Motor Inverter Idling Detection Using Inductive Kickback
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Solution Overview
Problem
Existing methods for detecting motor idling are inefficient, particularly in short time frames, and often require the use of position sensors or are limited by low speed-induced voltage detection issues.
Innovation Solution
A motor drive control device that includes a control circuit, a drive circuit with an inverter circuit, and a phase voltage detection circuit. The control circuit generates an idling control signal to switch the inverter circuit's switch state, allowing for the detection of idling based on phase voltage generated by inductive kickback when the induced current path is blocked.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the conventional method using zero-cross detection of differential voltage is employed, then the device configuration can be simplified without position sensors, but the detection time becomes excessively long and the minimum detectable rotation speed is limited
Solution Approach 1:
The invention changes the detection parameter from zero-cross voltage detection to induced current detection. By monitoring the current flowing through the motor windings during idle rotation, the system can detect idling states much faster while maintaining simplicity in device configuration without requiring position sensors.
Solution Approach 2:
The invention substitutes the voltage-based detection mechanism with a current-based detection mechanism. This replacement allows for faster response times because current detection can identify induced currents from rotor inertia immediately, whereas voltage detection requires waiting for zero-cross events that may not occur frequently at low speeds.
2Device complexity
If the conventional zero-cross detection method is used, then the device configuration is simplified, but the detection accuracy deteriorates at low speeds due to small induced voltage
Solution Approach 1:
The invention changes the detection parameter from voltage to current. By detecting the current flowing through the motor windings during idle rotation, the system achieves high detection accuracy even at low speeds where induced voltage is minimal. The current detection method is more sensitive to the magnetic field changes caused by rotor inertia at low rotation speeds.
3Measurement precision
If winding resistance measurement and initial position detection are performed when the motor is idling, then the measurement accuracy deteriorates due to periodic induced voltage and current
Solution Approach 1:
The invention performs preliminary detection of the idling state by monitoring induced current before attempting winding resistance measurement or initial position detection. By first identifying that the motor is in an idle state through current detection, the system can then schedule the resistance measurement and position detection operations for a later time when the motor is properly driven, avoiding the periodic voltage and current interference that would otherwise degrade measurement accuracy.
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
Enables stable and rapid detection of motor idling without using a position sensor, improving detection accuracy and reducing the time required for idling determination.
Implementation Method 1
when the rotor of the motor is idling, an induced electromotive force is generated, and then when the motor coil and the inverter circuit do not form a closed circuit, an induced voltage is periodically generated at the motor coil (winding), and when the motor coil and the inverter circuit form a closed circuit, an induced current is periodically generated at the motor coil
Implementation Method 2
determines idling of the motor based on a phase voltage generated at the phase voltage detection circuit by an inductive kickback generated at the inverter circuit when a path of the induced current is blocked
Data Source
AI summary
A motor drive control device includes: a control circuit configured to generate a drive control signal; a drive circuit including an inverter circuit including a switch provided corresponding to each phase of coil of the motor, the drive circuit being configured to rotate a rotor of the motor by alternately turning the switch on and off in response to the drive control signal; and a phase voltage detection circuit configured to detect a phase voltage generated between the inverter circuit and each phase of coil of the motor. The control circuit generates an idling control signal and switches a switch state of the inverter circuit to generate a current circulating between each phase of coil of the motor and the inverter circuit when the rotor of the motor is idling, and then determines idling of the motor based on a phase voltage generated at the phase voltage detection circuit by an inductive kickback generated when a path of the current is blocked.