After the generator is spun, depending on the stator residual magnetism, after the trio-time harmonic
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secondary winding senses the residual magnetism voltage, circuit is rectified through the single-phase
rectifying circuit bridge into direct current (DC) to provide excitation current to the exciting winding through
brush slip ring, which finally establishes the main rotor magnetic field. When the generator’s rotary speed
reaches at a certain value, no-load voltage is established.
When trio-time harmonic wave excitation generator is running on load, it has self-excited function to keep
generator terminal voltage at a constant value. Furthermore, generator with automatic voltage controller/
regulator which adjusts the excitation current will lead to more accurate generator voltage output. At the same
time, the automatic voltage controller/regulator can also replace the regulating resistance to stabilize the
voltage.
Installation Requirements
There should be no space between turbine base and turbine pier. Any water splashing or water leakage is
definitely not allowed in their connection surface.
Installation Procedure
1. Based on the rated head and water flow required by the unit, choose a good and ideal installation location.
Inspect the whole turbine generator unit before installation, and check whether the size of tailrace (water outlet)
and reserved holes for unit footing fulfill the designed requirements. If not, it should be amended before
installation.
2. Then, use concrete to pour turbine pier. When making the pier, the water outlet should be 3 times larger than
the water inlet. Reserve places on the pier for anchor bolts according to the size and situation of anchor holes
on the turbine. After these, put the anchor bolts into the reserved holes for unit footing, then pour with concrete.
After the pier is completely solid, maybe a week later, place the unit and tighten the anchor nuts (follow the
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order of diagonal line) and fix the unit with wood or steel cross arms. Then pour concrete again to connect
closely the unit and turbine pier. Any gap between them must be sealed with concrete, and water leakage is
definitely not allowed. A leveling instrument should be used to measure levelness when install the unit to make
sure it’s fixed in a horizontal position. After the unit has been installed, check again and rotate the runner shaft
of the turbine by hand. If it rotates flexibly, the installation is completed.
Pipe Installation
Water from pressure forebay flows through the pipe into the turbine. The pipes are installed after the
downstream of forebay and upstream of turbine valve as a connector between them.
Steel pipes welded with flange are commonly used in micro hydro power unit. The flange pads should be
placed in the up-straight position, in order not to reduce water cross-section. Nuts of the pipe joints should be
tightened gradually in a diagonal order.
Basic Requirements on Pipe Installation
Buy pipes according to the required diameter by the unit. Smaller diameter than the required diameters is
definitely not allowed! They should be straight and avoid any crooked part. The angle between pipe and
horizontal level of ground should not be less than 25°. If not, the pipes will be longer and the water head will be
decreased, which will lead to inadequate power output. It is better to use a horn-type mouth pipe as the water
inlet pipe which is installed in the wall of reservoir or forebay. The distance from the lower edge of horn-type
mouth to the bottom level of reservoir or forebay should be larger than 0.2 meters. The Inner diameter of
expansion joints should be the same as pipe diameter. But too many joints will cause loss in water head.
Anchored pier: Pressure is the highest in the joints of water inlet pipe and turbine nozzle, so anchored piers
made by stones or concrete are needed to be built to fix the metal pipe.
Supporting pier: Due to the weight of steel pipe itself and water, and pipes are long, they are easy to bend or
become deformed, so supporting piers must be added in their middle parts. The best installation place is the
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joints between steel pipes.
Inspection after Pipe Installation
1. Whether there’s water leakage in the pipes or joints. If any, find out the reason and process it immediately.
2. Litters left while installation should be cleaned up to make sure water is unblocked.
3. Whether the pipes will become bended or deformed and whether they are firm enough after they bear the
water pressure. If any problems, it should be dealt with in time.