Variable Speed Drive Precharging Resistor Deceleration Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Variable speed drives with diode bridge rectifier stages struggle to efficiently manage electrical energy feedback during motor deceleration, leading to prolonged deceleration times without dedicated braking devices.
Innovation Solution
A control method that utilizes a precharging device with a resistor and switch connected in series with a bus capacitor, controlling current through the resistor to dissipate energy and optimize deceleration, while maintaining a constant average voltage and limiting voltage oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a braking resistor is used to dissipate electrical energy during motor deceleration, then the deceleration time is reduced, but the device complexity and cost increase due to additional braking transistors
Solution Approach 1:
The precharging resistor, originally designed solely for inrush current limitation during startup, is made to serve dual purposes: it continues to limit inrush current during startup while also functioning as an energy dissipation element during motor deceleration. This multi-functionality eliminates the need for separate braking components, resolving the contradiction between reduced deceleration time and device complexity
Solution Approach 2:
The system uses its own existing precharging resistor to handle the energy dissipation during deceleration, rather than requiring external braking components. The precharging resistor serves the system's braking needs without requiring additional dedicated braking devices, thus reducing device complexity while maintaining effective deceleration
2Device complexity
If the deceleration trajectory is modified to limit electrical energy feedback, then device complexity is reduced, but the deceleration time increases due to reliance on natural losses
Solution Approach 1:
The system utilizes its own precharging resistor to actively dissipate regenerative energy during deceleration, rather than relying solely on natural mechanical and electrical losses. This self-service approach allows the system to maintain simplicity while achieving faster deceleration by actively controlling energy dissipation through the existing resistor
3Loss of time
If current through the precharging resistor is increased to maximize energy dissipation, then deceleration time is reduced, but voltage oscillations on the DC bus increase
Solution Approach 1:
The control unit continuously monitors the voltage on the DC bus and uses this feedback to dynamically adjust the switching of the precharging resistor. When voltage oscillations are detected, the control unit modulates the resistor's engagement to dampen oscillations while maintaining effective energy dissipation, thus resolving the contradiction between fast deceleration and voltage stability
Solution Approach 2:
The system dynamically controls the switching of the precharging resistor based on real-time operating conditions and voltage levels. Rather than using a fixed switching strategy, the dynamic adjustment of the resistor's engagement allows the system to optimize both deceleration speed and voltage stability across different operating scenarios
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 approach reduces deceleration time by maximizing losses within the drive system, avoiding damage to components and improving motor control performance without the need for dedicated braking devices.
Implementation Method 1
A control method implemented in a variable speed drive... controlling the current flowing in the precharging resistor during a deceleration of the motor... to dissipate the electrical energy returned by the electric motor during its deceleration
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
The invention relates to a control method implemented in a speed variator connected to an electric motor, said speed variator comprising: - a rectifier stage (REC), - a DC power supply bus connected to the rectifier stage (REC), - a bus capacitor (C), - an inverter stage (INV) connected downstream of the DC power supply bus and comprising several switching arms, - a pre-charge device connected in series with the bus capacitor (C) and comprising a pre-charge resistor (R) and a switch (Sw) connected in parallel with said pre-charge resistor (R), characterized in that the method consists of controlling the inverter stage (INV) so as to control the current (I) flowing through the pre-charge resistor (R) during a deceleration of the motor, said current (I) being controlled taking into account the voltage (Vbus) of the DC power supply bus and an optimal reference value (Vbus_ref).