Off-Grid Generator Dual Voltage via Series Parallel Switching
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Solution Overview
Problem
Off-grid generator sets face inefficiencies in fuel usage and high costs due to the need for fixed engine speeds and the expense of frequency converters to maintain constant output frequency and dual voltage levels, which are not effectively addressed by existing technologies.
Innovation Solution
An off-grid power generating apparatus with a single phase winding stator and symmetric phase windings rotor, utilizing a switch to connect coils in series or parallel for dual voltage output and an excitation control device to regulate engine speed and magnetic field for constant frequency, eliminating the need for costly converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If converters are used to modulate voltage levels and maintain constant frequency, then the output voltage and frequency stability are improved, but the cost increases significantly (converters account for 20-60% of overall cost)
Solution Approach 1:
The single phase winding is divided into multiple coil segments that can be independently connected in series or parallel configurations. This segmentation allows the generator to provide dual voltage levels (e.g., 120V and 240V) without requiring expensive voltage conversion equipment, directly resolving the contradiction between reliability and cost.
Solution Approach 2:
The switch dynamically reconfigures the coil connections between series and parallel states based on the required output voltage level. This dynamic adaptability enables the system to maintain stable output voltage at different levels without using converters, addressing both reliability and cost concerns.
2Reliability
If engine speed is fixed to maintain constant frequency output, then the frequency stability is improved, but the fuel efficiency deteriorates when electrical load is less than rated load
Solution Approach 1:
The excitation control device adjusts the excitation current to the rotor windings based on the electrical load, thereby changing the magnetic field strength and maintaining constant frequency output even when engine speed varies. This allows the engine to operate at variable speeds for fuel efficiency while maintaining frequency stability through parameter adjustment rather than fixed speed operation.
Solution Approach 2:
The excitation control device monitors the electrical load and adjusts the excitation current accordingly, creating a feedback mechanism that maintains constant frequency output. This feedback control enables the engine to optimize fuel efficiency by varying speed while the system automatically compensates to maintain stable frequency output.
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 solution significantly reduces costs by eliminating the need for converters while maintaining efficient fuel usage and providing stable dual voltage outputs suitable for various electrical loads, enhancing the efficiency and adaptability of off-grid power generation.
Implementation Method 1
the engine rotates the common shaft to drive the alternator that, in turn, generates electrical power
Implementation Method 2
an excitation control device to regulate engine speed and magnetic field for constant frequency
Data Source
AI summary
An off-grid power generating apparatus is provided. The apparatus includes an engine, an alternator and an excitation control device. The alternator includes a rotor, a switch and a stator. The switch is movable between a first position and a second position. An output portion of the stator has first and second segments each of which has at least one coil. The first and second segments are operatively and separately connected with the switch. The first and second segments are connected in series at the first position and in parallel at the second position to provide a high voltage and a low voltage respectively. The excitation control device controls the output voltage to make it have a predetermined frequency, and to regulate the engine speed in response to the load power of the engine.