Synchronous Machine Starting Device Induction Voltage Computation
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Solution Overview
Problem
Conventional synchronous-machine starting devices face challenges in accurately detecting the low voltage and position of the rotor at start-up, leading to instability in starting synchronous machines due to the difficulty in precise voltage detection and rotor position sensing.
Innovation Solution
A synchronous-machine starting device is designed with an electric power conversion unit, AC voltage and current detection units, a rotor position detection unit, and an electric power conversion control unit, which calculates and adjusts the induction voltage and rotational speed to stabilize the start-up process by using a selection unit to bypass the induction voltage operating unit during low voltage conditions and employing a PLL circuit to correct phase errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the synchronous machine is started with conventional voltage detection methods, then the structure is simple, but the voltage detection precision deteriorates at low voltage conditions
Solution Approach 1:
The patent introduces an induction voltage operating circuit as an intermediary computation system. Instead of directly detecting the low voltage at the armature terminal, the system computes the induction voltage based on measured current and estimated rotor position/speed. This intermediary calculation approach enables precise voltage detection at low voltage conditions without requiring direct high-precision voltage sensing hardware.
Solution Approach 2:
The patent replaces direct voltage measurement (electrical detection) with an indirect computation method based on electromagnetic induction principles. By substituting the mechanical/electrical voltage sensor with a computational model that calculates induction voltage from current and rotor state measurements, the system achieves higher precision without proportionally increasing hardware complexity.
2Reliability
If the mechanical distributor is used for rotor position detection, then the detection method is reliable, but the device is liable to be broken and influenced by noise
Solution Approach 1:
The patent replaces the mechanical distributor with an electrical/computational detection system. The rotor position is determined through computation based on induction voltage calculations and PLL (Phase-Locked Loop) processing, eliminating mechanical moving parts and associated wires. This substitution removes the mechanical failure modes and noise susceptibility inherent in contact-based mechanical distributors.
Solution Approach 2:
Instead of directly sensing rotor position through mechanical contact, the system creates a computational model that replicates the rotor position information through electrical measurements and mathematical processing. The PLL circuit generates a copied phase signal that corresponds to the actual rotor position, providing reliable detection without mechanical interaction.
3Ease of operation
If the voltage supplied to the armature is significantly lower than rated voltage, then the starting condition is achieved, but the voltage detection and rotor position sensing become inaccurate
Solution Approach 1:
The patent performs preliminary computation of induction voltage and rotor position estimation before actual starting operation. The system pre-calculates expected induction voltage based on applied current and estimated rotor state, then uses this preliminary information through PLL processing to establish accurate phase reference. This preliminary computational preparation enables precise detection even when actual armature voltage is very low.
Solution Approach 2:
The patent changes the detection parameter from direct armature voltage measurement to computed induction voltage. By transforming the detection approach from measuring the low-magnitude armature voltage directly to calculating induction voltage based on current and rotor state parameters, the system maintains detection precision across the full range of starting conditions including very low voltage scenarios.
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 configuration enables stable starting of synchronous machines by reducing detection errors and ensuring accurate rotor position sensing, even at low voltage conditions, thereby improving the reliability of the start-up process.
Implementation Method 1
an induction voltage operating unit calculating an induction voltage induced to the armature of the synchronous machine based on an estimated position signal representing the position of the rotor, an estimated rotational speed of the rotor, the AC voltage signal, and the AC current signal
Data Source
Figure 1
Figure 2~4
AI summary
A synchronous-machine starting device includes an induction voltage operating unit (61) calculating an induction voltage induced to an armature of a synchronous machine based on an estimated phase representing a position of a rotor, an estimated rotational speed of a rotor, an AC voltage signal, and an AC current signal, and outputting an induction voltage signal representing the calculated induction voltage, a selection unit (SEL) selecting and outputting one of the induction voltage signal received from the induction voltage operating unit (61) and the AC voltage signal received from the AC voltage detection unit, and a feedback operating unit (34) calculating an error of the estimated phase based on the induction voltage signal or the AC voltage signal received from the selection unit (SEL), calculating the estimated phase and estimated rotational speed based on the calculated phase error, outputting a speed signal representing the calculated estimated rotational speed to the induction voltage operating unit (61), and outputting a position signal representing the calculated estimated phase to the electric power conversion control unit (19) and the induction voltage operating unit (61).