BLDC Compressor Reverse Positioning to Prevent Condenser Pressure Drop
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Compressor stoppage in refrigeration appliances leads to pressure drops in the condenser due to the non-return valve failing to close reliably when the compressor is stationary, resulting in inefficiencies.
Innovation Solution
A method and apparatus that involves slowing down the BLDC motor, positioning the rotor in a second rotation direction with a predefined torque to ensure the non-return valve closes reliably, preventing pressure drops by carefully controlling the motor's shutdown and positioning using a sensorless BLDC motor with incremental activation and pulse width modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the compressor is stopped by simply slowing down the motor, then the stopping process is simple, but the non-return valve fails to close reliably causing pressure drops in the condenser
Solution Approach 1:
The controller performs a preliminary positioning action by rotating the motor in reverse direction before final stoppage. This preliminary reverse rotation moves the piston away from the upper dead center position, creating sufficient pressure difference to ensure the non-return valve closes reliably before the compressor comes to complete rest
Solution Approach 2:
Instead of simply decelerating the motor in the forward direction, the controller inverts the rotation direction temporarily by applying torque in the reverse direction. This reverse rotation actively positions the piston to favor non-return valve closure, then transitions back to forward rotation for normal operation
2Loss of energy
If the compressor stops with the piston near upper dead center, then the motor stops efficiently, but pressure drops occur in the condenser due to non-return valve leakage
Solution Approach 1:
Before the compressor enters the stationary phase, the controller executes a preliminary reverse positioning maneuver that actively prevents the harmful pressure drop condition. By positioning the piston away from upper dead center during the deceleration phase, the system proactively eliminates the root cause of non-return valve leakage and subsequent condenser pressure drops
Solution Approach 2:
The controller utilizes the motor's deceleration phase and residual kinetic energy to perform a beneficial reverse positioning action. What would normally be wasted energy during coasting to stop is converted into useful work that positions the piston favorably, ensuring non-return valve closure and preventing energy loss through condenser pressure drops
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
This approach ensures the non-return valve closes effectively, maintaining energy efficiency by preventing pressure drops in the condenser during compressor stationary phases.
Implementation Method 1
When current flows through the windings, they generate a magnetic field which applies a torque to the permanent magnet, thereby causing the rotor to move. Activating the various windings in the motor in an alternating manner causes a rotating magnetic field to be generated which therefore drives the rotor.
Implementation Method 2
The maximum pressure in the cylinder is reached when the piston is in the upper dead center position. The non-return valve prevents the refrigerant already conveyed into the line segment to the condenser from flowing back into the compressor.
Data Source
AI summary
A compressor of a refrigeration appliance includes a motor, in particular a BLDC motor, and a controller for stopping the motor. The controller is configured to slow down the motor rotating in a first rotating direction until it comes to a standstill and to subsequently position the rotor relative to the stator, in a second rotating direction with a predetermined torque. A method for stopping a compressor of a refrigeration appliance is also provided.