BLDC Compressor Rotor Positioning to Prevent Check Valve Pressure Loss
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Solution Overview
Problem
Compressor stopping in refrigeration appliances leads to pressure reduction in the condenser due to insufficient closure of the check valve, resulting in reduced energy efficiency, as the pressure difference is too small to overcome frictional forces when the piston stops near top dead center.
Innovation Solution
A method and device for stopping a compressor that involves braking the BLDC motor in one direction and positioning it in a second direction with a predetermined torque, ensuring the check valve closes securely, thereby preventing pressure reduction in the condenser. This is achieved by using a sensorless BLDC motor controller that steps the motor through a rotating magnetic field, selecting a torque smaller than the maximum to allow the rotor to stop before top dead center, ensuring the check valve closes effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the compressor is stopped without rotor positioning, then the stopping process is simple and quick, but the check valve does not close reliably causing pressure loss in the condenser
Solution Approach 1:
The control unit performs preliminary action by positioning the rotor in a specific angular position before the compressor stops. This preliminary positioning ensures that when the piston reaches top dead center, the pressure difference is sufficient to close the check valve reliably, preventing refrigerant leakage and maintaining condenser pressure.
Solution Approach 2:
The invention changes the parameter of rotor angular position during the stopping process. By controlling the rotor to stop at a specific angle rather than any random position, the system ensures optimal pressure differential across the check valve, transforming an unreliable closure into a reliable one through parameter optimization.
2Loss of energy
If the rotor is positioned to ensure check valve closure, then pressure loss is prevented, but the stopping process requires additional control steps
Solution Approach 1:
The control unit performs preliminary positioning of the rotor before the compressor stops. This preliminary action ensures that the rotor is in the optimal angular position when stopping, creating sufficient pressure difference to close the check valve and prevent energy loss through refrigerant leakage from the condenser.
Solution Approach 2:
The control unit uses feedback from motor current sensing to detect rotor position and adjust the stopping sequence accordingly. By monitoring the back-EMF or current characteristics, the system determines when the rotor has reached the desired angular position and coordinates the braking action to maintain optimal positioning during shutdown, preventing energy loss.
3Productivity
If the compressor piston stops near top dead center, then the compression cycle is complete, but the pressure difference is insufficient to close the check valve against friction
Solution Approach 1:
The invention changes the angular position parameter of the rotor during the stopping process. By controlling the rotor to stop at a specific angle where the piston is slightly before top dead center, the system maximizes the pressure difference across the check valve, ensuring reliable closure against friction forces while maintaining compression cycle efficiency.
4Loss of energy
If the check valve fails to close, then refrigerant flows back causing pressure reduction, but no additional components are needed
Solution Approach 1:
The control unit employs feedback mechanisms to monitor motor parameters during the stopping process and adjust the braking and positioning actions accordingly. This feedback control ensures the rotor reaches the optimal angular position for check valve closure, maintaining condenser pressure and preventing energy loss without requiring additional mechanical 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 ensures secure closure of the check valve during compressor standstill, preventing pressure reduction in the condenser and enhancing energy efficiency by maintaining optimal pressure levels, which is advantageous for refrigeration appliances.
Implementation Method 1
When current flows through the windings, they generate a magnetic field that exerts a torque on the permanent magnet, thus setting the rotor in motion. By alternately energizing the different windings in the motor, a rotating magnetic field is generated, which then drives the rotor.
Implementation Method 2
The maximum pressure in the cylinder is reached at the piston's top dead center. This check valve prevents refrigerant, already pumped into the condenser line, from flowing back into the compressor. During operation, the check valve allows refrigerant to be drawn in again during the next rotation of the rotor shaft.
Data Source
Figure 1
Figure 2A~3
AI summary
The invention relates to a compressor of a refrigeration device comprising a motor (100) and a control for stopping the motor, in particular a BLDC motor. Said control (160) is designed to slow down the rotating motor (100) until it comes to a standstill in a first rotating direction (206), subsequently to position the motor, with respect to the stator, in a second rotating direction (208, 209) having a predetermined torque.