Generators

Characteristic and performance analysis of main parts of generator

Stator:

Stator consists of base, stator core and stator windings.

The base is welded by steel plate, the structure is light and sturdy, and the base is divided into many air inlet and outlet zones in the axial direction;

Stator coil:

It is stacked by strands of copper wire covered by polyester glass fiber, with half-unit type and basket shaped structure (parts of stator coils use transposition structure). The insulation grade of the stator coil is F grade. The stator coil is shaped by continuous wrapping and mould pressing with mica tapes. The coil end is firmly tied up to the support and the bundling ring with unidirectional tapes or dacron-glass ropes thus the turbo-generator unit became highly resistant towards sudden short-circuit conditions.  

Stator core:

Stator core is punched and stacked by cold rolled non-oriented, high permeability, low loss high-quality silicon steel sheet, both sides of the silicon steel sheet are coated with a solid insulating film to prevent short-circuit between the stator core pieces to reduce eddy current loss.

Rotor:

The rotor is composed of shaft, coil, center ring, shroud ring and fan ring etc. The rotor coil is made of cold-drawn flat copper wires, and processed by oxygen-free annealing. The rotor coil of generator with 50MW and above is welded together by silver-bearing cold-drawn copper wires and adopts F grade insulation.

The shroud ring at rotor coil end is made of non-magnetic steel. Both ends of the rotor are equipped with centrifugal fan or axial flow fan with paddle fan blade which is forged by high-strength aluminum alloy.

Rotor machining:

The generator shaft is forged from an integral high-quality alloy steel and has an axial groove formed thereon for fitting a rotor coil and an air groove or a crescent groove is made in the large tooth to enhance the cooling of the main body and the coil end. The slots are processed by special machine for generator rotor processing, Tacchi high precision horizontal slotting and milling machine made in Italy, to ensure the high efficiency of generator.

The generator rotor must be subjected to high-speed dynamic balancing experiment and dynamic impedance experiment before delivery to verify the mechanical strength of the rotor and ensure excellent inter-turn insulation of the rotor windings.

(2)Model

   Mainly produce the following model steam turbine generator and the specifications are as follows:

Voltage(KV) Frequency(HZ) Power(MW)

2 poles steam turbine generator 6.3-3.8 50 3-60

6.6-13.8 60

4 poles steam turbine generator 0.4/0.69 6.3/6.6 10.5/11 50 0.5-30

0.4-11 60

QNP steam turbine generator uses closed-loop air self-circulation ventilation.

The rotors of turbo-generator under 50MW adopt indirect ventilation cooling method;

The rotors of 50MW and above turbo-generator is directly ventilated and cooled; an auxiliary groove is machined under the rotor winding trunking; air vents are machined on the rotor windings; with the action of the fan head and the centrifugal pressure head of the air vents, the rotor windings are directly cooled by air from the auxiliary groove and air vents.

(4)Excitation mode

   QNP's steam turbine generator can adopt static silicon controlled type, two-pole AC brushless excitation and three-pole AC brushless excitation, three kinds of excitation mode.

(5)Insulation system

   Adopt class F insulation materials and insulation structure, during the running time, assess the system according to class B insulation grade, meanwhile some margin has been kept.

(6)Design and acceptance criteria

    Design, manufacture, inspection are carried out according to the relevant national standards, at the same time can meet the International Electrotechnical Commission IEC34-1 latest standards. According to customer`s requirements, QNP`s steam turbine generator can also be designed, manufactured and accepted according to ANSI, NEMA and other international standards.

(7)Technical Performance Analysis

1.Output margin

    The series of steam turbine generator of QNP keeps 10% output margin.

2.Loss and efficiency

    The steam turbine generator of QNP optimized the design and farthest minimized the additional loss and wind abrasion of generator under no-load and short-circuit condition, improved the efficiency of the generator, in general, QNP steam turbine generator`s efficiency is 0.2% higher than domestic similar models in this industry. It is higher than the national efficiency standard on the same capacity level. For example: QNP 15MW steam turbine generator`s efficiency value can reach 97.65%, and the national standard value is 97%.

3.Running reliability

    QNP's steam turbine generator adopts advanced manufacturing technology, especially the rotor`s overspeed test uses high-speed dynamic balancer, rotor`s balance precision has been greatly improved, and the rotor`s vibration value is decreased. So that the steam turbine generator`s running availability factor has been improved, and the unit`s forced outage rate is decreased. At present, the availability factor of the steam turbine generator can reach about 99%, and the forced outage rate fell to 0.04% to 0.4%. Overhaul interval is up to 5 years. And the unit life can reach to 35 to 40 years.

Model meaning

    QFWD-3-2A

    QF Steam turbine generator

    W W means brushless, without W means static silicon controlled

    D D means double support, without B means single support

    3 Rated power

    2 2 means two poles and means the rated rotation speed is 3000 r/min

        4 means four poles and means the rated rotation speed is 1500 r/min

    A means the design serial number: A.B.C.D