Induction Motor Voltage Compensation for Starting Torque
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Solution Overview
Problem
Induction machines experience motor stoppages or failure during significant load changes or when high torque is required at low speeds due to the limitations of constant flux operation based on the frequency-voltage relationship.
Innovation Solution
An apparatus that includes a first determination unit for command voltage based on a predetermined voltage-frequency relationship, a second determination unit to assess current output, and a third determination unit for voltage compensation, which adjusts the command voltage to improve starting torque by varying the inverter output voltage in response to load conditions, without requiring a rotor position sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant flux operation with predetermined voltage-frequency relationship is used, then the inverter system operates simply and stably under normal conditions, but the motor fails to operate properly when load change is great or high torque is required at low speed
Solution Approach 1:
The patent applies dynamics by transitioning from a static predetermined voltage-frequency relationship to a dynamic voltage command generation that adapts to real-time operating conditions. The controller dynamically adjusts the voltage command based on frequency command, current magnitude, and saturation state, enabling the system to respond to varying load conditions and maintain reliable operation across different operating points.
Solution Approach 2:
The patent implements parameter changes by modifying the voltage command parameters based on the operating state. The controller changes the voltage magnitude and frequency relationship dynamically, using saturation state information to adjust the voltage command and prevent motor stoppage during load changes or starting conditions.
2Device complexity
If voltage-frequency relationship is predetermined, then the control system is simple, but the starting torque is insufficient when high torque is required at low speed
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the voltage command parameters based on the frequency command and saturation state. The controller modifies the voltage magnitude and frequency relationship to provide sufficient starting torque at low speeds while maintaining simplicity in the overall control architecture.
Solution Approach 2:
The patent implements feedback by using current magnitude detection and saturation state information to adjust the voltage command. The controller receives feedback about the operating conditions and uses this information to modify the voltage-frequency relationship, ensuring adequate starting torque without significantly increasing control complexity.
3Stability of the object's composition
If constant flux operation is used, then the voltage-frequency relationship is stable, but motor stoppage occurs during great load changes
Solution Approach 1:
The patent applies dynamics by making the voltage-frequency relationship adaptive rather than fixed. The controller dynamically adjusts the voltage command based on real-time detection of current magnitude and saturation state, allowing the system to maintain stability under normal conditions while adapting to prevent motor stoppage during load changes.
Solution Approach 2:
The patent implements feedback mechanisms by continuously monitoring current magnitude and saturation state, and using this information to adjust the voltage command. This feedback loop maintains the stability of the voltage-frequency relationship under normal operating conditions while preventing motor stoppage during load changes.
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 apparatus stabilizes induction motor operation by enhancing starting torque performance and preventing motor stoppages during load changes, ensuring reliable operation even under demanding conditions.
Implementation Method 1
an inverter (2), which is a device configured to enable a VVVF (Variable Voltage Variable Frequency) operation, can control a torque and speed of a motor
Implementation Method 2
an induction machine is a motor used in various areas ranging from a field including a fan and a pump to a hoisting field including a crane and an elevator
Data Source
Figure 1~2
Figure 3~4
Figure 5~6b
AI summary
An apparatus for controlling an induction machine is disclosed, wherein a magnitude of a current outputted to the induction machine to an inverter is determined by the apparatus to determine a voltage amount that compensates the command voltage in response to the magnitude of the current, and a voltage compensation amount is added to a command voltage determined from a voltage-frequency relationship according to a relevant voltage compensation amount to output a final command voltage.