One-Shunt Motor Current Detection Without Rotor Idling Inhibition
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Solution Overview
Problem
In motor control systems using one shunt current detection, the detection of current before motor startup can lead to rotor idling inhibition due to regenerative braking, causing unintended behaviors like deceleration or abnormal noise.
Innovation Solution
A motor controller with an inverter that generates PWM signals with specific energization patterns to minimize rotor idling inhibition, using a current detection unit to calculate offset currents during idle times, allowing for accurate current detection without inhibiting rotor rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current detection is performed using one shunt before motor startup, then current detection accuracy is improved, but rotor idling is inhibited due to regenerative braking
Solution Approach 1:
The patent applies preliminary action by performing current detection using one shunt before motor startup to establish accurate current measurements. This preliminary current detection enables accurate control when the motor starts and the inverter rotates the rotor, while the control method prevents regenerative braking during idle time to avoid inhibiting rotor rotation.
2Reliability
If regenerative braking is applied during rotor idling, then current control accuracy is improved, but unintended behaviors such as deceleration or abnormal noise occur
Solution Approach 1:
The patent applies dynamics by dynamically adjusting the control strategy based on rotor state. During idle time before startup, the inverter is controlled to prevent regenerative braking that would inhibit rotor rotation. Once the motor starts and the inverter rotates the rotor, normal current control with regenerative braking capability is enabled, thus avoiding unintended behaviors while maintaining control accuracy.
Data Source
AI summary
A method for energizing a motor with a rotor by turning on a different portion of all arms, for each energization pattern, among the arms of an inverter, is provided. The method includes generating a PWM signal, for each phase, with a duty cycle of a same value, the PWM signal having a first period length that is defined by a first period during which a portion of the arms is turned on with a first energization pattern, during an idle time of the rotor; a second period during which a portion of the arms is turned on with a second energization pattern, during the idle time; and a third period during which all upper arms or all lower arms, among the arms, are turned on with a third energization pattern, during the idle time. The method includes subtracting, from a first current magnitude or a second current magnitude, a magnitude that is half of a sum of the first current magnitude for a first phase flowing through a current detection unit, which is coupled to a DC side of the inverter, during the first period, and the second current magnitude for the first phase flowing through the current detection unit during the second period, thereby calculating an offset current magnitude for the first phase during the idle time.