Multi-Motor Inverter Switching for Phase Synchronization Stability
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Solution Overview
Problem
Existing motor driving systems for multiple permanent magnet synchronous motors using a single inverter face challenges in preventing hunting and step-out due to phase differences between motors, particularly for interior magnet type motors where reluctance torque is generated, leading to increased current requirements and potential operational disruptions.
Innovation Solution
A motor driving apparatus with a connection switching device that adjusts the number of motors connected to the inverter to change impedance, ensuring that the phase inductances and induced voltages of all motors are synchronized, thereby maintaining identical phase relations and preventing excessive current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lead angle of the current is increased to increase the current and prevent hunting and step-out, then the output torque of the motor is increased, but the current for outputting the same torque is reduced, which increases the possibility of hunting or step-out
Solution Approach 1:
The patent changes the impedance parameter by adjusting the number of motors connected to the inverter. By dynamically changing the motor configuration (single motor or dual motor operation), the system optimizes the current characteristics and impedance matching, preventing hunting and step-out without requiring excessive current increases.
2Adaptability or versatility
If multiple motors are driven by a common inverter, then the system can operate under varying load conditions, but phase differences between motors cause hunting and step-out
Solution Approach 1:
The patent implements dynamic switching between single motor and dual motor operation modes. The connection switching device dynamically adjusts which motors are connected to the inverter based on load conditions, ensuring optimal phase synchronization and impedance matching for each operating mode, thereby preventing hunting and step-out while maintaining adaptability.
Solution Approach 2:
The system changes the operational parameter of motor quantity (one or two motors) connected to the inverter. This parameter change allows the system to optimize impedance and phase relations for different load conditions, preventing phase synchronization issues while maintaining operational versatility.
3Power
If interior magnet type motors are used to generate reluctance torque, then the output torque is increased, but the current for the same torque is reduced, increasing the possibility of hunting or step-out
Solution Approach 1:
The patent changes the impedance parameter by adjusting the number of motors connected to the inverter. This parameter change optimizes the current characteristics for interior magnet type motors, ensuring stable operation and preventing hunting and step-out while maintaining the high torque output capability.
Data Source
AI summary
In a motor driving apparatus having an inverter which can drive n (n being an integer not smaller than 2) motors each having a permanent magnet in its rotor, and a connection switching device for switching the connection state of the n motors, the connection switching device is operated to change the number of the motors connected to the inverter thereby to change the impedance as seen from the inverter towards the motors. When i (i being any of 2 to n) motors among the n motors are concurrently driven by the inverter, the voltage outputted by the inverter may be controlled such that the inductance values of the i motors are identical. It is possible to prevent hunting and step-out due to the phase difference between the motors driven by the inverter.