Induction Generator. Many small turbines use variable frequency alternators. Because the voltage and frequency of the electricity generated by these turbines varies with wind speed, the electricity they produce is incompatible with the utility grid. The power must be conditioned with an inverter before it can be interfaced with utility power. Inverters are complex, expensive and, oftentimes the most vunerable trouble prone component of a wind turbine installation.
Induction generators are very similar to the induction motors which are used almost exclusively on every piece of rotating electrical machinery being produced today. They are simple, robust, reliable, efficient and trouble free. Because induction generators contain no solid state components, they are not subject to voltage transient such as lightning, which can easily damage the sensitive electronic components of an inverter.
BECAUSE INDUCTION GENERATORS MUST HAVE UTILITY POWER AVAILABLE BEFORE THEY CAN PRODUCE POWER, THEY ARE INHERENTLY SAFE AND CANNOT ENERGIZE THE GRID WHEN UTILITY POWER FAILS
Induction generators are also inherently safe. In order to produce power, induction generators take their excitation (reactive power) from the utility grid. If grid power becomes unavailable, the generator will not product power. This eliminates the possibility that the turbine can backfeed power into the grid during a power outage and potentially injure someone working on the lines.