Synchronous Motor Controller Inertia Estimation for Brake Resistor Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In synchronous motor systems, accurately estimating the inertia of driven objects is challenging, leading to difficulties in determining whether the rotation energy can be safely dissipated by the dynamic brake resistor, which can result in potential damage during emergency stops or failures.
Innovation Solution
A controller that estimates the inertia of driven objects based on feedback speed and current values from the synchronous motor, calculates an allowable maximum speed, and limits the motor speed to prevent excessive energy accumulation in the dynamic brake resistor, thereby protecting it from overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the synchronous motor is immediately stopped using a DB circuit to ensure safety, then the safety requirement is met, but the rotation energy may exceed the allowable energy of the DB resistor causing potential damage
Solution Approach 1:
The controller performs preliminary inertia estimation during normal operation and calculates the maximum allowable speed before emergency stop occurs. By pre-determining the safe speed limit based on estimated inertia and DB resistor energy capacity, the system ensures that when emergency stop is triggered, the motor speed will not exceed the threshold that would cause excessive energy dissipation and damage the DB resistor.
Solution Approach 2:
The system continuously monitors motor speed and compares it against the pre-calculated maximum allowable speed. During emergency stop, this feedback mechanism ensures the speed remains within safe limits. The controller also monitors the energy dissipation in real-time and adjusts the braking action accordingly to prevent DB resistor damage while maintaining safety.
2Reliability
If the inertia of the driven object is accurately estimated to determine safe energy dissipation, then the DB resistor protection is improved, but the complexity of the control system increases
Solution Approach 1:
The system performs self-diagnosis by automatically estimating the inertia of the driven object during normal operation using readily available motor current and speed data. This self-service approach eliminates the need for external measurement devices or manual inertia input, allowing the controller to autonomously determine the safe operating parameters and protect the DB resistor without adding significant external complexity.
Solution Approach 2:
The controller changes the operating parameters by dynamically adjusting the maximum allowable speed based on the estimated inertia. Instead of using a fixed speed limit, the system adapts the speed parameter according to the actual load conditions, enabling optimal protection of the DB resistor while maintaining system simplicity through software-based parameter adjustment.
3Reliability
If the commanded speed is limited to the allowable maximum speed, then the DB resistor is protected from overheating, but the productivity of the system may be reduced
Solution Approach 1:
The system implements dynamic speed limitation rather than a static restriction. The maximum allowable speed is dynamically determined based on the estimated inertia and current operating conditions. During normal operation, the motor can operate at optimal speeds for productivity, while during emergency stop or deceleration phases, the speed is dynamically constrained to ensure the energy dissipation remains within the DB resistor's capacity, thus balancing productivity and protection.
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
The controller effectively limits the synchronous motor's speed to prevent damage to the dynamic brake resistor, ensuring safe operation and reliable emergency stops by accurately estimating inertia and managing energy dissipation.
Implementation Method 1
The DB is configured by a resistor, and converts electric power collected from the electric motor to thermal energy through the DB circuit
Data Source
AI summary
The controller of the synchronous motor of the present invention includes: an allowable energy value acquisition unit (4) which acquires an allowable energy value until which a dynamic brake resistor, which is for short-circuiting the input terminal of the synchronous motor at a time of failure, can bear; an inertia estimation unit (6) which estimates inertia of a driven object based on a speed value and an electric current value; an allowable maximum speed calculation unit (5) which calculates an allowable maximum speed value of the synchronous motor from the inertia and the allowable energy value; and a speed control unit (2) which controls the amplifier for operating the synchronous motor at a predetermined commanded speed, in which the speed control unit (2) acquires the allowable maximum speed value from the allowable maximum speed calculation unit (5), and limits the commanded speed to the allowable maximum speed value or lower.