Design, Construction and Testing of Generator for

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Hydro-electric generator is the energy-converter of the mechanical energy ... Design of electrical machines mainly consists of obtaining the dimensions of the ...

Paper - 444

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U Aung Ze Ya1

Abstract Community-owned hydropower plant is the most suitable power source for communities living in the rural and hilly regions. Therefore, community-technology of hydropower is also needed to fulfill the requirements in non-electrified areas. The theme of this paper is the design and construction of a Hydro Power Plant with emphasis on the generator. And it is also intended for rural electrification. In this study, two generators are designed. Three-phase, 62.5 kVA, salient pole, synchronous generator is designed for 50 kW hydropower plant. And single-phase, 2kVA, salient pole, synchronous generator is designed for 1.6 kW hydropower plant. Construction of 2kVA salient pole, synchronous generator and the performance testing of 1.6 kW hydropower project are also done in this study and presented. 1.6 kW hydropower project can distribute the community-technology of hydropower.

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Introduction

Hydro-electric generator is the energy-converter of the mechanical energy into an electrical energy. There are two main types of an ac generator which are used in hydro-electric scheme. They are: (i) Synchronous generator and (ii) Induction generator

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Selection of Generator

Criteria for selection of generators are: (i) Maximum turbine power (ii) Run away speed of turbine (iii) Horizontal or vertical construction (iv) Whether isolated or parallel operation (v) Constant load or variable load (vi) Availability of grid supply (vii) Reactive power supply

1

Lecturer, Electrical Power Engineering Department Yangon Technological Univesity, Yangon, 11011, Myanmar.

Design, Construction and Testing of Generator for Hydropower Plant

Design, Construction and Testing of Generator for Hydropower Plant

Design, Construction and Testing of Generator for Hydropower Plant

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The following table can give the guidance on the selection of type of the generator.

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From the above table, synchronous generator has many advantages over an induction generator. Therefore, the synchronous generator is selected for hydropower plant.

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Salient Pole Alternator

It consists of two major parts: (i) Stator and (ii) Rotor

(i)

Stator

Stator Core is built up of laminations, using 0.5 (or) 0.4 mm thick, dynamo sheet steel, with low specific loss. Laminations are insulated from each other by providing a special vanish on both sides of laminations. Slots are provided to accommodate the stator winding as shown in Figure 3.

Normally the stator laminations are punched in the form of segments. The outer diameter of stator frame is quite large for these generators.

(ii)

Rotor

Rotor of water wheel generator consists of salient poles. Pole is built up of thin steel plates, which are clamped by means of heavy end plates and secured by studs or rivets. Generally rectangular or round poles are used for these alternators. The round pole and the rectangular pole are shown in Figure 4. The advantages of using round poles compared to rectangular poles are: (i) The length of mean turn of the field winding is reduced, resulting in saving of copper material and reduced copper losses in the field winding. (ii) Ventilation is much improved, because the surface of field winding in uniformly exposed to air.

Design, Construction and Testing of Generator for Hydropower Plant

The type of the stator for Synchronous generator and Induction generator is same but the rotor type is different. The rotor of the Induction generator is shown in Figure 1. And the rotor of the Synchronous generator is shown in Figure 2.

Design, Construction and Testing of Generator for Hydropower Plant

444-04 (iii)

With round poles, circular field coils are used, which are not deformed by centrifugal forces. However, round poles should be used only in case poles are massive. In case this is used bulging out of field coil under centrifugal force is prevented by placing distance blocks in between the field coils.

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Design of Synchronous Generator

Design of electrical machines mainly consists of obtaining the dimensions of the various part of the machine to suit given specifications, using available material economically and then to furnish these data to the manufacture of the machine. The design flow chart is shown in Figure 5. The two design sheets are shown in Table 2 and Table 3. The aim of the designer is to obtain: (i) lower cost (ii) smaller size (iii) wider temperature limit (iv) lower weight (v) better performance under no load and loaded conditions (vi)

minimum losses

Design, Construction and Testing of Generator for Hydropower Plant

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Design, Construction and Testing of Generator for Hydropower Plant

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Design, Construction and Testing of Generator for Hydropower Plant

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Construction of 2 kVA Synchronous Generator

A suitable electrical machine is constructed after the design-calculation. The position of the generator is vertical because of direct-coupling with the hydraulic turbine. The turbine type is low-head propeller turbine and its speed is 1000 revolution per minute. Therefore, the total number of poles of generator is 6 poles to match with this turbine speed. In order to reduce the eddy current losses, the iron core for armature and salient pole rotor is laminated. The eddy current losses occur in all conductive materials with the electric flux-path of the rotating or varying magnetic field of the hydro-electric generator. The internal diameter of the stator is larger than the axial length of the stator core. Rectangular pole is used for 2 kVA salient pole generator. The procedure for construction of 2 kVA salient pole generator is divided into the following steps: (i) Stamping of circular iron-sheets (ii) Construction of armature (iii) Construction of salient pole type rotor (iv) Winding of armature and rotor

(1)

Stamping of Circular Iron-sheets

Firstly, the raw material for the iron core of armature and rotor are selected from the tank-sheets. These tanksheets are very low cost because they are waste materials. After the raw materials are selected, the circular iron sheets are stamped according to the design data as shown in Figure 6.

(2)

Construction of Armature

After stamping the iron sheets, the armature core is constructed according to the design data. The materials which are used for iron core are divided into two portions as the base or lower portion as die and the upper portion as a punch. The die and punch for armature core are accommodated at the 30 tons pressmachine. The die is shown in Figure 7. And the punch is shown in Figure 8.

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After that, the circular iron sheets are placed near the press-machine. These circular iron sheets are put into the die as shown in Figure 10. Then, the armature cores are punched by the punch as shown in Figure 11. Similarly, each of the circular iron sheets is punched. Before forming, iron sheets are purified by dilute nitric acid.

Design, Construction and Testing of Generator for Hydropower Plant

Then, the die and punch are assembled as shown in Figure 9. Care must be taken to adjust the alignment of the die and punch at the press-machine. It is also needed to fit the bolts and nuts firmly.

Design, Construction and Testing of Generator for Hydropower Plant

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(3)

Construction of Salient Pole Type Rotor

The iron core for salient pole type rotor is stamped according to the design data. After the punching of armature, the assembly of the die and punch of the armature are removed from the press-machine. And then, the assembly

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of the die and punch for salient pole rotor is fitted at the press-machine. The die for rotor core is shown in Figure 12. And the punch for rotor core is shown in Figure 13.Then, the die and punch for rotor is fitted at the press machine. Putting the circular iron sheets onto the die is shown in Figure 14.And rotor iron cores after stamping is shown in Figure 15.

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After stamping by press machine, rotor iron cores (laminated iron sheets) are purified by dilute nitric acid.

(4)

Winding of armature and rotor

Firstly, the insulation papers are inserted into the armature slots and the armature winding is accommodated in the armature slots as shown in Figure 16. Finally, the armature conductors are covered by insulation papers and varnish. Then, the copper wires for salient pole rotor are wound according to the design data. The winding type is lap and double-layer winding. The standard wire gage (S.W.G) No. 22 of round copper wire is selected for armature winding and standard wire gage (S.W.G) No. 21 round copper wire is selected for salient pole rotor winding. These wire gages are selected based on the current density and the current rating of the armature and salient pole rotor respectively.

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(5)

Performance Testing

After the construction of hydro-set, it is tested .Pumped-back system (or) water recycle system is used as water– resource. The constructed hydro-set is placed in the spiral casing of the turbine. All other necessary parts are prepared for performance testing. After the preparation is completed, the performance testing is started. Firstly, the water is delivered into the intake canal as shown in Figure 18. The inlet water is entered into the guide vane rings. The outlet from the water turbine is passed through the draft tube and reached into the lower pond. And then, the water is pumped back into the intake canal. The propeller runner is rotated horizontally. The speed of the propeller runner is increased and the speed of the generator is also increased.

Design, Construction and Testing of Generator for Hydropower Plant

Finally, the constructed generator is shown in figure 17.

Design, Construction and Testing of Generator for Hydropower Plant

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Testing with Domestic Lighting

Then, the output terminals of the generator are connected with the electrical board. 1000W halogen lamp and 500W halogen lamp are accommodated in the main switch board. Another type of load is chosen as 40 W fluorescent lamps. Total number of these lamps is 10 and the total power of these lamps is 400W. The frequency meter, voltmeter and an ammeter are also existed in the main switch board. Testing with 1400 W load is shown in Figure 20. The speed of the generator is measured with r.p.m meter at 1000W, 1400W and 1900W as shown in Figure 19 and the results are shown in the following Table 4.

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(ii)

Testing with Inductive Load and Lighting Load

The constructed generator is also tested with inductive load and lighting load. The inductive load is

¾

H.P

induction motor and the lighting load is 1000W halogen lamp. Therefore, the total connected load is approximately 1.6 kW which is the full load of the constructed generator. Then, the switch of the 1000 W halogen lamp is opened and the speed, voltage and the current are measured. Testing with 1000 W is shown in Figure 20. Consequently, the switch of the ¾ H.P induction motor is on and its ratings are measured. The results are shown in Table 6.

Design, Construction and Testing of Generator for Hydropower Plant

Moreover, the voltage rating, the current rating and frequency ratings are measured at three power rating of electrical loads. The results are as shown in the following Table 5.

Design, Construction and Testing of Generator for Hydropower Plant

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Conclusion

There are some problems of supplying power to rural and hilly regions by national grid system such as (i) expensive, (ii) difficult to maintain and (iii) un-economical. Laying transmission lines across such rural and hilly regions posses a great problem because of long distances of be covered and the existence of hills, mountains, ridges, valleys, etc. the project becomes extra-ordinarily costly. The maintenance of these lines is a tough job in view of frequent occurrence of storms, snow falls, land slides, ice formations etc. for such hilly isolated regions. Diesel-generating sets are not preferable because of high transportation cost of fuel for such mountain areas. In hilly regions energy situation in terms of availability and demand is very different form that in the urban areas. It is un-economical due to poor load. Renewable energy becomes favorable because of the above mentioned difficulties for rural and hilly regions. Amongst the renewable sources, hydro power occupies an important place for rural electrification. Therefore, it is an urgent need to construct the small-scale hydropower project in the rural and hilly regions. Rural and hilly areas with the renewable hydropower resources (river, waterfall, stream and creeks) should construct hydro power plants by means of self-reliance. To uplift the quality of life of villagers, 1.6 kW project can be constructed in rural areas with the small scale hydropower resources. 1.6 kW Pico-hydro power project is the pilot (or) pioneer plant. It can generate electricity required to develop the rural and hilly areas.

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References Alternate Hydro Energy Centre.2003.International Training Course on Small Hydropower Development . Roorkee,India: Indian Institute of Technology. Deshpande, M.V.1996. “Elements of Electrical Power Station Design”. College of Engineering Amravati.London: Sir Isaac Pitman & Sons, Ltd. European Small Hydropower Association. 2002.How to Develop a Small Hydro Site.Layman’s Guidebook. Gerard, Geoffrey.1949.Hydro-Electric Engineering. London: Sir Isaac Pitman & Sons, Ltd. Harvey,Adam.1998.Micro-hydro Design Manual. UK: International Technology Publications. Japan International Cooperation Agency. 1999. Hydro-Electric Power Engineering. Japan: Tanaka Hydraulic Machinery Works, Co., Ltd. Power Paul. 2004. Low Head Micro-hydroelectric Generators. Power Paul Company Limited. Rajput, R.J.1993. Electrical Machines. New Delhi: Tata Mc. Graw-Hill Company Limited. V.N.Mittle and A. Mittal .2000.Designof Electrical Machines. Delhi : Standard Publishers Distributors

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