Dynamic Brake Resistor Cooling During Standby Motor Rotation
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Solution Overview
Problem
The reliability of motor drive devices is compromised due to heat generated by the operation of a dynamic brake when the motor is controlled to be in a standby state, especially when it rotates due to external forces, as the estimated calorific value becomes too small, leading to improper operation.
Innovation Solution
A motor drive device with a dynamic brake that includes a resistor to consume kinetic energy and stop the motor, where the rotation speed of a secondary motor is controlled to match the primary motor's speed to effectively cool the resistors and heat generators, preventing overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dynamic brake is operated to stop the motor when the motor is controlled to be in a standby state, then the reliability of the entire device is improved, but the resistor generates heat due to power generation energy from external force rotation, causing cooling requirements and potential reliability decrease
Solution Approach 1:
The control device determines whether the motor is rotating due to external force before operating the dynamic brake. By detecting the rotation cause in advance (through current detection and rotation direction determination), the system performs preliminary assessment to avoid unnecessary dynamic brake operation during external force rotation, thereby preventing unwanted heat generation in the resistor while maintaining reliability through targeted brake application when needed
2Use of energy by moving object
If the technique for controlling the rotation speed of the motor disclosed in PTL 1 is applied, then energy consumption is optimized, but the estimated calorific value may be too small when the motor moves due to external force (because the control current is zero), leading to improper motor operation and decreased reliability
Solution Approach 1:
The control device continuously detects the rotation direction of the motor and the direction of control current flow during standby state. By establishing feedback mechanisms that monitor both rotation direction and current direction, the system can distinguish between motor-driven rotation and external force-driven rotation, enabling reliable operation decisions even when control current is zero, thus maintaining both energy efficiency and operational reliability
3Reliability
If the dynamic brake operates during external force rotation, then the motor can be stopped reliably, but the resistor consumes heat from kinetic energy continuously, requiring cooling and reducing overall system efficiency
Solution Approach 1:
The control device uses the motor's own electrical characteristics (current flow direction and rotation direction relationship) to identify the cause of rotation. By leveraging the self-diagnostic capability of the motor's electrical signals, the system determines whether external force is acting on the motor without requiring additional sensors or complex external monitoring, enabling intelligent dynamic brake control that prevents unnecessary energy loss while maintaining stopping reliability
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
Prevents a decrease in reliability by effectively cooling the dynamic brake resistors and heat generators, ensuring the motor drive device operates reliably even when the primary motor rotates due to external forces.
Implementation Method 1
The dynamic brake includes a resistor electrically connected between terminals of the first motor, and is configured to short-circuit the terminals to cause the resistor to consume heat of kinetic energy of the first motor to stop the first motor
Data Source
AI summary
A decrease in reliability due to heat during operation of a dynamic brake is prevented. Motor drive device includes first controller, second controller, and dynamic brake. First controller controls first motor. Second controller controls second motor. Second motor cools at least one of heat generator and heat radiator. Dynamic brake, which includes resistors connected among terminals of first motor, short-circuits terminals to cause resistors to consume kinetic energy of first motor to stop first motor. While first motor is controlled to be in a standby state, second controller changes the rotation speed of second motor according to the rotation speed of first motor. Heat generator includes resistors.