Voltage doubling circuit for laundry treating appliance with high power variable frequency drive
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Solution Overview
Problem
Laundry treating appliances with high load capacity, such as commercial washing machines, require a higher voltage supply than typically available in 120 VAC systems, leading to insufficient operating power for variable frequency drives (VFDs), with existing solutions being either limited in current capacity or requiring large, expensive transformers.
Innovation Solution
A voltage doubling circuit that charges capacitor banks through a current-limiting surge suppressor, allowing for a bypass path to increase the voltage from 120 VAC to 240 VDC, enabling the operation of VFDs with higher power requirements, such as up to 340 VDC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a 120 VAC input variable frequency drive with an internal doubling circuit is used, then the voltage is doubled to 240 VAC output, but the current capacity is limited to about 4.2 amps which is insufficient for high power loads
Solution Approach 1:
The patent extracts the voltage doubling function from the VFD's internal circuitry and implements it as a separate external circuit. This external voltage doubling circuit includes capacitor banks, diodes, and switching elements that operate independently from the VFD, thereby removing the current capacity limitations of internal doubling circuits while maintaining the voltage doubling capability.
Solution Approach 2:
The patent segments the power conversion system into distinct functional modules: an external voltage doubling circuit with its own capacitor banks and switching elements, and the VFD with its motor control functions. This segmentation allows each module to be optimized independently, enabling the voltage doubling circuit to provide high current capacity while the VFD handles precise motor control.
2Power
If a large step-up voltage doubling transformer is used to change from 120 VAC input to 240 VAC output, then sufficient voltage and power are provided, but the transformer is very large, heavy, and expensive
Solution Approach 1:
The patent replaces the mechanical transformer system with an electronic voltage doubling circuit. Instead of using electromagnetic induction through a heavy iron-core transformer, the circuit uses solid-state components including capacitor banks, diodes, and switching elements to achieve voltage multiplication. This substitution eliminates the need for heavy magnetic cores and windings, dramatically reducing weight and size while providing equivalent or superior power capacity.
Solution Approach 2:
The patent changes the operating parameters of the voltage conversion process by using high-frequency switching of capacitor banks instead of low-frequency electromagnetic transformation. The circuit switches capacitors on and off at controlled frequencies to synthesize the doubled voltage, operating in a different regime from traditional transformers and enabling compact, lightweight design with high power delivery capability.
3Productivity
If a voltage doubling circuit with bypass path is used to charge capacitor banks, then high current capacity is achieved, but surge current protection is needed during initial charging
Solution Approach 1:
The patent implements preliminary surge protection by placing current-limiting resistors in series with the capacitor banks before the bypass switch is engaged. During the initial charging phase, these resistors limit inrush current to safe levels. Once the capacitors are charged and the bypass switch closes, the resistors are effectively bypassed, allowing full high-current operation without the current-limiting restriction.
Solution Approach 2:
The patent creates a dynamic charging system where the circuit configuration changes based on the charging state. The bypass switch transitions the circuit from a high-impedance charging mode (with current-limiting resistors active) to a low-impedance discharge mode (with resistors bypassed). This dynamic reconfiguration allows the system to safely manage surge currents during initialization while maximizing current delivery during operation.
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 solution effectively supplies sufficient power to VFDs, enabling the operation of laundry treating appliances with higher power demands, while maintaining efficiency and reducing the need for large transformers.
Implementation Method 1
charging a first capacitor bank and a second capacitor bank through a current-limiting surge suppressor
Implementation Method 2
the first capacitor bank is operable to be charged by a positive half wave of the AC power source, and the second capacitor bank is operable to be charged by a negative half wave of the AC power source
Data Source
AI summary
A circuit that increases input voltage to higher output voltage connected to a variable frequency drive in an appliance. Several switching arrangements, timing, and safety mechanisms are in place to assist. When the circuit experiences high draw, high voltage output values of circuit decrease over time, but different aspects of the circuit can be constructed so that the amount of time required at a higher voltage does not exceed the amount of time in which the high voltage output is provided.