Variable speed drive for a compressor module
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Solution Overview
Problem
Compact and mobile refrigerator systems face challenges in minimizing standby power consumption, reducing undesired inrush currents, and providing over-voltage protection while maintaining a constant common negative/neutral voltage reference point, especially when powered by DC voltage sources like batteries and photovoltaic systems.
Innovation Solution
A variable speed drive comprising a voltage filter and polarity protection unit, a DC power supply, an inverter unit, a controllable load dump, and a control unit that includes a microprocessor, which operates a MOSFET switch to manage power states and reduce standby losses, protect against over-voltage, and modulate to minimize inrush currents, ensuring a well-defined common negative/neutral voltage reference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the variable speed drive operates with continuous power connection to the DC voltage source, then the compressor module can be driven without interruption, but standby power consumption increases
Solution Approach 1:
The patent applies dynamics by making the power connection dynamic rather than static. The controllable switch in the load dump circuit allows the system to transition between connected and disconnected states, enabling the compressor to operate only when needed while minimizing standby power consumption during idle periods.
Solution Approach 2:
The system implements periodic action through the controllable switch that periodically connects and disconnects the power supply to the compressor module. This allows the system to operate in cycles of active compression and standby, reducing overall energy consumption while maintaining productivity when required.
2Device complexity
If the variable speed drive directly connects to the DC voltage source without protection circuits, then the device complexity is reduced, but over-voltage damage risk increases
Solution Approach 1:
The patent applies beforehand cushioning by incorporating protection circuits that anticipate and prepare for over-voltage conditions before they occur. The voltage filter and controllable switch are pre-configured to detect and respond to voltage spikes, cushioning the sensitive electronics from damage before the harmful effect can manifest.
Solution Approach 2:
The voltage filter and controllable switch act as intermediary elements between the DC voltage source and the compressor module. These intermediaries monitor and condition the power supply, blocking harmful over-voltage transients while allowing normal operation, thus protecting the system without requiring complete redesign of the power connection architecture.
3Speed
If the variable speed drive immediately connects full power to the compressor module upon startup, then the compressor can start quickly, but undesired inrush currents increase
Solution Approach 1:
The patent applies preliminary action by preparing the power connection in advance through the controllable switch and voltage filter. Before full power is applied to the compressor, the system pre-configures the power path with appropriate filtering and control, allowing for a controlled ramp-up that prevents inrush currents while still achieving quick startup.
Solution Approach 2:
The system implements parameter changes by dynamically adjusting the voltage and current parameters delivered to the compressor during startup. The controllable switch modulates the power delivery, changing the electrical parameters from a blocked state to a controlled conduction state, thereby limiting inrush current while maintaining startup speed.
4Device complexity
If the variable speed drive lacks a defined common negative/neutral voltage reference, then the circuit design is simplified, but voltage reference stability deteriorates
Solution Approach 1:
The patent applies equipotentiality by establishing a defined common negative/neutral voltage reference that creates an equipotential baseline for all voltage measurements and control operations in the system. This reference point ensures stable voltage relationships between all components, enabling reliable control of the controllable switch and inverter unit.
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 effectively minimizes standby power consumption, reduces inrush currents, provides over-voltage protection, and maintains a constant common negative/neutral voltage reference, enhancing the reliability and efficiency of compact and mobile refrigerator systems powered by DC voltage sources.
Implementation Method 1
The control unit comprises a microprocessor which operates a MOSFET switch to manage power states and reduce standby losses, protect against over-voltage, and modulate to minimize inrush currents
Implementation Method 2
a voltage filter circuit configured for low-pass filtering a voltage of an associated DC voltage source
Implementation Method 3
a controllable load dump inserted in series with the positive polarity connection between the voltage filter and voltage polarity protection unit and the DC power supply unit
Data Source
AI summary
A variable speed drive comprises a voltage filter and voltage polarity protection unit including 1) a voltage filter circuit configured for low-pass filtering a voltage of an associated DC voltage source, and 2) a voltage polarity protection circuit configured to prevent incorrect polarity parring between the variable speed drive and the associated DC voltage source; a DC power supply unit being operatively connected to the voltage filter and voltage polarity protection unit via at least a positive polarity connection; an inverter unit being operatively connected to the DC power supply unit, a controllable load dump inserted in series with the positive polarity connection between the voltage filter and voltage polarity protection unit and the DC power supply unit, and a control unit configured to control at least the DC power supply unit, the inverter unit and the controllable load dump.