Controls and operation of variable frequency drives
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Solution Overview
Problem
In HVACR systems, undesired or un-commanded compressor rotation poses significant issues, leading to potential damage and increased wear due to limitations in existing approaches for mitigating such occurrences, particularly in systems driven by electric motors and variable frequency drives.
Innovation Solution
A system comprising a refrigerant circuit with a compressor, condenser, expander, and electric motor, where a controller analyzes system conditions to identify risks of un-commanded rotation and controls the power supply to oppose rotation, using methods such as short circuit conditions or DC current to resist motor rotation, thereby preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing approaches are used to mitigate un-commanded compressor rotation, then some level of protection is provided, but the system suffers from limitations and disadvantages that fail to adequately prevent damage and wear
Solution Approach 1:
The controller proactively applies counter-torque to the motor before un-commanded compressor rotation can occur. By monitoring system conditions and detecting potential rotation risks, the controller preemptively activates the motor in a controlled manner to counteract any unwanted rotational forces, thereby preventing damage before it happens rather than reacting after the fact.
Solution Approach 2:
The system performs preliminary analysis of system conditions to identify risks of un-commanded rotation before they manifest. The controller continuously evaluates parameters such as pressure differentials and motor state, and when risk is detected, it activates the motor in advance to prevent the harmful rotation from occurring, ensuring the compressor is protected before damage can ensue.
2Measurement precision
If the controller continuously monitors system conditions to identify rotation risks, then protection accuracy is improved, but system complexity and computational requirements increase
Solution Approach 1:
The controller leverages existing sensors and system components already present in the HVACR system, making them serve the additional function of detecting rotation risks. By utilizing existing pressure sensors, motor controllers, and system state information for dual purposes (original function plus rotation risk detection), the system achieves accurate monitoring without adding significant complexity or requiring dedicated specialized components.
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 effectively prevents undesired compressor rotation, reducing the risk of damage and wear by accurately identifying and mitigating un-commanded rotation conditions, thus enhancing the reliability and longevity of HVACR system components.
Implementation Method 1
the controller being configured to control the power supply to provide a short circuit condition effective to provide an electrical resistance to current generated by rotation of the motor
Implementation Method 2
the controller being configured to control the power supply to provide a DC current to the motor effective to urge the motor to a predetermined alignment and resist rotation of the motor
Data Source
AI summary
A system includes a refrigerant circuit including a compressor, a condenser, an expander, an electric motor configured to drive the compressor, and a controller configured to control a motor drive to drive the electric motor. The controller is configured to first evaluate whether the compressor is idle based upon a control state of the controller being configured not to operate the motor drive to drive the motor, second, in response to an affirmative evaluation that the compressor is idle, evaluate a risk of undesired or un-commanded compressor rotation based upon a combination of two or more system conditions, each of the two or more system conditions indicating the risk of undesired or un-commanded compressor rotation, and third, in response to an affirmative evaluation of the risk of undesired or un-commanded compressor rotation, control the motor drive to oppose rotation of the compressor.