Autotransformer Neutral Voltage Cancellation for Remote Power Lines
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Solution Overview
Problem
Long electric cables used for remote active devices, such as outdoor communication devices, experience significant power line voltage drops, leading to too-low phase voltage and too-high neutral line voltage, which cannot be corrected by existing solutions without risking safety violations, especially due to untreated neutral line parasite voltage.
Innovation Solution
A Phase and Neutral Voltage Adjusting (PNVA) device utilizing an autotransformer with single-port-to-multi-port controllable selector switches and a controller to adjust both phase and neutral output voltages, ensuring the voltage between the neutral terminal and ground is close to zero and the phase voltage is maintained at a nominal level, thereby canceling parasite voltage on the neutral line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the supply voltage level is increased to compensate for voltage drops in long cables, then the phase voltage at the remote end can be maintained at nominal level, but the neutral line voltage exceeds safety limits (60V/90VAC for outdoor communication network)
Solution Approach 1:
The patent segments the voltage adjustment function into two independent parts: phase voltage adjustment and neutral line voltage adjustment. The phase voltage is adjusted through the autotransformer winding connections, while the neutral line voltage is adjusted through the selector switch that connects different neutral points. This segmentation allows each parameter to be controlled independently, resolving the contradiction between maintaining phase voltage stability and keeping neutral line voltage within safety limits.
Solution Approach 2:
The patent employs dynamic adjustment mechanisms where the autotransformer and selector switch can adaptively change their configuration based on the detected voltage conditions. The controller continuously monitors phase and neutral voltages and dynamically adjusts the transformer taps and selector switch positions to maintain both phase voltage at nominal level and neutral voltage within safety limits, making the system responsive to changing load conditions.
2Reliability
If known devices adjust the phase voltage at the output, then the voltage between phase terminal and neutral terminal can be restored to nominal level, but the parasite voltage on the neutral line is left untreated causing safety risks
Solution Approach 1:
The patent extracts the neutral line voltage adjustment function from the conventional phase voltage adjustment mechanism. By introducing a separate selector switch that independently controls the neutral line connection, the system can take out and separately manage the parasite voltage issue. This allows the phase voltage to be restored to nominal level through the autotransformer while the neutral line voltage is simultaneously adjusted to eliminate parasite voltage, preventing safety risks.
3Length of stationary object
If the cable length is extended to reach remote devices, then coverage area is increased, but voltage drops exceed allowed thresholds
Solution Approach 1:
The patent introduces an autotransformer as an intermediary device at the remote end of the long cable. This intermediary compensates for the voltage drops accumulated over the extended cable length by providing voltage transformation and adjustment. The autotransformer, combined with the selector switch and controller, acts as a local voltage regulation system that enables the cable to be extended to reach remote devices while maintaining reliable voltage delivery through active compensation.
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 PNVA device effectively addresses voltage drops and neutral line parasite voltage, ensuring the active device receives power at a nominal voltage level, maintaining a safe voltage difference between the neutral and ground terminals, thus preventing safety risks and adhering to regulatory voltage limits.
Implementation Method 1
an autotransformer which comprises a plurality of taps each connected to a separate winding of the autotransformer
Data Source
AI summary
A device for cancellation of parasitic voltage on the neutral line and for adjusting phase-to-neutral voltage at the remote end of a long power line comprises an autotransformer and at least two single-port-to-multi-port controllable selectors and a controller. The controller is adapted to enable educated selection of taps of the autotransformer by the controllable single-port-to-multi-port controllable selectors, for setting the phase-to-neutral output voltage to nominal voltage and for canceling the parasitic neutral-to-ground voltage.