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 excessively large and expensive.
Innovation Solution
A washing machine design incorporating a voltage doubling circuit with a power input, capacitor bank, and current-limiting surge suppressor to receive a 120 VAC supply and output up to 240 VDC to a VFD, enabling operation with higher voltage than the input power source during high power draw phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a 120 VAC input variable frequency drive with an internal doubling circuit is used, then the voltage is doubled to achieve higher output voltage, but the current capacity is limited to about 4.2 amps which is insufficient for high power loads
Solution Approach 1:
The voltage doubling function is separated from the VFD and implemented as a dedicated external circuit board assembly. This segmentation allows the doubling circuit to be optimized for voltage multiplication while the VFD is optimized for current delivery, resolving the contradiction between achieving high voltage and maintaining high current capacity.
Solution Approach 2:
A capacitor bank serves as an energy storage intermediary between the 120 VAC input and the VFD. The capacitors accumulate energy during low-demand periods and discharge during high-power phases, enabling the system to deliver both high voltage and high current without direct transformation loss.
2Temperature
If a step-up voltage doubling transformer is used to change from 120 VAC input to 240 VAC output, then the voltage transformation is achieved, but the transformer becomes very large, heavy, and expensive
Solution Approach 1:
The mechanical transformer system is replaced with an electronic voltage doubling circuit using diodes, capacitors, and control logic. This substitution eliminates the need for heavy magnetic cores and windings, achieving voltage multiplication with minimal weight and cost while maintaining high efficiency.
Solution Approach 2:
The circuit changes the operating parameters by using switched capacitor networks instead of electromagnetic induction. By controlling the charging and discharging of capacitors through semiconductor switches, the system achieves voltage multiplication without the physical constraints of transformer design.
3Power
If a voltage doubling circuit is used to supply higher voltage to the VFD, then the power capacity is increased, but the circuit complexity increases with additional components
Solution Approach 1:
The voltage doubling circuit is merged with the existing VFD control board assembly, sharing common components such as the microcontroller, power switches, and heat sinks. This integration approach increases power capacity while minimizing the increase in overall circuit complexity by reusing existing infrastructure.
Solution Approach 2:
The control board assembly is designed to perform multiple functions: it controls the VFD operation, manages the voltage doubling circuit, and coordinates capacitor charging/discharging cycles. This multi-functionality reduces the need for separate dedicated circuits, thereby limiting the growth of system complexity.
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 configuration allows for efficient operation of the washing machine by supplying up to 340 VDC to the VFD, overcoming the limitations of existing solutions and supporting higher power demands during acceleration and extraction phases.
Implementation Method 1
at least one capacitor bank connected with the power input where the at least one capacitor bank is at least partially discharged during high power draw portions of the cycle of operation
Implementation Method 2
a current-limiting surge suppressor positioned between the power input and the at least one capacitor bank
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.