A1-104 CIGRE 2012 Calculation of Electromagnetic Force on ...

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<strong>Electromagnetic</strong> force(N)200010000-1000-2000FrFt-30000 5 10 15 20Time(ms)b) The electromagnetic force <strong>of</strong> No.9 damping winding as time changesFig.7 The electromagnetic force distribution acting on damping windings under negative sequence operationC. The Different Damper Winding Connection FeaturesHydro-generator rotor has damping system within the magnetic poles, and the damping system are composed <strong>of</strong>article damping, damping ring, damping ring joint piece and other parts. According to the joint form <strong>of</strong> damping ring,the damping system is divided into the damping system and half damping system. The connection modes <strong>of</strong> circuit intwo different kinds <strong>of</strong> damping ring connection forms are shown in Fig.8.a) The half damping systemb) The absolute damping systemFig.8 The connection modes <strong>of</strong> circuit in two different kinds <strong>of</strong> damping ring connection formsThe damping system is that the damping ring is fixed through the core tighten screw and the damping ringbetween adjacent poles is connected through the connecting link. This structure design makes the parallel dampingbars within the individual pole connect with other damping bars in other poles together. The half damping system is
that when the damping ring is fixed in each pole, it will not connect with other damping rings in adjacent poles. Thisstructure design makes the damping bars in a pole only mutual parallel itself.The rated operation and negative sequence operation researched above mainly researched on the half dampingsystem. When the generator adopted the absolute damping system in negative sequence operation, the calculationresults were as follows. The magnetic field and eddy current in damping winding <strong>of</strong> the absolute damping system wereshown in Fig.9.a)Magnetic field in damping windingsb)Eddy current in damping windingsFig.9 The magnetic field and eddy current in damping winding <strong>of</strong> the absolute damping systemIt could be seen from Fig.9 that the No.1 damping winding had the highest magnetic flow density and the otherswere less. The eddy current density in the No.1 damping winding was bigger than the others. Fig.10 showed theelectromagnetic force distribution acting on damping windings.From Fig.10 a), it could be seen that along the rotor rotation direction the electromagnetic force <strong>of</strong> the first dampingwinding (1 # damping winding) was significantly greater than the rest <strong>of</strong> the damping windings. Meanwhile, thetangential magnetic force <strong>of</strong> the No.1 damping winding was greater than the radial electromagnetic force <strong>of</strong> the No.1damping winding. From Fig.10 b), it indicated that the electromagnetic force <strong>of</strong> the No.1 damping winding whichsuffered the largest force would fluctuate in a time period, because <strong>of</strong> the harmonic current in damping winding. Theradial electromagnetic force and the tangential electromagnetic force played respective role at different time.2000<strong>Electromagnetic</strong> force(N)0-2000-4000FrFt-60000 2 4 6 8 10Damping winding numbera) The electromagnetic force <strong>of</strong> the No.1 damping winding<strong>Electromagnetic</strong> force(N)Fr0.5Ft0-0.5-10 5 10Time(ms)15 201 x <strong>104</strong>b) The electromagnetic force <strong>of</strong> the No.1 damping winding as time changes
Page 4 and 5: )Eddy current in damping windingsFi
Page 8: Fig.10 The electromagnetic force di

A1-104 CIGRE 2012 Calculation of Electromagnetic Force on ...

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