Compressor Stator Heating Control for Cold-Start Crankcase Protection
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Solution Overview
Problem
Compressor crankcases in heat pump systems face 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 compressor crankcase heating control system using a stator of an electric motor to generate heat, with a processor-controlled module that selectively applies a lower voltage for efficient heating based on ambient and compressor temperatures, and schedules heating to minimize energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heating element is used to heat the crankcase, then the lubricant temperature is improved, but energy consumption increases
Solution Approach 1:
The stator winding is designed to perform dual functions: motor operation during compression cycles and heating during idle periods. By applying voltage to the stator winding, the system generates heat through electrical resistance without requiring a separate heating element, thereby reducing overall energy consumption while maintaining effective crankcase heating
Solution Approach 2:
The system uses its own motor components (stator winding) to provide heating service during idle periods. The controller activates the stator winding as a heating element when the compressor is not running, allowing the motor itself to serve the dual purpose of compression and heating, eliminating the need for external heating devices
2Use of energy by moving object
If the compressor starts with low crankcase temperature, then energy consumption is reduced, but bearing wear increases due to insufficient lubrication
Solution Approach 1:
The controller activates the stator winding as a heating element during idle periods before the compressor is needed. This preliminary heating action ensures that the lubricant reaches appropriate temperature and viscosity levels before compression operations begin, preventing bearing wear and ensuring reliable startup conditions without excessive energy consumption during operation
3Temperature
If liquid refrigerant returns to the compressor during running cycle, then cooling effect is improved, but lubricant dilution occurs leading to decreased performance
Solution Approach 1:
The controller continuously monitors system conditions and adjusts the heating cycle accordingly. By using feedback from temperature sensors and operational status, the system optimizes the duration and intensity of stator heating during idle periods, ensuring adequate lubricant temperature maintenance without excessive energy consumption, thereby preventing lubricant dilution while maintaining cooling performance
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 system effectively prevents cold starting and liquid migration, improves lubricant viscosity, and reduces energy waste by optimizing heating according to environmental conditions, enhancing compressor performance and efficiency.
Implementation Method 1
A compressor crankcase heating control system uses a stator of an electric motor to generate heat
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A first switching device includes a first and second inputs connected to first and second power lines, respectively, the first and second power lines for receiving a first voltage. The first switching device selectively connects and disconnects the first and second inputs to and from first and second nodes, respectively. A second switching device includes a third input connected to the first node, includes a fourth input connected to a third power line, and includes a first output connected to a first end of a stator winding. A third switching device includes a fifth input connected to the second node and includes a sixth input connected to a fourth power line, the third and fourth power lines for receiving a second voltage that is less than the first voltage. The third switching device further includes a second output connected to a second end of the stator winding. A compressor crankcase heating control module controls the second and third switching devices to control compressor crankcase heating.