Electric Motor Output Control Apparatus Over-Current Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric motor power control systems fail to effectively prevent over-current conditions that can lead to fuse melting, relay welding, and harness damage, as they rely solely on estimating temperature and allowable current values without adequate phase current control.
Innovation Solution
An output control apparatus for electric motors that includes a phase-current instruction-value setting device, draw-current allowable-value storage, phase-current allowable-value setting, and phase-current instruction-value limiting, which sets and limits phase current instruction values based on draw current allowable values and switching element ON time to prevent over-current conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase current sensors are used for precise current control, then over-current prevention is improved, but system cost increases
Solution Approach 1:
The patent segments the control system into two parts: a low-cost draw current control section using temperature estimation for battery protection, and a precise phase current control section using sensors and PWM for motor protection. This segmentation allows the system to achieve comprehensive over-current prevention while keeping the overall cost manageable by applying expensive precise control only where necessary.
Solution Approach 2:
The patent applies different control qualities to different parts of the system: rough draw current control suffices for battery protection, while precise phase current control is applied locally at the motor phase level where over-current damage occurs. This localized application of high-precision control prevents over-current conditions without unnecessarily increasing system-wide costs.
2Reliability
If draw current control is implemented, then battery protection is achieved, but phase current management remains uncontrolled
Solution Approach 1:
The patent segments current management into two independent but coordinated control loops: draw current control for battery protection and phase current control for motor protection. The draw current control maintains battery safety while the phase current control independently manages phase current levels, making phase current management controllable and independent.
Solution Approach 2:
The patent implements feedback control in the phase current management system by using phase current sensors to detect actual phase currents and comparing them with reference values. The controller adjusts PWM duty ratios based on this feedback, enabling closed-loop phase current management that works in coordination with draw current control for comprehensive protection.
Data Source
AI summary
An output control apparatus for an electric motor includes a phase-current instruction-value setting device, a draw-current allowable-value storage device, a phase-current allowable-value setting device, and a phase-current instruction-value limiting device. The draw-current allowable-value storage device is configured to store a draw current allowable value of an electric storage device corresponding to an allowable current value of a system disconnecting-connecting device provided in a power system from the electric storage device to the electric motor. The phase-current allowable-value setting device is configured to set a phase current allowable value based on the draw current allowable value and an ON time of a switching element in a power converter. The phase-current instruction-value limiting device is configured to compare the phase current instruction value with the phase current allowable value to limit the phase current instruction value so as not to exceed the phase current allowable value.