Demagnetization Method and Function of 900kw Diesel Generator

900kw diesel generator, as a high-power generator set, has full power and strong power. At the same time, as a diesel generator set, it has the characteristics of simple operation and convenient maintenance. How much do you know about the demagnetization method and function of 900kw diesel generator?

 

The 900kw diesel generator becomes de-excitation.

Utilizing the inverter working state of the three-phase full-control bridge, the control angle is changed from the rectifying operation state of less than 90° to an appropriate angle greater than 90°. At this time, the excitation power is changed and applied to the excitation winding in the form of back EMF. , The de-excitation process in which the rotor current quickly decays to zero is called inverter de-excitation. This de-excitation method quickly feeds back the rotor energy storage to the AC side power supply of the three-phase full-control bridge, and does not require discharge resistors or arc extinguishing grids. It 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 greater the back EMF, the faster the demagnetization speed. The back EMF generated during the inversion of the three-phase full-control bridge is directly proportional to the voltage of the AC side power supply, so the value of the back EMF is limited to a certain extent. At the same time, the large control max (or small inverter angle min) is set to prevent "inverter subversion". The limitation of) also reduces the back EMF to a certain extent. Therefore, single inverter demagnetization is limited by the AC power voltage. During inverter demagnetization, the excitation current decreases linearly, but the applied back-EMF value during inverter demagnetization is smaller than that of the arc extinguishing grid demagnetization method, so the current attenuates The rate is small, the demagnetization time is relatively long, but the overvoltage multiple is also very low.

 

900kw diesel generator non-linear resistance demagnetization.

When the excitation system is shut down normally, the regulator will automatically demagnetize by inverter; if it is shut down by accident, the demagnetization switch will jump to transfer the magnetic field energy to the energy-consuming resistor to demagnetize. When the generator is in an abnormal operation state such as slipping, a very 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 and immediately Trigger the V62 thyristor element, integrate the energy dissipation resistor unit FR into the rotor circuit, and eliminate the generated overvoltage energy through the energy absorption of the energy dissipation resistor; and the reverse overvoltage signal of the rotor circuit directly passes through the V61 second tube The energy dissipation resistor is connected to absorb energy to ensure that the generator rotor will never open circuit, so as to reliably protect the rotor insulation from damage. Due to the existence of this kind of protection, the rotor winding will produce an opposite magnetic field, which can 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.

 

The role of 900kw diesel generator magnetoresistance.

The excitation winding of a 900kw diesel generator is a coil with a large inductance. Under normal conditions, the excitation current generates a strong magnetic field on the generator rotor. When the 900kw diesel generator fails internally, it is necessary to quickly cut off the excitation current and remove the magnetic field of the 900kw diesel generator to avoid the expansion of the accident. However, it is very difficult to use a switch to directly cut off the current in such a circuit with a relatively large inductance. Because directly cutting off the excitation current will generate high voltage at both ends of the excitation winding, which may burn the switch contacts. Therefore, before cutting off the excitation circuit, first connect the de-excitation resistance at both ends of the rotor in parallel, so that when the excitation circuit is cut off, the de-excitation resistance can quickly absorb the magnetic energy of the excitation winding, slow down the rotor current change speed, and reduce the rotor self The induced electromotive force plays the purpose of reducing the rotor overvoltage and demagnetization.

 

The de-excitation resistance is not when the 900kw diesel generator is paralleled or de-arranged, but when the 900kw diesel generator is used, the de-excitation resistor is input and placed at both ends of the rotor coil.The de-excitation switch is a switch used to quickly reduce the current in the excitation circuit. Before starting to build the voltage, put in the de-excitation switch. In the event of a 900kw diesel generator shutdown or accident, trip the de-excitation switch to cut off the excitation circuit current to achieve the purpose of quickly reducing the voltage of the 900kw diesel generator.

effect:

(1) It is to quickly cut off the 900kw diesel generator excitation winding and excitation power path.

(2) Quickly extinguish the magnetic field inside the 900kw diesel generator.

 

The above is the demagnetization method and function of 900kw diesel generator introduced by Dingbo Power. If you are interested in diesel generators, please contact Dingbo Powet by email. Dingbo Power will serve you faithfully.Our email is dingbo@dieselgeneratortech.com.