There are two types of generators used in micro hydropower system. These are synchronous and asynchronous generators. Synchronous generators are standard in most power generators. On the other hand, asynchronous, or induction generators, are also used. For this article, we will tackle the second type in detail
An asynchronous or induction generator is available in three phase or single phase systems. The hydroelectric systems capacity, its type of load and the systems transmission and distribution of electrical power are the determining factors of what system should be used.
It is easy to understand how it works. A conductor is placed and exposed in a moving magnetic field. When the conductor moves, it generates voltage.
For small hydropower systems, an induction generator is preferred. Thats because they are rugged, more compact and cheaper than synchronous generators. Most of these types of generators have a three phase induction motor installed in them. The capacitors that are used to charge an induction generator for small hydropower systems generate less than 10 to 15 kilowatts.
Induction generators should be operated and maintained at a constant. The number of poles determines the speed; the more poles, the lesser the speed. 4-pole generators that have a rotational speed of 1,800 rounds per minute are ideal on small hydropower systems. 2 pole generators produce 3,600 rounds per minute which is too powerful for such a strong system. For induction generators that operate at less than 1,200 rounds per minute, are quite expensive and for it to match the speed of the turbine, a gearbox or a belt might be needed.
The electrical power that is generated from an induction generator can either be alternating current or direct current. Direct current has the advantage of storing electric power into batteries easily. Alternating current allows the user to power up common household appliance and powered tools. Alternating current also is much more economical and efficient with regards to the transmission of electrical power.
Induction generators that produce alternating current are also referred to as alternators. The alternators vary the voltages, from above to below zero voltage. It is this process that produces alternating current. This is the same process that is used in large hydroelectric power plants, nuclear power plants and even your car. Only the speed varies.