all components and most of their questions were about using alternative components.

Their first ELC (see picture) was tested using mains voltage in January 2000. By then, apparently Mr. Siddiqui's final year project ended and they could only work on it during holidays. The ELC was tested with a generator set and was scheduled to be installed third week of May 2000. Mr. Khan started building a second ELC for himself. Mr Siddiqui graduated as the best of his year. He planned to go to the USA for an MSc course in Design and Manufacturing.

Mr. Kumar Fonseka, Sri Lanka / Canada

Mr. Fonseka first contacted me in November '99 and by February 2001, he got his 6-th Micro Hydro project running. All these M.H. projects were equipped with single-phase IGC's. To increase capacity, he used pairs of anti-parallel thyristors (instead of triacs) and got these running without major difficulties. For another project, he built a 3-dump load IGC with high-capacity BTA triacs. End of 2001, mr. Fonseka moved to Canada but he continues to work on M.H. projects in Sri Lanka

For more info, see mr. Fonseka's experiences.

mail to

Mr. Fonseka also built ELC's / IGC's for sale. A 3-phase ELC was bought by:
Mr. Jose Antonio Castro, Spain
, see mr. Castro's experiences.

Mr. Richard Harker, USA

Mr. Harker (sorry, no up to date email address available) wants to power his house using a crossflow turbine with an 1.5 kW induction generator installed at a drop in an irrigation canal. His IGC is nearly finished and when it performs well in his tests, he might want to build units for sale to other people. Mr. Harker is an electronics engineering technician and asked only some details about component specifications.

Mr. Horacio Drago, Argentina

Mr. Drago (sorry, no up to date email address available) builds pico hydro units for battery charging, with a Turgo turbine coupled to an asynchronous generator with the output voltage being rectified. He has ordered 3 Printed Circuit Boards with me. He wanted to start building in the middle of 2000 but that has been postponed. Initially, he was interested in the IGC version. As far as I know, he now wants to build standard ELC's first.

More experiences??

If you have used the humming bird design and would like to share your experiences: Send me a report, pictures or the URL of your homepage and I will include it in this page.


Swingcat Tidal Turbine

I also worked on the 'Swingcat Tidal Turbine' concept. It is not `micro' in its scale and technically quite complex. I think it will keep me busy for the next couple of years: Until either I find out why this wasn't a good idea after all, or I can prove it is an economically feasible form of renewable energy and things get started for real. Click on (ca. 0.6 MB) to download a report on it.

The Swingcat vessel (click on it for a full scale view): It sails to and fro like a sheer-ferry on a long anchor cable, driven by the tidal current that generates lift forces on its keels.



  Jan Portegijs
  Gelaarsde Kat 115,
  5629 KJ Eindhoven, Netherlands

  Note: To avoid spam, email addresses are hidden by a script.
  If you don't see an email link below, enable "javascript" in your browser.
  mail to


More information on hydropower at the microhydro webportal

Last modified on 16 December 2006  since 3 June 1999
FastCounter by bCentral