Motor Drive Dynamic Braking Circuit Design
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Solution Overview
Problem
Existing motor driving devices face issues with applying dynamic brakes, as semiconductor switches inside the inverter can break when the inverter fails, leading to heat generation and increased costs, and mechanical switches experience arc discharges during dynamic braking, reducing their lifespan.
Innovation Solution
A motor driving device with a dynamic braking circuit that includes a mechanical switch and a semiconductor switch connected in parallel, along with a first impedance circuit in series with the semiconductor switch, allowing for controlled short circuits between motor windings to apply dynamic brakes without overheating the semiconductor switches and minimizing arc discharges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If semiconductor switches inside the inverter are used for dynamic braking, then the dynamic brake can be applied, but the semiconductor switches generate heat and may break down, reducing reliability
Solution Approach 1:
The patent extracts the dynamic braking function from the inverter's semiconductor switches by providing a separate dynamic braking circuit with its own switching device. This separation removes the heat-generating dynamic braking operation from the inverter's semiconductor switches, preventing their breakdown and improving overall system reliability.
Solution Approach 2:
The patent introduces a separate switching device as an intermediary component dedicated to dynamic braking operations. This intermediary switching device handles the high-current dynamic braking function, protecting the inverter's semiconductor switches from excessive heat and current stress.
2Reliability
If high-capacity semiconductor switches are used to avoid breakdowns, then reliability improves, but production cost and device size increase
Solution Approach 1:
The patent extracts the dynamic braking function from the inverter's semiconductor switches, allowing the use of smaller, lower-capacity switches in the inverter while maintaining reliability. The separate dynamic braking circuit handles high-power operations independently.
Solution Approach 2:
The separate switching device serves multiple functions: it enables dynamic braking operations and can be used in conjunction with the inverter's semiconductor switches. This multi-functionality allows the system to achieve high reliability without requiring oversized semiconductor switches throughout the entire system.
3Device complexity
If mechanical switch is used for dynamic braking, then the structure is simple, but arc discharge occurs when the switch is turned on, causing contact point wear and reducing lifespan
Solution Approach 1:
The patent replaces the purely mechanical switching mechanism with a hybrid system that uses a semiconductor-based switching device for dynamic braking. This substitution eliminates arc discharge at the mechanical contact points, preventing wear and extending the lifespan of the switching components while maintaining structural simplicity.
4Temperature
If semiconductor switches are not turned on during dynamic braking, then heat generation is avoided, but arc discharge occurs at mechanical switch contact points
Solution Approach 1:
The patent introduces a separate switching device as an intermediary that handles the high-current dynamic braking function. This intermediary component can be designed to minimize both heat generation in semiconductor switches and arc discharge at mechanical contact points, resolving the conflict between these two harmful effects.
Solution Approach 2:
The patent segments the switching function into separate components: the inverter's semiconductor switches for normal operation and a dedicated switching device for dynamic braking. This segmentation allows each component to be optimized for its specific function, reducing both heat generation and arc discharge.
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
This configuration extends the lifespan of the motor driving device by preventing heat generation in semiconductor switches and reducing wear on mechanical switches, enabling efficient dynamic braking with lower-rated, smaller switches.
Implementation Method 1
a first impedance circuit connected to the semiconductor switch in series... preventing heat generation in semiconductor switches
Implementation Method 2
mechanical switches experience arc discharges during dynamic braking, reducing their lifespan
Data Source
Figure 1~2
Figure 3
Figure 4(a)~4(b)
AI summary
A long-life motor driving device is realized. A motor driving device (11) includes: a motor driving circuit (3) configured to supply an alternating electric current to a motor (2); and a dynamic braking circuit (4). The dynamic braking circuit includes: a mechanical switch (SW2) configured to cause a short circuit between windings corresponding to respective two phases; a semiconductor switch (SW1) connected to the mechanical switch in parallel and configured to cause a short circuit between the windings corresponding to the respective two phases; and a first impedance circuit (Z1) connected to the semiconductor switch in series.