Drive device, compressor, air conditioner, and drive method
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Solution Overview
Problem
During the operation of motors in air conditioners, a special operation state can occur where current flows only in two of three-phase coils, leading to demagnetization of permanent magnets, which existing technologies fail to adequately prevent.
Innovation Solution
The solution involves setting the overcurrent threshold for the delta connection to be less than √3 times the threshold for the Y connection, ensuring that demagnetization of permanent magnets is reduced even in special operation states by adjusting the connection state of the coils between Y and delta connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the overcurrent threshold for delta connection is set to √3 times the threshold for Y connection, then the motor can operate at higher current in delta connection, but demagnetization of permanent magnets occurs in special operation states
Solution Approach 1:
The patent changes the overcurrent threshold parameter based on the connection state. Specifically, when switching from Y connection to delta connection, the overcurrent threshold is set to a value less than √3 times the Y connection threshold (e.g., 0.95 to 1.05 times √3 times). This parameter adjustment prevents demagnetization in special operation states while maintaining adequate power output capability.
2Productivity
If the connection state of coils is switched between Y and delta, then motor efficiency is improved for different speed ranges, but complex control is required to manage switching and threshold adjustments
Solution Approach 1:
The patent implements dynamic switching between Y and delta connections based on motor operating conditions (speed, load). The control system dynamically adjusts the overcurrent threshold according to the active connection state, enabling efficient operation across different speed ranges while maintaining protection against demagnetization through automated state-dependent parameter adjustment.
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 effectively reduces demagnetization of permanent magnets in both Y and delta connections, enhancing the reliability and efficiency of motor operation while allowing for higher driving efficiency and reduced manufacturing costs by eliminating the need for dysprosium in rare earth magnets.
Implementation Method 1
a connection state of coils of a motor for driving a compressor is switched between a Y connection (also referred to as a star connection) and a delta connection (also referred to as a Δ connection)
Implementation Method 2
In order to suppress demagnetization of a permanent magnet of a motor, the motor is stopped when an output current of an inverter reaches a threshold (overcurrent protection level)
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A driving device includes an inverter to output a voltage to coils, a connection switching unit to switch a connection state of the coils between a Y connection and a delta connection, and a controller. The controller causes the inverter to stop outputting, when the connection state of the coils is the Y connection and a current value of the inverter reaches a first threshold A, or when the connection state of the coils is the delta connection and the current value of the inverter reaches a second threshold B. The first threshold A and the second threshold B satisfy B < √3 × A.