Field Winding Synchronous Machine Surge Voltage Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional field winding type synchronous machines face challenges in reducing starting current and efficiently disconnecting the discharge resistor during synchronized operation, leading to potential reconnection and heat generation issues due to surge voltages and lack of dedicated control circuits for thyristors.
Innovation Solution
The implementation of a field winding type synchronous machine with a rectification circuit connected to a DC line, including a field winding in parallel with a switchgear and a capacitor between the discharge resistor and the power source element, to minimize the possibility of discharge resistor reconnection and heat generation by using a capacitor as a low-pass filter to prevent thyristor activation by surge voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a discharge resistor is connected in parallel to the field winding to reduce starting current, then starting current is reduced, but the discharge resistor causes loss during stationary operation and must be disconnected
Solution Approach 1:
The discharge resistor connection state is made dynamic rather than static. During starting operation, the discharge resistor is connected to reduce starting current. During stationary operation, it is disconnected to eliminate energy loss. This dynamic switching resolves the contradiction between needing the resistor for starting and needing to eliminate it for efficient operation.
2Stability of the object's composition
If a smoothing capacitor is disposed in parallel to the rectification circuit to smooth DC voltage, then DC ripple is reduced, but the capacitor cannot correspond to high frequency surge voltages
Solution Approach 1:
The voltage filtering function is segmented into two different capacitors with different characteristics. The smoothing capacitor handles low-frequency DC ripple, while a separate surge capacitor handles high-frequency surge voltages. This segmentation allows each capacitor to be optimized for its specific frequency range, resolving the contradiction between ripple smoothing and surge protection.
3Ease of operation
If a thyristor is used to switch the field winding connection, then switching from start-up to synchronized operation is enabled, but the thyristor remains continuously conducting and generates heat
Solution Approach 1:
The thyristor switching is made periodic rather than continuous. The thyristor is turned on during starting operation to enable field winding connection, then turned off during synchronized operation to stop heat generation. This periodic on-off action maintains the switching capability while eliminating continuous heat generation.
4Ease of operation
If surge voltage is applied to a zener diode to control thyristor gating, then thyristor can be turned on, but the discharge resistor may be reconnected after synchronized operation
Solution Approach 1:
A capacitor is introduced as an intermediary element between the surge voltage source and the zener diode. This capacitor filters the surge voltage before it reaches the zener diode, preventing false thyristor triggering. By mediating the interaction between surge voltage and control circuit, the discharge resistor remains reliably disconnected during synchronized operation while still allowing proper thyristor control when needed.
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 reduces the likelihood of discharge resistor reconnection after synchronized operation and miniaturizes the circuit, effectively managing surge voltages and maintaining efficient operation by preventing thyristor activation, thus enhancing the overall efficiency and reliability of the synchronous machine.
Implementation Method 1
a capacitor being provided between the discharge resistor and the input side of an electric power source element for gating the first switchgear
Implementation Method 2
using a capacitor as a low-pass filter to prevent thyristor activation by surge voltages
Implementation Method 3
a rectification circuit that rectifies an output from the exciter and provides the output to the DC line
Implementation Method 4
an exciter that passes a current through a field winding of the rotor
Data Source
AI summary
A field winding type synchronous machine connects to a DC line and includes a rotor; a stator; an exciter that passes a current through a field winding of the rotor; and a rectification circuit that rectifies an output from the exciter and provides the output to the DC line. The synchronous machine includes the field winding being connected in parallel to a first circuit in which a parallel circuit including a rectifier element and a first switchgear is connected in series to a discharge resistor, a second switchgear being connected in series to the DC line that connects the first circuit to the rectification circuit, and a capacitor being provided between the discharge resistor and the input side of an electric power source element for gating the first switchgear.