Compressor Current Detection for Short Power Failure Restart Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Air conditioner compressors with single-phase induction motors face issues with reversing direction after a power outage, leading to potential damage due to incomplete rotating magnetic fields and uneven torque, especially during extremely short power failures where existing solutions fail to prevent reversal effectively.
Innovation Solution
An air conditioner control device with a current detection unit that monitors the starting current after power restoration and turns off the electromagnetic switch if the current exceeds a prescribed level for a certain time, preventing the compressor from reversing and ensuring stable restart by waiting for pressure equilibrium before restarting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power supply monitor is used to detect power outages and reset the control device, then the compressor can be stopped to prevent reversing during long power failures, but the compressor may still reverse during extremely short power failures (several 10 ms or less) because the reset signal is not output in time
Solution Approach 1:
The patent replaces the conventional power supply monitor (electrical system) with a current detector that directly monitors compressor current. This substitution enables detection of power failures through current interruption rather than voltage monitoring, significantly reducing response time to several 10 ms or less and preventing compressor reversal during extremely short power failures.
Solution Approach 2:
The control device is configured to proactively stop the compressor when current interruption is detected, before the compressor can reverse. This preliminary action prevents the harmful reversing operation from occurring in the first place, rather than attempting to correct it after detection with delayed response.
2Reliability
If the control device stops the compressor immediately when power is restored to prevent reversing, then compressor damage is prevented, but the compressor cannot restart even when pressure equilibrium is achieved, reducing operational efficiency
Solution Approach 1:
The patent implements dynamic control where the compressor stopping duration is not fixed but adapts based on system conditions. The control device stops the compressor for a predetermined time after power restoration, then monitors pressure differential between evaporator and compressor. When pressure equilibrium is detected, the compressor is allowed to restart. This dynamic approach balances protection needs with operational efficiency.
Solution Approach 2:
The control device uses feedback from pressure differential detection to determine when to allow compressor restart. By continuously monitoring the pressure difference between evaporator and compressor after power restoration, the system determines the optimal restart timing, ensuring both compressor protection and operational efficiency.
3Productivity
If the compressor is allowed to restart immediately after power restoration, then operational efficiency is maintained, but the compressor may reverse and suffer damage if pressure equilibrium has not been achieved
Solution Approach 1:
The control device implements a predetermined waiting period after power restoration before allowing compressor restart. This preliminary action ensures pressure equilibrium is achieved before restart, preventing compressor reversal and damage while minimizing delay to operational efficiency.
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
Effectively prevents compressor reversal and damage during both short and long power failures, ensuring stable operation by differentiating starting currents and controlling the compressor's restart based on pressure balance.
Implementation Method 1
a current detector 71, rectification and smoothing circuits 72, and a current comparator 73
Implementation Method 2
rectification and smoothing circuits 72
Implementation Method 3
rectification and smoothing circuits 72
Implementation Method 4
an electromagnetic switch 2 that switches between an on state in which current supply to the compressor 1 is on
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A compressor (1) that could be caused to operate in reverse as a result of a power failure is reliably prevented from running in reverse even when an extremely short power failure of less than several 10 ms occurs, and damage to the compressor (1) is thus prevented. An electromagnetic switch (2) turns the current supply to the compressor (1) on and off. A 4-way valve (3) switches between heating and cooling modes. A current detection unit (7) detects the compressor (1) current. The control unit (4) turns the electromagnetic switch (2) off if the output from the current detection unit (7) is greater than or equal to a predetermined value continuously for a prescribed time or longer. The control unit (4) also does not detect the current detection unit (7) output for a prescribed time after outputting an on signal to the electromagnetic switch (2) or outputting an on/off signal to the 4-way valve (3).