3BHE024855R0101 UFC921A101 New ABB ACS2000 Converter Circuit Board

Description

UFC921A101 is the most widely used UNITROL 5000 excitation system. Take my company as an example:
Switzerland ABB product, model: UNITROL 5000, self shunt static excitation system
The static excitation system of generator controls the excitation current through silicon controlled rectifier bridge to achieve the purpose of regulating the voltage and reactive power of synchronous generator.

UFC921A101 is mainly divided into four parts:
1. Excitation transformer;
2. Excitation regulator (AVR);
3. Silicon controlled rectifier;
4. Excitation and de excitation unit.
Excitation transformer
The excitation transformers are three single-phase epoxy cast dry-type transformers produced by Guangdong Shunte Electric Co., Ltd; The total capacity is 3X3300KVA; The transformation ratio is 27kV/1060V.
Natural air cooling (with cooling fan) is adopted. When the temperature of excitation transformer reaches 100 ℃, the cooling fan starts automatically; When the temperature drops to 80 ℃, the fan will stop automatically. When the temperature of excitation transformer reaches 130 ℃, an overtemperature alarm will be given.
Three sets of bushing CT are provided for each phase on the high-voltage side, two for protection and one for measurement. Each phase at the low-voltage side is also provided with three sets of CT, two for protection and one for measurement.
Automatic voltage regulator AVR
The main function of automatic voltage regulator (AVR) is to accurately control and adjust the generator terminal voltage and reactive power. It can quickly respond to the excitation voltage with a response time of several milliseconds.
AVR selects dual channel system with manual emergency standby channel, which is the highest configuration of excitation system of UNITROL 5000 system at present.
Basic principle of AVR
It is mainly composed of three basic units: measurement comparison, comprehensive amplification and phase shifting trigger.
The measurement comparison unit is used to measure the converted DC voltage proportional to the generator terminal voltage, and compare it with the corresponding voltage setting value to obtain the deviation;
The voltage deviation signal is input to the comprehensive amplification unit, which plays a comprehensive amplification role in measuring and other signals;
The phase-shifting trigger unit changes the trigger pulse output to the silicon controlled rectifier and the conduction angle according to the change of the input control signal, so as to control the output voltage of the silicon controlled rectifier and regulate the excitation current of the generator.

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