Three-phase synchronous generator in the composition and working principle of

Three phase synchronous generator composed of a prime mover driven DC excitation of synchronous generator rotor, with the speed of n (RPM ) rotation, according to the electromagnetic principle, three-phase stator winding is induced AC voltage. The stator winding to access electricity load, motor with AC power output. If the circuit is not saturated, then the armature MMF and magnetic potential each produce the corresponding flux, and the stator winding internal sense because of potential. For a motor, armature magnetic potential the induction electric potential can be expressed as Ea=-jIaXa. Xa is called the armature reaction reactance. Xa+X σ=Xs non-salient pole synchronous generator synchronous reactance. For salient pole motor, because the straight shaft. Shaft resistance, armature MMF can be decomposed into Fad and Faq respectively. They are Induction EMF are written as Ead=-jIdXad and Eaq=-jIqXaq, type Xad.Xaq are direct axis and axis armature reaction reactance. Xad+X σ=Xd.Xaq+Xσ =Xq, Xd and Xq respectively direct axis synchronous reactance and quadrature axis synchronous reactance. X σfor magnetic leakage flux caused by reactance. Synchronous reactance of synchronous motor performance is an important parameter, through open experiment and steady-state experiments can be obtained.

Synchronous generator no-load characteristics is a very important characteristic, it directly affects the motor characteristics, through an open experiment can also be found in excitation system fault. State of short circuit characteristic and zero power factor characteristic are the important characteristics of synchronous motor, and no-load characteristics matching, can find out the synchronous generator state parameters and determine the exciter armature current compensation.

Synchronous generator external characteristic curve is used to calculate the motor operation is one of the important indexes and voltage regulation rate.

Synchronous generator regulation characteristic can make the operation staff know the power factor is constant, does not change the terminal voltage value. The load current to the many small and not make the field current exceeds a specified value.

The national standard" GB1029" of a three-phase synchronous motor experiment method to make specific provisions, apply to ordinary3-phase synchronous generator type test or examination experiment. Through the experiment to determine the motor each performance index. A variety of motor efficiency and voltage regulation are in the standard of the corresponding technical conditions are specified, the experimental results and the standard data can determine the quality and performance of a synchronous generator.

If thou take rated excitation current and voltage change rate, usually used for graph method, with the national standard GB1029are introduced, the specific steps are as follows:

(1) as shown in Figure1is drawn on the open circuit characteristic curve, and along the longitudinal axis of rated voltage phasors UN.

(2) the origin of O rated armature current phasor IN,Φ N angle to the longitudinal axis ( COS ΦN rated power factor ).

(3) from the phasor UN terminal to the armature winding resistance drop INRa parallel and vector, IN, Ra as the benchmark when the operating temperature of the winding resistance ( for large motor Ra is negligible, the small motor into the feasible practical measurement ), from the INRa terminal as a perpendicular to the phasor IN Potier electric pressure drop phase

INXp ( Xp Potier reactance voltage phasor calculation method of INXp ( Xp see below (5), UN and INRa and

And INRa and INXp phase and phase of Ep, Ep and UNδangle.

(4) by the open circuit characteristic identification corresponding to the excitation current of Ifp in Ep phase terminal and longitudinal

With the longitudinal axis ofδ +Φ N angle phasors Ifa

(5) rated armature current of armature reaction of the excitation current of Ifa and Xp determine Potier reactance:

If the right below the open circuit characteristic curve, and on the map in the F, F point ordinate at rated voltage, the abscissa zero power factor characteristic corresponding to rated armature voltage rated armature current excitation current is passed through the F for horizontal axis parallel to the straight line CF, CF length equivalent to the three-phase steady state short characteristic curve corresponding to the rated armature current excitation current of Ifk, since C as a straight line parallel to the straight part of the open circuit characteristic in the open circuit characteristic to H, from CF CF to K vertical HK, line segment

The length of HK is rated armature current in the Potier reactance voltage drop current on Xp△ Up, then the Potier

Reactance Xp, can be calculated by the following equation.

Xp = Up / IN

If the per-unit value drawing open circuit characteristic curve, then, can be obtained directly. The length of a line segment representation corresponds to the excitation current.

? (6) and the vector and is rated excitation current.

(7) by the open circuit characteristic curve of corresponding and open circuit voltage. Voltage change rate of press machine

△ U= ( U0-UN ) /UN*100

Note: the laboratory for experimental teaching by the synchronous motor is usually small.

< a > generator overview

The generator is converted to other forms of energy into electrical energy machinery and equipment, which is composed of turbine, steam turbine, diesel or other power machinery drive, water, air, fuel combustion or nuclear fission energy into mechanical energy to pass generator, the generator is converted to electrical energy. Generators in the industrial and agricultural production, national defense, science and technology and daily life in a wide range of uses.

The generator form a lot, but the working principle is based on the law of electromagnetic induction and electromagnetic force law. Therefore, the structure is a general principle : use appropriate magnetic and conductive material to each other in the electromagnetic induction circuit and the circuit, to generate the electromagnetic power, achieve the purpose of energy conversion.

The generator has been the implementation of export product quality permit system, did not obtain a license of export quality products are not allowed to export.

< two > generator classification can be summarized as follows:

Generator: DC generator and the AC generator

Alternator: synchronous generator and induction generator ( rarely used )

AC generator can also be divided into single phase generator with a three-phase generator.

< three > generator structure and working principle

Generator stator, rotor, usually by the end cover and bearing components.

The stator consists of a stator iron core, coil winding machine, and the fixation of these parts of the other structural components.

The rotor comprises a rotor iron core ( or magnetic, magnetic yoke ) winding, retaining ring, ring, ring, a fan and a rotary shaft and other components.

By bearing and end cover of the generator stator, rotor connected together, so that the rotor can rotate in a stator, to cut magnetic force lines, thereby to generate induced electromotive force, led out through a connecting terminal, connected to the circuit, they generate electricity.

The working principle of diesel generator

Diesel driven generator, diesel energy into electrical energy.

In the diesel engine cylinder, after the air cleaner filtered clean air and nozzle ejecting pressure atomized diesel are fully mixed, in the piston upward pressure, reduced volume, temperature rises rapidly, reaching diesel ignition. Diesel fuel is ignited, mixed gas burning, the volume of rapid expansion, pushing the piston downward, known as the ' work '. Each cylinder according to a certain sequence of work, on the piston thrust through the connecting rod to drive the crankshaft strength, so as to drive the crankshaft.

The brushless synchronous AC generator and diesel engine crankshaft mounted coaxially, can use diesel rotary drives the rotor of the generator, using the ' induction ' principle, generator can output the induced electromotive force, the closure of the load circuit can produce electricity.

Here only to describe the basic principle of generating unit. To be usable, stable power output, we also need a series of diesel engine and generator control, protection devices and circuits. Detailed in gasoline generator principle.

Petrol engine driven generator, fuel energy into electrical energy.

In a gasoline engine cylinder, mixed gas burning, the volume of rapid expansion, pushes the piston down to work. Each cylinder according to a certain sequence of work, on the piston thrust through the connecting rod to drive the crankshaft strength, so as to drive the crankshaft. The brushless synchronous AC generator and the crankshaft of the gasoline engine is coaxially mounted, can use gasoline engine rotation drives the rotor of the generator, using the ' induction ' principle, generator can output the induced electromotive force, the closure of the load circuit can produce electricity.