Motor control device
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Solution Overview
Problem
Existing motor control devices for heat pump type refrigeration apparatuses and water heaters face challenges in minimizing the influence of noise on rotor position estimation during the operation of one motor on the control of another, particularly when using rotor position sensorless control for brushless DC motors, leading to unstable control and potential failures.
Innovation Solution
A motor control device that includes a power supply unit and two inverters, where the control unit determines whether a compressor motor is performing a large current operation and avoids starting the fan motor during such operations to prevent noise interference, allowing for stable rotor position estimation and preventing unnecessary shutdowns by retrying inverter operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If rotor position sensorless control is used for brushless DC motors, then the structure is simplified and cost is reduced, but control stability deteriorates when noise is added to detection values during large current operations
Solution Approach 1:
The control unit prohibits startup of the fan motor when large current operation of the compressor motor is detected, preventing noise interference with rotor position estimation before it can occur. This preliminary preventive action eliminates the contradiction by avoiding the problematic condition entirely.
2Productivity
If the fan motor is started during compressor motor operation, then system productivity is improved, but measurement precision of rotor position deteriorates due to noise interference
Solution Approach 1:
The control unit detects large current operation of the compressor motor and prohibitively prevents fan motor startup during this period, eliminating noise interference with rotor position detection before it can affect measurement precision.
3Reliability
If abnormality detection is performed continuously, then system reliability is improved, but false abnormality detections increase during large current operations due to noise
Solution Approach 1:
By prohibiting fan motor startup during compressor motor's large current operation, the invention prevents noise generation at the source, thereby eliminating false abnormality detections while maintaining continuous monitoring capability for genuine faults.
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 effectively prevents startup abnormalities and unwanted shutdowns of the fan motor by synchronizing the operation with the compressor motor's large current phases, ensuring stable motor control and normal operation without false abnormality detections.
Implementation Method 1
an inverter that converts an output from a power supply unit to alternating current and supplies the output to a brushless DC motor
Data Source
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AI summary
An object of the present invention is to provide a motor control device, which drives at least one of two motors using rotor position sensorless control and controls one motor using the rotor position sensorless control without a failure due to control of an operation of the other motor. In the motor control device (10), a startup abnormality of a motor (51B, i.e., a fan motor) can be avoided by not starting up the motor (51 B) when a predetermined operation is being performed, and in the predetermined operation a large current flows through a motor (51A, i.e., a compressor motor).