However, there is still a chance that the fluctuation in speed will affect the frequency and voltage output of a generator negatively. In fact, it could harm and damage the generator by overloading it with high power or over speeding it with a light or no load at all.
To prevent damage, electric load controllers or ELCs are used. For smaller micro hydropower systems that use an induction generator, induction generator controllers are used.
An induction generator controller is a device that regulates the power of an induction generator that turns a turbine. It helps keep a constant load of power to a turbine of a micro hydropower system. Because of the constant load, the turbine can generate stable voltage and electricity.
To understand how an induction generator controller works, lets look at how an ELC regulates power. An ELC, which is used by synchronous generators instead of induction generators, counteracts the main load. Counteracting involves varying the amount of power that is dispersed in a resistive load, called a ballast or dump load. Usually, the ballast or dump load are in the form of water heaters.
The distribution keeps the electrical load of the turbine and the generator constant. The electric load, or frequency, is directly proportional to the speed of the turbine.
An induction generator controller basically works like an ELC, only that it is used in an induction generator.
Also, an induction generator controller can be used as a load management system. It does this by assigning a secondary load. Thus, excess power is diverted to other utilities such as water heating or space heating system, rather than sending it to the ballast load. Due to this function, it is possible to hook up other loads by a sequence of priority.
Induction generator controllers that are available in the market can be used for micro hydropower systems that generate between 1 kilowatt to a hundred kilowatts of power. They are contained in weatherproof enclosures that can contain power meters, safety devices, switchgears and connection outlets.
One last note about controllers, when activated, can cause some radio frequency interference. So, it is important to keep radios and walkie talkies away from them.