Multi-Motor Inverter Control With Fewer Current Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The use of multiple inverters for controlling multiple permanent magnet synchronous motors in air conditioners increases size and cost, and existing position sensor-less control methods require multiple current sensors, leading to high costs, especially for three-phase motors.
Innovation Solution
A motor control device that applies position sensor-less control by using a single inverter to control multiple motors, where current sensors are provided for n-1 motors, and the motor current of the remaining motor is calculated using detection values from these sensors and an inverter current sensor, eliminating the need for additional current sensors and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If one inverter is used to control multiple PM motors, then the size and cost of the air conditioner are reduced, but it becomes necessary to use position sensor-less control which traditionally requires multiple current sensors
Solution Approach 1:
The patent merges the control of multiple PM motors into a single inverter system, consolidating what would traditionally require separate inverters for each motor. This combining approach reduces the overall size and cost while managing the complexity through shared control architecture and sensor utilization strategies.
Solution Approach 2:
The patent makes the current sensors serve multiple functions by using them for both individual motor control and position estimation in the sensor-less control system. The same hardware resources are utilized for multiple purposes, eliminating the need for additional sensors while maintaining control capability across multiple motors.
2Adaptability or versatility
If position sensor-less control is implemented with multiple current sensors for three-phase motors, then sensor-less control is achieved, but the cost of the device increases significantly
Solution Approach 1:
The patent makes the current sensors serve multiple functions by using them for both individual motor control and position estimation in the sensor-less control system. The same hardware resources are utilized for multiple purposes, eliminating the need for additional sensors while maintaining control capability across multiple motors.
Solution Approach 2:
The system uses its own existing current sensors to provide the position information that would traditionally require separate position sensors. The current sensors serve themselves dual purposes, generating both control signals and position estimates without requiring external additional components.
3Measurement precision
If a rotation sensor is used for PM motor control, then precise control is achieved, but the device size and cost increase
Solution Approach 1:
The patent replaces the mechanical position sensor system with an electronic estimation system that calculates rotor position from current measurements. This substitution eliminates the need for physical sensors and associated wiring, reducing device size while maintaining control precision through computational methods.
Solution Approach 2:
The patent introduces a computational intermediary (the control unit's position estimation algorithm) that derives position information from current measurements. This intermediary process acts as a mediator between the electrical measurements and the control decisions, replacing direct mechanical sensing with an information-processing approach.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A motor control device (100) includes an inverter (4) configured by a plurality of arms (4a), a smoothing means (3) supplying a direct-current voltage to the inverter (4), a shunt resistor (7u, 7v, 7w) inserted between a lower-arm switching element for each phase of the inverter (4) and a negative-electrode side of the smoothing means (3), a master motor current sensor (9) outputting a voltage according to a current flowing in a first motor (51) connected in parallel to the inverter (4), and a computing unit (6) generating driving signals for a plurality of switching elements based on an output of the master motor current sensor (9) and an output corresponding to a voltage drop on the shunt resistor (7u, 7v, 7w).