Synchronous Motor Protection Device Dynamic Braking Control
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Solution Overview
Problem
The existing dynamic brake circuits for synchronous motors face challenges in selecting an appropriate resistance value for resistors, as lower values can lead to overcurrent and demagnetization, while higher values risk exceeding the withstand voltage of the driving device, posing a risk to both the motor and the motor driving device.
Innovation Solution
A protection device with a switching unit, dynamic brake circuit, and control device that controls the short-circuiting of windings via resistors and switches, allowing for the appropriate selection of resistance values to protect the synchronous motor and motor driving device by ensuring safe short-circuiting and disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the resistance value of the resistor in the dynamic brake circuit is made smaller, then the braking force on the motor increases, but the magnets of the motor rotor may be demagnetized or the driving device may be destroyed due to overcurrent
Solution Approach 1:
The invention divides the braking process into two distinct phases: first phase with lower resistance for strong braking, and second phase with higher resistance for safe current dissipation. This segmentation allows the system to achieve both strong braking force and protection against demagnetization by switching between different resistance values at appropriate times
Solution Approach 2:
The invention dynamically changes the resistance value during the braking process by switching between multiple resistors. The resistance is not fixed but adapts during operation - starting with lower resistance for immediate braking effect, then transitioning to higher resistance to dissipate remaining energy safely, thus resolving the contradiction between braking force and demagnetization risk
2Reliability
If the resistance value of the resistor in the dynamic brake circuit is made greater, then the risk of overcurrent and demagnetization decreases, but the potential difference during short circuit between the power lines for different phases increases, risking exceedance of the withstand voltage of the driving device
Solution Approach 1:
The braking process is segmented into two phases with different resistance values. The first phase uses lower resistance to limit potential difference and protect the driving device voltage withstand capability. The second phase uses higher resistance to safely dissipate energy. This segmentation resolves the contradiction by applying appropriate resistance values at different stages
Solution Approach 2:
The invention performs preliminary action by first connecting the lower resistance resistor before the higher resistance resistor during the braking process. This preliminary connection of lower resistance prevents excessive potential difference from developing across the driving device, thereby protecting it from voltage exceedance before the higher resistance is engaged
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 the selection of optimal resistance values in the dynamic brake circuit, effectively protecting the synchronous motor and motor driving device by controlling short-circuit currents and preventing voltage exceedance, thus ensuring reliable operation and safety.
Implementation Method 1
dynamic brake circuits have been widely used for emergency stop of a motor driven by a motor driving device. The dynamic brake circuit is a circuit that short-circuits multiple windings of a motor via resistors to convert rotational energy into Joule heat to brake the rotation of the motor.
Data Source
AI summary
A protection device provided between a synchronous motor having a plurality of windings and a motor driving device for driving the synchronous motor includes: a switching unit for making and breaking the connection between the motor driving device and the synchronous motor; a dynamic brake circuit including resistors and switches, to short-circuit the plurality of windings between the switching unit and the synchronous motor via the resistors; and a control device for controlling the switching unit and the dynamic brake circuit. The control device controls the switches in the dynamic brake circuit to short-circuit the plurality of windings, and then controls the switching unit to cut off the connection between the motor driving device and the synchronous motor.