Motor control systems
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Solution Overview
Problem
Induction motors operating from single-phase AC voltage face inefficiencies in starting and running due to the need for additional power to generate a rotating magnetic field, leading to increased energy consumption and potential overheating, especially in applications like refrigeration compressors where frequent starting and stopping occurs.
Innovation Solution
A control system with an electronic controller that manages power to both the main and auxiliary windings of the induction motor, using current and temperature sensors to optimize energy consumption by varying the motor's operation based on thermal demand, reducing the need for separate starting and running modes, and incorporating a boost function to enhance torque and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a starting winding is powered at high level to start the motor, then the motor can generate sufficient rotating magnetic field to start, but energy consumption increases and overheating risk occurs during frequent starting
Solution Approach 1:
The patent applies dynamics by making the starting winding power level variable rather than fixed. The controller dynamically adjusts the power supplied to the starting winding based on real-time motor speed feedback. During startup, high power is applied to generate sufficient rotating magnetic field, then power is gradually reduced as motor speed increases, optimizing energy consumption while ensuring reliable starting capability.
Solution Approach 2:
The patent implements periodic action through pulsed or cyclic power application to the starting winding. Instead of continuous high-level power during entire operation, the controller applies power in controlled periods - high power during initial startup phase, then reduces or interrupts power once motor reaches certain speed thresholds, creating a periodic on-off or variable-power pattern that balances starting reliability with energy conservation.
2Use of energy by moving object
If the auxiliary winding is disconnected after motor reaches stable speed, then energy consumption reduces, but the motor cannot respond to increasing mechanical load
Solution Approach 1:
The patent applies feedback by using a speed sensor to continuously monitor motor speed and provide this information back to the controller. Based on the feedback signal indicating motor operating conditions, the controller intelligently decides when to disconnect or reconnect the auxiliary winding. When speed indicates stable operation, auxiliary winding is disconnected to save energy; when load increase is detected through speed deviation, auxiliary winding is reconnected to provide additional torque, thus adapting to load changes while managing energy consumption.
Solution Approach 2:
The patent makes the auxiliary winding connection status dynamic rather than static. Instead of permanently disconnecting the auxiliary winding after startup, the controller dynamically controls its connection based on real-time motor operating conditions. The auxiliary winding can be reconnected if load increase is detected, creating a dynamic on-off pattern that adapts to varying mechanical demands while minimizing unnecessary energy consumption during light-load operation.
3Force
If the motor is designed for maximum output torque, then sufficient torque is available for peak demand, but efficiency is reduced during part-load operation
Solution Approach 1:
The patent applies partial action by providing torque capability in excess of normal operating requirements only when needed. The motor is designed with auxiliary winding capability that can deliver maximum torque for peak demands, but this full torque capability is not continuously applied. Instead, the controller applies partial power to the auxiliary winding only when load conditions require additional torque, using full torque capability intermittently rather than continuously, thus maintaining peak performance availability while improving part-load efficiency.
Solution Approach 2:
The patent implements periodic action in torque delivery by cycling the auxiliary winding connection based on load demands. During normal part-load operation, only the main winding operates for efficient energy consumption. When peak torque is required, the auxiliary winding is periodically reconnected to provide excessive torque capability, then disconnected when demand decreases. This periodic application of full torque capability allows the motor to meet peak demands while maintaining high efficiency during extended periods of lower load operation.
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 system reduces energy consumption by optimizing the number of starts and runtime of the compressor, minimizing energy waste, and enhancing motor efficiency by adjusting power distribution dynamically based on load conditions, thereby reducing overheating risks and improving overall performance.
Implementation Method 1
the phase of the current in each winding depends on the ratio of its inductance to the total circuit resistance (winding inductance plus any external series inductance) so the relatively higher inductance to resistance of the main winding causes the current in the main winding to lag in relation to current in the starting winding. This phase difference of current, though less than 90°, causes the net magnetic field to have a rotating component which starts the motor.
Implementation Method 2
Using a capacitor in this connection provides a large phase shift between the current in the Main winding and the current in the Auxiliary winding. This large phase difference ensures that the auxiliary winding current increases the available torque and overall efficiency of the motor
Implementation Method 3
The PTC is cold before starting, so has a relatively low resistance. This allows a high current to flow in the Auxiliary winding but also the resistance of the PTC adds to that of the winding to increase the phase difference between Main and Auxiliary winding current. The large current flowing through the resistance of the PTC causes it to heat, after a time reaching a switching temperature above which the resistance rises rapidly.
Data Source
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AI summary
We describe a control system for a refrigerator compressor, the refrigerator compressor comprising an induction motor having a main winding and a starting/boost winding, the motor being energised from a single phase of an ac mains power supply, the control system comprising: an electronic controller having a power supply derived from said ac mains power supply; a current/voltage sense signal input coupled to said electronic controller to input a signal dependent on a current drawn by said motor or a voltage induced in a winding of said motor; a first controllable switch having a control connection coupled to said electronic controller to control application of power from said ac mains power supply to said main winding; a second controllable switch having a control connection coupled to said electronic controller to control application of power from said ac mains power supply to said starting/boost winding; and a temperature sense input coupled to said electronic controller to receive a temperature sense signal sensing a temperature of a cooled zone of a refrigerator; wherein said electronic controller is configured to control said first and second controllable switches responsive to both said current sense signal and said temperature sense signal to control: i) starting/boost of said compressor; ii) running of said compressor to control said temperature of said cooled zone towards a target temperature value; and, optionally, iii) an average energy consumption of said compressor.