Thyristor Starter Switching Speed for Fault Current Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Thyristor starters face damage from fault currents during commutation operations due to short-circuit failures in thyristors, leading to potential damage to sound thyristors and armature windings, with the severity increasing with fault current magnitude and duration.
Innovation Solution
A thyristor starter system that adjusts the switching rotation speed based on the inductance of the synchronous machine to minimize fault current duration and magnitude, employing a configuration with a converter, DC reactor, and inverter, along with controllers to manage firing phases and current output, thereby reducing component damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thyristor starter uses six thyristors in the inverter for commutation operation, then the synchronous machine can be started and driven at a predetermined rotation speed, but a short-circuit failure in any thyristor causes fault current to flow through sound thyristors and armature windings, leading to component damage
Solution Approach 1:
The control system performs preliminary detection of thyristor health status before fault current can cause damage. By monitoring voltage across each thyristor and detecting abnormal voltage patterns that indicate short-circuit failures, the system identifies faulty thyristors before they can propagate fault current to other components.
Solution Approach 2:
The control system continuously monitors the voltage across each thyristor during commutation operation and uses this feedback to detect short-circuit failures. When abnormal voltage indicating a fault is detected, the control system responds by adjusting firing signals to prevent fault current from flowing through sound thyristors and armature windings.
2Reliability
If the fault current magnitude and conducting time increase, then the damage to components such as sound thyristors and armature windings becomes greater, but the control system must respond quickly enough to prevent excessive damage
Solution Approach 1:
The control system uses real-time voltage monitoring feedback across each thyristor to detect short-circuit failures immediately when they occur. This continuous feedback enables the control system to identify faulty thyristors and adjust firing signals without delay, minimizing the conducting time of fault current and reducing damage to components.
Solution Approach 2:
The control system replaces mechanical or passive protection methods with an active electronic control approach. By using electronic voltage detection and control signal adjustment, the system achieves faster response times compared to traditional protective devices, thereby reducing fault current conducting time and minimizing component damage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively suppresses damage from fault currents by shortening the conducting time of fault currents, regardless of the synchronous machine's inductance, thus protecting components and ensuring reliable operation.
Implementation Method 1
a converter for converting AC power into DC power
Implementation Method 2
a DC reactor for smoothing DC power
Implementation Method 3
an inverter for converting DC power applied from the converter through the DC reactor into AC power with a variable frequency
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A thyristor starter (100) is configured to accelerate a synchronous machine (20) from a stop state to a predetermined rotation speed by sequentially performing a first mode of performing commutation of an inverter (2) by intermittently setting DC output current of a converter (1) to zero and a second mode of performing commutation of the inverter (2) by induced voltage of the synchronous machine (20). In a first case in which a first synchronous machine having a first inductance is started, a switching rotation speed for switching from the first mode to the second mode is set to a higher rotation speed, compared with a second case in which a second synchronous machine having a second inductance larger than the first inductance is started.