Tech Notes

Issue 4 and Volume 16.

Regulator developed for single-phase generators

A final-year engineering student at Monash University in Australia has designed and built a regulator for a self-exciting single-phase induction generator for a micro-hydro system. In essence, the regulator maintains constant output alternating current (AC) voltage and frequency as system conditions (such as water speed or electrical loading) change, says developer Luke Robinson.

By providing an alternative method to regulate the AC output of an induction machine, project owners can avoid the cost of battery banks, Robinson says. The regulator provides power up to 500 watts but can be scaled to suit a particular induction machine.

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Single-phase machines often are more suitable to the power requirements of remote communities. They are less expensive than three-phase generators and are more robust than their direct current (DC) counterparts, Robinson says.

He has tested the regulator using a DC drive in the laboratory. However, it has not yet been tested at a hydroelectric project.

— For more information, contact Luke Robinson, Sinclair Knight Merz, 590 Orrong Road, Armadale, Victoria 3143 Australia; (61) 3-95086208; E-mail: [email protected]; or Grahame Holmes, associate professor, Monash University, Wellington Road, Clayton, Victoria 3168 Australia; (61) 3-99053474; E-mail: grahame. [email protected]

ICOLD Forum: Embankment dams on permafrost

In the world’s far northern areas, the combination of deep rivers, favorable engineering and geological conditions, and low agricultural value of flooded areas offers multiple sites for large water impoundment structures. However, construction of hydraulic structures in areas where permafrost is found — called cryolitic zones — faces specific challenges. Cryolitic zones occupy more than 25 percent of the total land area on earth and 65 percent of the territory of Russia.

Because of natural conditions in these areas and the lack of developed transportation infrastructure, dams typically are built using local materials. This involves embankment dams — typically earth and rockfill with a central core.

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The International Commission on Large Dams (ICOLD) offers a technical bulletin on building embankment dams on permafrost. Bulletin 133, Embankment Dams on Permafrost, was prepared by the ICOLD Committee on Materials for Fill Dams. This committee is made up of 24 members from 23 countries.

The bulletin identifies conditions that determine the construction and operation of hydraulic structures in cryolitic zones, such as climate, engineering-geological conditions, and hydrological regimes. It discusses the main design and layout trends of dams built in these regions, foundation treatment, and passing of diversion flows and ice. The bulletin also covers specific operation, repair, and rehabilitation of embankment dams in the region, with case studies.

The 165-page bulletin is intended for geological engineers, designers, and builders of hydraulic engineering structures. To order this bulletin for 35 euros (US$55), visit www.icold-cigb.org and click on Publications, then Bulletins.

— ICOLD is a nongovernmental organization that provides a forum for the exchange of knowledge and experience in dam engineering. The organization leads the profession in ensuring that dams are built safely, efficiently, and economically, and without detrimental effects on the environment. To learn more about ICOLD activities, contact Michel De Vivo, Secretary-General, ICOLD 151, Bd Haussman, Paris 75008 France; (33) 1-40426824; E-mail: secretaire. [email protected]

This regulator, for a self-exciting single-phase induction generator for a micro-hydro system, was developed to maintain constant output alternating current voltage and frequency as system conditions change.