Thyristor Starter Control for High-Speed Commutation Margin
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In thyristor starters for synchronous machines, the commutation of thyristors fails at high rotation speeds due to a shorter commutation margin time, which is insufficient to ensure reliable operation.
Innovation Solution
A thyristor starter system that includes a converter, DC reactor, inverter, controller, and voltage regulator, where the controller adjusts the phase control angle and field current to maintain a constant DC voltage and increase the induced voltage with rotation speed, thereby extending the commutation margin time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotation speed of the synchronous machine is increased, then the productivity is improved, but the commutation margin time becomes shorter causing commutation failure
Solution Approach 1:
The invention changes the parameter of induced voltage dynamically with rotation speed. Specifically, the induced voltage is increased as rotation speed increases, which compensates for the reduced commutation margin time and maintains sufficient commutation reliability at high speeds.
Solution Approach 2:
The invention makes the system dynamic by adjusting the induced voltage according to the rotation speed. The voltage regulator dynamically controls the field current to increase induced voltage when rotation speed exceeds reference speed, adapting the system to maintain commutation reliability across varying operating conditions.
2Speed
If the phase control angle increases linearly with rotation speed, then the AC power frequency matches the machine speed, but the commutation margin time becomes insufficient at high speeds
Solution Approach 1:
The invention changes the parameter of induced voltage to compensate for the linear phase control angle increase. By increasing induced voltage with rotation speed, the system maintains adequate commutation margin time even when phase control angle increases linearly to keep AC power synchronized with machine rotation.
3Ease of operation
If the induced voltage is kept constant, then the system is simple to control, but the commutation margin time becomes insufficient at high rotation speeds
Solution Approach 1:
The invention transitions from a static constant voltage control to a dynamic voltage control system. The voltage regulator dynamically adjusts induced voltage based on rotation speed, maintaining commutation reliability at high speeds while keeping the control logic relatively simple through automated feedback control.
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
Ensures reliable commutation of thyristors at high rotation speeds by maintaining a sufficient commutation margin time, preventing failures and ensuring stable operation.
Implementation Method 1
a converter that converts AC power into DC power
Implementation Method 2
a DC reactor that smooths the DC power
Implementation Method 3
an inverter that converts the DC power provided from the converter through the DC reactor into AC power having a variable frequency
Implementation Method 4
an induced voltage of the synchronous machine
Data Source
Figure 1
Figure 2(A)~2(D)
Figure 3
AI summary
In a thyristor starter, an inverter converts DC power provided from a converter through a DC reactor into AC power having a variable frequency, and supplies the AC power to a synchronous machine. A controller controls the inverter based on a phase control angle. A voltage regulator regulates an induced voltage of the synchronous machine by supplying a field current to the synchronous machine,. When a rotation speed of the synchronous machine exceeds a reference rotation speed during acceleration of the synchronous machine, the voltage regulator controls the field current such that the induced voltage increases with an increase in the rotation speed of the synchronous machine. The controller decreases a rate of increase in the phase control angle relative to the rotation speed of the synchronous machine, as compared with when the rotation speed of the synchronous machine is less than the reference rotation speed.