How does the rectifier cabinet work?
A rectifier cabinet is a power device used to convert alternating current into direct current. The rectifier cabinet adopts the same-phase anti-parallel three-phase bridge rectifier circuit structure.
The working principle of the rectifier main circuit in the rectifier cabinet is to reduce the voltage of the high-voltage AC power provided by the high-voltage power supply network through the voltage regulating transformer and the on-load tap-changer, and then reduce the voltage by the rectifier transformer. , convert the AC power into DC power, and provide DC current for the process electrolyzer to meet the load's requirements for DC power.
In the whole transformation process, the step-down regulating transformer and the on-load tap-changer mainly complete the step-by-step regulation of the AC voltage, that is, the coarse regulation.
In order to ensure the average power factor of the grid side operation, the rectifier cabinet meets the requirements of the power supply department for power users. The diode rectifier is an AC current controlled current saturation reactor that controls the PWM output, and corrects the AC current to a DC current, realizing the fine-tuning of the DC current and the power factor to meet the current needs of the size and current stabilization during the electrolysis process.
For a three-phase bridge rectifier circuit, when the on-load offset switch is in a certain position, the output voltage of the rectifier transformer is U2, and the output DC voltage of the rectifier transformer is UD=1.35·U2·cosα. When the equivalent resistance of the electrolytic cell load is Rd When , according to Ohm's law, the DC current of the entire DC circuit id=UD/Rd=1.35·U2·cosα/Rd. The adjustment function of the saturable reactor is to adjust the saturation angle by controlling the winding current to change the core magnetic flux density α, so the load tap switch is used to adjust U2, and the PWM controller is used to adjust cosα. When the rectifier unit operates in a current closed loop, current fluctuations will occur due to changes in the power grid and load. Through the automatic control of the saturable reactor current, the stability of the DC output current when the unit is disturbed is realized.
The role of the rectifier cabinet:
1. The function of the rectifier cabinet is to supply the rotor current of the motor after the 100HZ three-phase alternating current from the main exciter is rectified by its three-phase full-wave bridge type. In order to ensure the reliability of the generator rotor current, two or three rectifier cabinets are generally provided. in normal operation. in parallel operation.
2. Convert the three-phase AC voltage output by the excitation transformer into DC voltage (using three-phase bridge rectification).