Open-Loop Phase Pre-Charge for Resistorless DC Bus Charging
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Solution Overview
Problem
Existing motor systems rely on resistor-based pre-charging circuits for rectifiers, which consume power, generate waste heat, and increase costs, limiting capacitance and efficiency.
Innovation Solution
The use of a Switching Mode Power Supply (SMPS) diode and a charge generator that pre-charges the SMPS to a regulation set point, detecting a specified phase angle of AC voltage to generate a charging voltage during positive intervals, eliminating the need for pre-charge resistors and enabling open-loop pre-charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistor-based pre-charging circuits are used for rectifiers, then the rectifier can be pre-charged, but power is consumed, waste heat is generated, and costs increase
Solution Approach 1:
The patent removes the resistor component from the pre-charging circuit entirely. Instead of using a resistor to limit in-rush current, the invention uses the inherent characteristics of the SMPS and controlled switching of the bridge rectifier to achieve pre-charging without dissipative elements, thereby eliminating power loss and heat generation associated with resistor-based pre-charging.
Solution Approach 2:
The SMPS unit performs its own pre-charging function using its internal components and the controlled rectifier bridge. The system uses itself to pre-charge the DC bus through controlled conduction of rectifier devices during specific AC voltage intervals, eliminating the need for external pre-charge resistors and their associated energy losses.
2Reliability
If pre-charge resistors are used, then the rectifier can be pre-charged, but capacitance is limited and efficiency decreases
Solution Approach 1:
By removing the pre-charge resistor from the circuit, the patent eliminates the limitation that resistors impose on capacitance selection. Without the resistor, the DC bus capacitor can be sized larger to store more energy, and the system efficiency is improved because no energy is dissipated in a resistive element during pre-charging.
Solution Approach 2:
The invention changes the pre-charging mechanism from a passive resistive voltage divider to an active controlled switching process. By controlling the conduction angle and timing of the rectifier bridge devices, the system can pre-charge the bus efficiently while allowing for larger capacitance values that would be impractical with resistor-based methods.
3Reliability
If resistor-based pre-charging is used, then pre-charging can be achieved, but component costs increase
Solution Approach 1:
The patent eliminates the pre-charge resistor component entirely from the bill of materials. By using the existing SMPS and rectifier bridge components in a controlled switching configuration, the system achieves pre-charging functionality without requiring additional expensive high-power resistor components, thereby reducing overall system cost.
Solution Approach 2:
The existing rectifier bridge and SMPS components are made to perform multiple functions: normal rectification and pre-charging. By controlling the conduction of the rectifier devices during specific AC voltage intervals, these components serve dual purposes, eliminating the need for separate pre-charge resistors and reducing component count and cost.
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 approach reduces component costs, increases capacitance, and improves efficiency by pre-charging the rectifier without resistors, thereby accelerating the motor system's operation and reducing power consumption.
Implementation Method 1
The SMPS charging diode pre-charges an SMPS to a regulation set point from at least one phase of an Alternating Current (AC) voltage
Implementation Method 2
the charge generator iteratively generates a charging voltage during positive voltage interval that charges a Direct Current (DC) bus capacitor to a target DC bus voltage
Data Source
AI summary
For open loop phase pre-charge, an apparatus includes a Switching Mode Power Supply (SMPS) charging diode and a charge generator. The SMPS charging diode pre-charges an SMPS to a regulation set point from at least one phase of an Alternating Current (AC) voltage. The charge generator is powered by the pre-charged SMPS. In response to detecting the regulation set point iteratively, the charge generator detects a specified phase angle of the AC voltage. In response to the specified phase angle, the charge generator iteratively generates a charging voltage during positive voltage interval that charges a Direct Current (DC) bus capacitor to a target DC bus voltage within a charging time interval. At least a portion of the charge generator comprises one or more of hardware and executable code, the executable code stored on one or more computer readable storage media.