DC Link Cooling System for Electric Drive Retarding Energy Dissipation
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Solution Overview
Problem
Existing electric drive systems face inefficiencies and high costs due to the use of active cooling systems, such as fans or blowers, which dissipate electrical retarding energy as heat, reducing overall efficiency and depleting useful electrical power.
Innovation Solution
A cooling system for electric drive machines that employs a DC link with automatic switches and a chopper circuit to manage energy dissipation through resistor grids, using an electronic controller to adjust switch signals and duty cycles to optimize energy dissipation and minimize overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If forced convection cooling systems (fans or blowers) are used to cool impedance devices, then the temperature of the impedance devices is reduced, but the overall efficiency of the machine is reduced and useful electrical power is depleted
Solution Approach 1:
The patent converts the harmful thermal energy generated during retarding into useful electrical energy by using the heat from impedance devices to generate electricity through thermoelectric generators, which then powers the cooling fans and reduces the load on the electrical power system
Solution Approach 2:
The patent merges the cooling function with the retarding energy dissipation function by integrating thermoelectric generators directly onto the impedance devices, creating a combined system where heat from retarding is immediately converted to power the cooling system
2Temperature
If active cooling systems with fans or blowers are implemented, then the temperature of impedance devices is controlled, but the system complexity and cost increase due to transformers, high voltage isolators, and voltage regulation equipment
Solution Approach 1:
The patent extracts the voltage regulation function from the complex transformer and isolator system by using solid-state power electronics with pulse-width modulation to control motor speed, eliminating bulky magnetic components and high-voltage isolation equipment
Solution Approach 2:
The patent replaces the mechanical transformer and isolator system with electronic control circuitry that uses pulse-width modulation and solid-state switching to achieve the same voltage regulation and motor control functions with greater precision and less complexity
3Temperature
If DC motors with voltage regulation equipment are used to drive cooling fans, then the cooling function is achieved, but the drive system efficiency is reduced due to power loss in transformers and voltage regulation devices
Solution Approach 1:
The patent implements a feedback control system that monitors the actual temperature of impedance devices and the power available from the retarding system, dynamically adjusting the cooling fan speed to match actual cooling requirements and maximize the use of otherwise wasted retarding energy
Solution Approach 2:
The patent uses dynamic pulse-width modulation control that continuously adjusts the motor operating parameters based on real-time conditions, allowing the system to operate at optimal efficiency across varying loads and temperatures rather than at fixed inefficient operating points
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 manages energy dissipation, reduces temperature, and enhances the efficiency of electric drive systems by minimizing energy loss and maintaining electrical power availability.
Implementation Method 1
A typical electrical retarding system includes a series of resistors or other impedance devices, through which thermal energy is dissipated when electrical current passes therethrough
Implementation Method 2
Forced convection by use of a fan or blower provides one form of active cooling for impedance devices used in electric retarding systems
Data Source
AI summary
A cooling system for a retarding system of an electric drive machine (100) includes a direct current (DC) link having first and second rails. A first resistor grid (214) is selectively placed in circuit between the rails by an automatic switch (216) in response to a switch (216) signal. A second resistor grid (218) is selectively placed in circuit between the rails by a chopper circuit (220) connected in series with the second resistor grid (218). The chopper modulates a current passing therethrough based on a duty cycle. A motor (336) is in parallel electrical connection across a portion of the first resistor grid (214) and operates in response to a motor (336) signal. An electronic controller (400) calculates a net energy during operation and adjusts the switch (216) signal, the duty cycle, and the motor (336) signal to close the automatic electrical switch (216) and operate the motor (336) when the net energy exceeds a threshold value.