Compressor crankcase heating control systems and methods
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Solution Overview
Problem
Compressor crankcases experience issues with cold starting and liquid flood-back due to low lubricant viscosity, leading to bearing wear and decreased performance, and existing heating methods are inefficient and wasteful.
Innovation Solution
A method and system for controlling compressor crankcase heating using the stator of an electric motor, where the stator generates heat when supplied with current to warm the lubricants and evaporate refrigerant, with the heating being selectively turned on or off based on ambient and compressor temperatures, and the use of a lower voltage for efficient heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a compressor crankcase heater is continuously operated to maintain lubricant viscosity, then bearing protection is improved, but energy consumption increases
Solution Approach 1:
The crankcase heater is operated periodically rather than continuously. The control system monitors compressor runtime and activates the heater during specific periods when the compressor is off and the crankcase temperature drops below a threshold, thereby maintaining bearing protection while reducing overall energy consumption
Solution Approach 2:
The system uses temperature sensors and runtime tracking to provide feedback about crankcase conditions. Based on this feedback, the control system intelligently decides when heater activation is necessary, optimizing the balance between bearing protection and energy consumption
2Temperature
If high voltage is applied to the stator for rapid heating, then crankcase temperature recovery is improved, but energy waste increases
Solution Approach 1:
The heating voltage is made dynamic rather than fixed. The system adjusts the voltage level applied to the stator based on real-time conditions such as current crankcase temperature, ambient temperature, and compressor runtime, enabling efficient temperature recovery without excessive energy waste
Solution Approach 2:
The system changes the electrical parameter (voltage) applied to the stator based on thermal conditions. By monitoring temperature and adjusting voltage levels accordingly, the system achieves effective crankcase heating while minimizing energy consumption
3Productivity
If the heater is activated based on multiple conditions (ambient temperature, compressor runtime, crankcase temperature), then heating efficiency is improved, but control system complexity increases
Solution Approach 1:
The control system divides the heating decision-making into separate functional modules: ambient temperature sensing, runtime tracking, crankcase temperature monitoring, and heater control logic. This segmentation allows each function to be independently optimized while maintaining overall system efficiency
Solution Approach 2:
The control system integrates multiple functions into a single unified controller that handles temperature monitoring, runtime tracking, and heater activation decisions. This multi-functionality approach improves heating efficiency by coordinating all parameters while managing complexity through integration
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
Improves lubricant viscosity and prevents damage by selectively heating the crankcase, reducing energy consumption and increasing efficiency by only heating when necessary.
Implementation Method 1
the stator generates heat when supplied with current to warm the lubricants and evaporate refrigerant
Data Source
AI summary
A compressor crankcase heating control method for a heat pump system includes selectively actuating a first switching device to connect and disconnect first and second power lines to and from second and third switching devices, respectively, the first and second power lines receive a first voltage. The compressor crankcase heating control method further includes, when the first and second power lines are disconnected from the second and third switching devices via the first switching device, actuating the second and third switching devices thereby connecting third and fourth power lines to ends, respectively, of at least one winding of a stator of an electric motor of a compressor. The at least one winding of the stator of the electric motor heats the crankcase of the compressor. The third and fourth power lines receive a second voltage that is less than the first voltage.