Capacity control technique with motor temperature override
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Solution Overview
Problem
In vapor compression systems like chillers, existing control systems often face conflicts between capacity control, surge/stall control, and motor temperature control, leading to potential compressor damage and shutdowns due to uncontrolled motor heat generation and operational instabilities.
Innovation Solution
A chiller system with a motor cooling valve that is electronically adjustable to regulate refrigerant flow for motor cooling, combined with a capacity control system that adjusts based on motor temperature thresholds to prevent overheating and maintain system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If capacity control increases compressor loading to meet cooling demand, then system productivity improves, but motor temperature rises beyond acceptable limits causing shutdown
Solution Approach 1:
The patent introduces motor temperature as an intermediary parameter that mediates between capacity control and surge/stall control. When motor temperature exceeds the second threshold, it overrides capacity control adjustments, forcing a reduction in compressor loading to prevent shutdown while maintaining surge/stall protection
Solution Approach 2:
The patent implements dynamic adjustment of capacity control based on real-time motor temperature monitoring. The capacity control system dynamically modifies compressor loading by adjusting inlet guide vane position or impeller outlet guide vane position in response to motor temperature thresholds, creating a adaptive control strategy that balances productivity with thermal protection
2Stability of the object's composition
If surge control opens hot gas bypass valve to increase inlet flow, then compressor stability improves, but motor temperature increases due to reduced effective capacity
Solution Approach 1:
The patent implements feedback control by monitoring motor temperature and using this information to modulate the hot gas bypass valve position. When motor temperature rises, the system feedback-adjusts the bypass valve to reduce recirculation flow, thereby reducing motor heating while maintaining minimum stable operating conditions
3Productivity
If capacity control adjusts inlet guide vane position to control refrigerant flow, then system capacity is regulated, but motor temperature may exceed limits
Solution Approach 1:
The patent implements dynamic adjustment of capacity control based on real-time motor temperature monitoring. The capacity control system dynamically modifies compressor loading by adjusting inlet guide vane position or impeller outlet guide vane position in response to motor temperature thresholds, creating a adaptive control strategy that balances productivity with thermal protection
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 manages motor temperature to prevent shutdowns and maintain system capacity, reducing the risk of compressor damage and ensuring stable operation by integrating motor cooling with capacity control.
Implementation Method 1
The motor is fluidly coupled to the condenser to allow the motor to receive refrigerant from the condenser to cool the motor
Data Source
AI summary
A control system includes processing and memory circuitry, the memory circuitry storing a temperature-based capacity control scheme for a chiller system and the processing circuitry being configured to perform the temperature-based capacity control scheme. The motor temperature-based capacity control scheme is performed as a function of a monitored temperature in a motor configured to drive a compressor of the chiller system, a first temperature threshold corresponding to the monitored temperature, and a second temperature threshold corresponding to the monitored temperature higher than the first temperature threshold.