The difference between inverter demagnetization and jump extinguishing excitation switch demagnetiza

First, the principle is different.

1. Inverter demagnetization: using the inverter working state of the three-phase full-control bridge, the control angle is less than 90 ° of the rectifier operation state, and suddenly retreats to a certain appropriate angle greater than 90 °, at this time, the excitation current changes the polarity, and is added to the excitation winding in the form of back EMF, so that the rotor current is rapidly attenuated to zero.

2. Jump out excitation: the power unit provides excitation current to the rotor of the synchronous generator; The excitation regulator, on the other hand, controls the output of the excitation power unit based on the input signal and the given regulation criteria.

3. Switch demagnetization: a switch used to quickly reduce the current in the excitation circuit.

Second, the characteristics are different.

1. Inverter demagnetization: because there is no contact, no arc ignition, and no large amount of heat is generated, the demagnetization is reliable.

2. Jump out excitation: It affects the stability of the generator, and the stability of the large-capacity unit during operation is very important for the stability and safety of the overall power grid.

3. Switch demagnetization: good flow performance: small contact resistance, low operating temperature rise, large short-term overflow; High dielectric strength; mechanical action spirit; Excellent overall performance.

Third, the role is different.

1. Inverter demagnetization: the excitation current changes the polarity and is added to the excitation winding in the form of back EMF, so that the rotor current is rapidly attenuated to zero.

2. Jump out excitation: maintain the generator terminal voltage at a given value, and when the generator load changes, the generator terminal voltage is constant by adjusting the strength of the magnetic field; Reasonable distribution of reactive power between parallel operating units.

3. Switch demagnetization: in the case of generator accidents, the jump demagnetization switch is used to quickly demagnetize; Disconnect the demagnetization switch during overhaul to form an obvious disconnection point.

What is the main difference between inverter demagnetization and jump excitation switch demagnetization?

Answer: If the generator uses the full control bridge for inverter demagnetization, the minimum inverter angle must be greater than the sum of the converter angle and the thyristor off angle, and the jump excitation switch is quickly shut down when the corresponding relay device detects that a certain value exceeds the load setting value range.

Function: Turn on and cut off the excitation current, and at the same time turn on the demagnetization resistor and put it into the demagnetization circuit when disconnected to prevent overvoltage.

Principle: when the generator is shut down and the motor outlet switch is broken, because there are some loads with the original annihilation, at this time, if the coarse rotor is changed, there is a larger working current than the no-load excitation current, when the switch is disconnected, all the excitation current and the increase in the speed of the steam turbine caused by the disconnection of the external load, these two parts are all used to establish the voltage, so that the voltage of the generator is higher than the rated voltage, and the generator will be out of the slag when the demagnetization switch is not put in, so that the winding will be electrically broken.

Demagnetization refers to the demagnetization system, which is to reduce the magnetic field energy in the rotor windings of the generator to a minimum as soon as possible. Of course, the simplest method of demagnetization is to disconnect the excitation winding of the generator rotor from the power supply, but the excitation winding is a large inductance, and if it is suddenly disconnected, it will cause a high overvoltage at both ends of the excitation winding, which will endanger the insulation of the rotor, so it is inappropriate to use the method of disconnecting the power supply of the rotor circuit to demagnetize.

Excitation, which should be excitation, is a machine that provides stator power to the stator of a generator or synchronous motor and provides a working magnetic field for generators and other electrical equipment (electrical equipment that works using the principle of electromagnetic induction).

This should be the start-stop process of the excitation starting system, which is usually used for the start-stop process of ultra-high-power motor starting device and excitation cabinet.

The function of the demagnetization switch is to turn on and cut off the excitation current, and at the same time turn on the demagnetization resistance and put it into the demagnetization circuit when disconnected to prevent overvoltage.

Principle: When the generator is shut down and the motor outlet switch is broken, because there are some loads in the original, the rotor also has a working current that is larger than the no-load excitation current, when the switch is disconnected, all the excitation current and the increase in the speed of the steam turbine caused by the disconnection of the external load, these two parts are all used to establish the voltage, so that the voltage of the generator is higher than the rated voltage, and the generator will have overvoltage when the demagnetization switch is not put in, so that the winding will be electrically brokendown.

First, in the case of generator accidents, the jump demagnetization switch is used to quickly demagnetize;

Second, disconnect the demagnetization switch during maintenance to form an obvious disconnection point.

The key to achieving these two functions is to quickly dissipate the energy of the generator's magnetic field** into heat). At present, it is widely used at home and abroad to shift the energy type demagnetization switch, which quickly transfers the excitation current and magnetic field energy to the demagnetization resistance during demagnetization, and basically does not absorb energy. Generally, there is no need to disconnect the demagnetization switch after the shutdown, because the normal shutdown is to change the trigger angle of the thyristor by the automatic excitation regulator for inverter demagnetization.