Variable Speed Drive Common Mode Filtering and Cooling
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Solution Overview
Problem
Variable speed drives (VSDs) with active converters in HVAC&R applications face issues such as premature bearing failures due to common mode voltages, incorrect power factor control, and inadequate ground fault protection, along with bulky and heavy power assembly designs and inefficiencies in cooling systems.
Innovation Solution
A circuit configuration for PWM VSDs includes a converter stage, a DC link, an inverter stage, and an input filter to manage common mode and differential mode interference, along with a phase angle control circuit and ground fault protection using reverse blocking IGBTs, and a plastic cooling system for improved efficiency and reduced size and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active converter technology is used to provide power factor correction and reduced input current harmonics, then power factor control is improved, but common mode voltage increases causing motor and compressor bearing fluting and premature bearing failures
Solution Approach 1:
A common mode choke is introduced as an intermediary component between the active converter and the motor/compressor. This choke specifically targets and attenuates common mode voltage while preserving the differential mode power factor correction function. The choke acts as a mediator that filters out the harmful common mode component without interfering with the beneficial active converter operation.
2Ease of manufacture
If conventional aluminum electrolytic capacitors are used in the DC link, then the VSD can be manufactured with standard components, but the power assembly becomes bulky and heavy with inherent wear-out mechanisms
Solution Approach 1:
The patent changes the fundamental parameters of the capacitor technology by transitioning from aluminum electrolytic capacitors to film capacitors. This parameter change eliminates the wear-out mechanism inherent in electrolytic capacitors, reduces weight by approximately 50%, and extends operational life while maintaining the necessary electrical performance for DC link operation.
3Temperature
If aluminum heatsinks are used in liquid cooling systems, then cooling efficiency is improved, but corrosion concerns arise when copper components are in intimate contact with the cooling fluid
Solution Approach 1:
The patent employs a composite material strategy by using plastic (polymer) heatsinks instead of traditional aluminum or copper. This material substitution eliminates the galvanic corrosion issue between dissimilar metals in the cooling fluid environment while maintaining effective thermal transfer capabilities. The plastic acts as both a structural and thermal component, combining electrical insulation with heat dissipation function.
4Device complexity
If air-cooled inductors are used in low voltage VSDs, then the design is less expensive and simpler, but the inductor losses become problematic as active converter size and cost grow
Solution Approach 1:
The patent transitions from air-cooling to liquid cooling for the inductors in active converter VSDs. This hydraulic cooling approach provides superior heat removal capability, enabling the inductors to handle the increased losses associated with active converter technology. The liquid cooling system efficiently dissipates heat through forced circulation, maintaining lower operating temperatures and reducing energy losses.
5Adaptability or versatility
If extended bypass means with multiple three-phase contactors are implemented, then emergency bypass operation is provided, but device complexity and cost increase significantly
Solution Approach 1:
The patent extracts and eliminates unnecessary bypass components by implementing a simplified bypass architecture. Instead of using multiple three-phase contactor sets, the design uses a single strategically placed contactor that achieves the same emergency bypass function. This extraction of redundant components reduces device complexity, lowers cost, and simplifies maintenance while preserving the essential bypass capability.
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
The solution reduces common mode and differential mode currents, enables efficient bypass operation, provides instant ground fault protection, and improves cooling efficiency, leading to reduced size, weight, and cost, while maintaining high performance and reliability.
Implementation Method 1
a converter stage (202) connected to an AC power source (102) providing the input AC voltage. The converter stage (202) is configured to convert the input AC voltage to a boosted DC voltage
Implementation Method 2
A DC link (204) is connected to the converter stage (202), the DC link (204) configured to filter and store the boosted DC voltage from the converter stage (202)
Implementation Method 3
An inverter stage (206) is connected to the DC link (204), the inverter stage (206) configured to convert the boosted DC voltage from the DC link (204) into the output AC power having the variable voltage and the variable frequency
Implementation Method 4
an input filter (10) connected to the VSD at the input to the converter stage (202) for reducing a common mode component and a differential mode component induced by conducted electromagnetic interference or radio frequency interference present at the AC power source (102)
Data Source
AI summary
Systems and methods for improved Variable Speed Drives are provided. One embodiment relates to apparatus for common mode and differential mode filtering for motor or compressor bearing protection when operating with Variable Speed Drives, including conducted EMI/RFI input power mains mitigation. Another embodiment relates to a method to extend the synchronous operation of an Active Converter to the AC mains voltage during complete line dropout. Another embodiment relates to an Active Converter-based Variable Speed Drive system with Improved Full Speed Efficiency. Another embodiment relates to a liquid- or refrigerant-cooled inductor. The liquid- or refrigerant-cooled inductor may be used in any application where liquid or refrigerant cooling is available and a reduction in size and weight of a magnetic component is desired.