Capacitorless Single-Phase to Two-Phase Power Conversion
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Solution Overview
Problem
Conventional single-phase motors without capacitors have limited applications due to their inability to generate a rotating magnetic field for startup, leading to torque pulsation and restricted rotor direction determination, while capacitor motors have a limited lifespan.
Innovation Solution
A power conversion method that converts single-phase AC voltage into two-phase AC voltage without using capacitors, utilizing bidirectional switches and control signals to generate voltages with specific amplitudes and phase differences, suitable for driving two-phase induction motors with variable RPM and torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitor motor is used to generate rotating magnetic field for startup, then the motor can achieve reliable startup and rotation control, but the lifespan is limited by the capacitor's lifespan
Solution Approach 1:
The invention extracts and eliminates the capacitor component from the motor system by using a power conversion apparatus that generates two-phase AC voltage directly from single-phase AC power supply without requiring capacitors for phase shift, thereby removing the reliability limitation imposed by capacitor lifespan
Solution Approach 2:
The power conversion apparatus acts as an intermediary device that converts single-phase AC power into two-phase AC power with appropriate phase difference, replacing the traditional capacitor-based phase shift method and enabling capacitorless motor operation
2Duration of action of stationary object
If a single-phase motor without capacitor is used, then the motor structure is simplified and lifespan is extended, but the motor cannot generate rotating magnetic field for startup and causes torque pulsation
Solution Approach 1:
The invention changes the electrical parameters of the power supply by converting single-phase AC voltage into two-phase AC voltage with specific amplitude ratios and phase differences, enabling the motor to generate rotating magnetic field and eliminate torque pulsation while maintaining capacitorless operation
Solution Approach 2:
The power conversion apparatus provides multiple functions including voltage conversion, phase generation, and startup assistance, enabling a simple capacitorless motor structure to achieve reliable startup and stable operation previously only available in capacitor motors
3Reliability
If a matrix converter is used to convert single-phase AC to three-phase AC, then the motor driving current becomes stable and efficient, but the device complexity increases
Solution Approach 1:
The invention segments the power conversion function into dedicated components for two-phase voltage generation, simplifying the overall system architecture compared to three-phase conversion while maintaining stable motor driving current through controlled switching of bidirectional switches
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 method enables efficient generation of two-phase AC voltage from single-phase AC, providing a long-life, reliable motor system for home appliances with variable RPM and torque without the need for starting capacitors.
Implementation Method 1
four first bidirectional switches each corresponding to a different combination of one of the paired input terminals and one of the paired first output terminals to switch connection and disconnection between the corresponding input terminal and first output terminal according to a corresponding one of first control signals
Data Source
AI summary
An efficient and reliable power conversion method for converting an input voltage which is a single-phase AC voltage into output voltages forming a two-phase AC voltage includes: receiving an input voltage; designating, as a first target voltage representing consecutive target values of a first-phase output voltage and a second target voltage representing consecutive target values of a second-phase output voltage, AC voltages forming a two-phase AC voltage and having (i) an amplitude 1/â2 times smaller than an amplitude of the input voltage, and (ii) phase differences of +45 degrees and â45 degrees relative to the input voltage; and designating a frequency other than a frequency twice a frequency of the input voltage, as a frequency of the first target voltage and the second target voltage.