Load increasing speed and power factor of MTU diesel generator set

The increasing speed of generator load after grid connection should be determined according to unit capacity, hot and cold state and actual operation. If the temperature of the stator winding and stator core exceeds 50% of the rated temperature, the generator can be considered to be in the hot state; if the temperature of the stator winding and stator core is lower than 50% of the rated temperature, the generator can be considered to be in the cold state. After the turbogenerator is connected to the power system from the cold state, the stator can normally carry 50% of the rated current immediately and then rise to the rated value at an even rate within 30 minutes. According to the relevant data, the time required for the stator current of 12MW generator set from 50% to the rated value is about 37 minutes.

The reason for limiting the increase rate of generator load is to prevent residual deformation of the rotor windings. Because the rotor rotates at high speed, the huge centrifugal force will press the rotor windings tightly on the slot wedges and collar of the rotor core, forming a whole that cannot move relatively. When the rotor is heated, the expansion of the winding copper rod is greater than that of the iron core, but it can not move freely. Therefore, the copper rod is relatively compressed and deformed. When the compression stress exceeds the elastic limit, residual deformation will occur. When the generator is shut down and cooled, copper will shrink more than steel, which will cause insulation damage, and the tank bottom is the most severe. Every time after a start, stop, this phenomenon is repeated, residual deformation gradually accumulated, will likely cause inter-turn short circuit or grounding fault. "Regulations" regulation, therefore, the stator current from 50% (according to the calculation, the sudden increase load is less than 50% of the rated current, rotor winding won't produce residual deformation) to 100% rated current needed time, on the other hand, when the generator in the hot state or accident cases, incorporated into the power system to increase the speed of load is not restricted.

The generator's power factor cos φ, also known as force ratio, is the cosine of the phase Angle between the stator voltage and the stator current. It shows the relationship between the active power, reactive power and apparent power emitted by the generator. Its size reflects the output of reactive load from the starting motor to the system. The reactive load sent by the generator is usually inductive, and the rated power factor of the general generator is 0.8.

The power factor of the generator varies from the rated value to 1.0 and the rated output can be maintained. However, in order to maintain the stable operation of the generator, the power factor should not exceed late phase 0.95, generally operating at 0.85.

When the power factor is below the rated value operation, the generator output should be reduced. The lower the power factor is, the larger the reactive power component of the stator current is, and the stronger the demagnetization armature reaction is. At this time, in order to maintain the constant voltage of the generator, the rotor current must be increased, and the stator current of the generator also increases due to the increase of the reactive power component. If you want to keep the output of the generator unchanged, it will make the rotor current and stator current of the generator exceed the rated value, and the rotor temperature and stator temperature exceed the allowable value and overheating. Therefore, in the operation of the generator, if the power factor is lower than the rated value, attention must be paid to adjust the load so that the rotor current does not exceed the allowable value.

Jiangsu Meiao Power Technology Co., Ltd. is an important manufacturer of diesel generators. Us ao-generator set manufacturers mainly manufacture and sell diesel generator sets, the power of generator sets is 3-3000KW, mobile station is 24-600KW, Marine emergency diesel generator set 24-800KW, gas generator set, heavy oil generator set and all kinds of imported series, special series (trailer, silent speaker, mobile lighthouse, container, etc.) diesel generator Group at the same time engaged in generator set maintenance and generator set accessories after-sales service.