R448AVR excitation control of over current protection
For R448AVR excitation control device, may have the following a few reasons, through the rectifier bridge arm element, and the excitation current of transformer winding more than its normal rate.
1) R448AVR excitation control device breakdown inside a bridge rectifier bridge arm short circuit, loss of ability to block, the ac power can be damaged short circuit of bridge arm and other components, intact bridge arm alternately formed two phase short circuit and three-phase short circuit.The current will flow through some intact bridge arm unit and transformer winding, its value can be more than three phase short circuit when the ac amplitude of periodic components.
2) rectifier bridge connection by the rotor excitation winding circuit may be flying arc short circuit, two rotor winding grounding, dc bus short-circuit fault, such as between the dc short-circuit fault current flows through the same some components and transformer winding bridge arm, R448AVR excitation control value also can be large.
3) all control R448AVR excitation control rectifier bridge in inverter working state, because of the small inverter Angle beta disappear or ac power supply voltage, caused disappear or trigger inverter commutation failure, rotor winding of bridge arm components through short circuit through a stream, make these components through the bridge arm than normal working current and long duration.
4) SCR control mistakenly triggered by external disturbance signal, or loss of pulse and single-phase conduction, or limited link failures make the thyristor control Angle is too small, the current through the silicon components could make greater than work values.
For these cases, usually adopt overcurrent protection measures, will be limited by silicon components of current quickly, or to cut off the fault current in time, avoid silicon p-n junction temperature is too high and damage.In general rectification device with overload and short circuit protection is as follows:
In R448AVR excitation control dc fast switch installed in dc side, its action time of about 10 ms, its main function is to cut off the fault current of the dc side, protect the rectifier device and avoid fuse in dc side of the rectifier element short circuit occurs when fusing.When failure occurs within the rectifying device, dc rapid switch to this device can not be effective and protective effect, only the parallel operation of other rectification device is internal fault protection.