Demagnetization Method of Diesel Generator Set

Do you know what the demagnetization method of diesel generator set is? First, inverter demagnetization, using the inverter working state of the three-phase fully-controlled bridge, the control angle is changed from the rectification operation state of less than 90°, to the rectification operation state of less than 90°, and suddenly retreats to the state of greater than 90°. At an appropriate angle, the excitation power changes its polarity and is applied to the excitation winding in the form of back EMF, so that the de-excitation process of the rotor current rapidly decaying to zero is called inverter de-excitation. This de-excitation method quickly feeds back the stored energy of the rotor to the AC side power supply of the three-phase fully-controlled bridge, without the need for discharge resistors or arc extinguishing grids, and is a simple and practical de-excitation method. Because there is no contact, no arc, and no large amount of heat is generated, the demagnetization is reliable. The larger the back EMF, the faster the demagnetization speed.

The back EMF generated during the inversion of the three-phase fully-controlled bridge is proportional to the power supply potential of its AC side, so the value of the back EMF is limited to a certain extent. ), which also reduces the back EMF to a certain extent. Therefore, independent inverter de-excitation is limited by the voltage of the AC power supply. During inverter de-excitation, although the excitation current drops linearly, the value of the back EMF applied during inversion is smaller than that of the arc-quenching method, so the current decays. The rate is small, the demagnetization time is relatively long, but the overvoltage multiple is also very low. Non-linear resistance de-excitation is the normal shutdown of the excitation system, the regulator automatically inverter de-excitation; accident shutdown, tripping the de-excitation switch to transfer the magnetic field energy to the energy-consuming resistance de-excitation.

When the diesel generator set is in an abnormal operating state such as pole sliding, a high induced voltage will be generated in the rotor circuit. At this time, the rotor overvoltage detection unit A61 module installed in the rotor circuit will detect the rotor forward overvoltage signal. , immediately trigger the V62 thyristor element, incorporate the energy dissipation resistance unit FR into the rotor circuit, and eliminate the generated overvoltage energy through the energy absorption effect of the energy dissipation resistor; and the reverse overvoltage signal of the rotor circuit directly passes through the V61 The diode is connected to the energy dissipation resistor to absorb energy to ensure that the rotor of the diesel generator set will never be open, thereby reliably protecting the rotor insulation from damage. Due to the existence of this protection, the rotor winding will generate an opposite magnetic field to offset the reverse magnetic field generated by the negative sequence current of the stator, so as to protect the rotor surface and the rotor guard ring from burning out.

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