Thyristor Starter Phase Control During Commutation Transition
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Solution Overview
Problem
In thyristor starters, short-circuit failures during commutation operations in the inverter lead to fault currents that damage sound thyristors and armature windings, with the extent of damage increasing with fault current magnitude.
Innovation Solution
The thyristor starter employs a controller to manage the firing phase of the inverter, using two commutation modes: intermittent commutation at startup and load commutation as speed increases. During the transition from intermittent to load commutation, the phase control angle of the inverter is adjusted to reduce fault current by shortening its duration and magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the inverter performs commutation by firing thyristors in synchronization with rotation, then the synchronous machine can be accelerated to predetermined rotation speed, but fault current damages components when short-circuit failure occurs in any thyristor
Solution Approach 1:
The control method prepares the system for potential faults by implementing a specific phase control angle strategy during the critical transition period. Before fault can occur, the system adjusts the phase control angle to limit fault current magnitude, thereby preventing severe damage while maintaining normal acceleration functionality
Solution Approach 2:
The invention changes the phase control angle parameter dynamically during commutation. Specifically, during the first time period from start of second mode to arrival of induced voltage at first voltage value, the phase control angle is adjusted so that its value becomes larger as rotation speed becomes higher, which effectively limits fault current and protects components
2Object-affected harmful factors
If the phase control angle is adjusted to limit fault current, then component damage is reduced, but the control complexity of the inverter increases
Solution Approach 1:
The control system dynamically adjusts the phase control angle based on real-time operating conditions, specifically during the transition from first mode to second mode commutation. This dynamic adjustment is implemented through a controller that monitors rotation speed and induced voltage, automatically modifying the phase control angle to limit fault current without requiring complex manual intervention or additional hardware
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
This approach effectively suppresses damage from fault currents by reducing their magnitude and duration, particularly during the critical phase when the rotation speed is low, thereby protecting thyristors and armature windings.
Implementation Method 1
a converter that converts AC power into DC power
Implementation Method 2
a DC reactor that smoothes DC power
Implementation Method 3
an inverter that converts DC power applied from the converter through the DC reactor into AC power with a variable frequency
Implementation Method 4
a second mode of performing commutation of the inverter by induced voltage of the synchronous machine
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A thyristor starter (100) accelerates 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 the thyristor starter (100), during a first time period from start of performance of the second mode to arrival of the induced voltage of the synchronous machine (20) at a first voltage value, a phase control angle of the inverter (2) is changed such that a value thereof becomes larger as a rotation speed of the synchronous machine (20) becomes higher.