Converter Motor Braking Resistor Shielding for EMI and Heat Dissipation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional converter motors suffer from high error rates due to electromagnetic interference and inefficient heat dissipation, particularly from the braking resistor, which affects the signal electronics and requires a large installation space.
Innovation Solution
The converter motor incorporates a junction box with a metal sheet shielding the braking resistor, a PTC semiconductor material, and a compact design that minimizes interference and heat dissipation, using a metal sheet to shield electromagnetic radiation and a PTC braking resistor for self-protection, while maintaining a decentralized setup without a switch cabinet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the braking resistor is placed near the converter electronics for compact installation, then the installation space is reduced, but electromagnetic interference from the braking resistor increases and causes high error rates in signal electronics
Solution Approach 1:
A metal sheet is introduced as an intermediary shielding element between the braking resistor and the converter electronics. The metal sheet acts as a Faraday cage that blocks electromagnetic fields, allowing the braking resistor to be positioned close to the electronics without causing interference. This mediator enables compact installation while protecting sensitive electronics from harmful electromagnetic radiation.
Solution Approach 2:
The metal sheet provides localized electromagnetic shielding specifically in the region between the braking resistor and the converter electronics. Rather than shielding the entire device, the metal sheet is strategically positioned to block interference only where needed, maintaining compact overall dimensions while protecting the specific vulnerable area containing the signal electronics.
2Reliability
If conventional wire-wound braking resistors are used, then the braking function is achieved, but inductance increases generating low-frequency alternating magnetic fields that interfere with signal electronics
Solution Approach 1:
The braking resistor is changed from a wire-wound construction to a semiconductor-based construction (such as PTC material). This parameter change fundamentally alters the electrical characteristics, reducing inductance to near-zero values. The semiconductor braking resistor maintains the required braking function through resistive heating while eliminating the generation of low-frequency alternating magnetic fields that would interfere with signal electronics.
Solution Approach 2:
The conventional wire-wound resistor structure is replaced with a semiconductor material structure. This substitution changes the physical mechanism from inductive wire winding to semiconductor resistance, eliminating the magnetic field generation associated with wire windings while preserving the braking function through Joule heating in the semiconductor material.
3Device complexity
If the braking resistor dissipates heat directly to the environment, then heat dissipation is simplified, but the heat cannot be dissipated quickly enough requiring larger cooling surfaces
Solution Approach 1:
The heat dissipation function is merged with the electromagnetic shielding function by integrating the metal sheet into the housing structure. The metal sheet serves dual purposes: shielding the electronics from electromagnetic interference and acting as a heat sink to conduct and dissipate heat from the braking resistor. This combination eliminates the need for separate cooling surfaces while improving heat dissipation efficiency.
Solution Approach 2:
The metal sheet acts as a thermal intermediary between the braking resistor and the environment. It provides a large surface area for heat dissipation while maintaining structural integrity and electromagnetic shielding. The metal sheet conducts heat away from the braking resistor efficiently, enabling quick heat dissipation without requiring the braking resistor itself to have large cooling surfaces.
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 reduces electromagnetic interference, minimizes error rates, and allows for efficient heat dissipation, enabling low-error operation and compact installation, while maintaining control over the electric motor's speed.
Implementation Method 1
a metal sheet shields the braking resistor, especially its high-frequency electromagnetic interference radiation
Implementation Method 2
A braking resistor is thermally conductively connected to the bottom part, e.g., for dissipating the heat of the braking resistor to the bottom part
Implementation Method 3
by selecting a PTC material, i.e., a material with a positive temperature coefficient, the braking resistor can be self-protecting
Data Source
AI summary
A converter motor includes a braking resistor, and an electric motor with a junction box. The junction box is formed from a bottom part and a cover placed on the bottom part, and a printed circuit board of the converter is fastened to the cover. A braking resistor is thermally conductively connected to the bottom part and/or fastened on the bottom part, and a metal sheet is connected to the bottom part. The braking resistor is arranged on that side of the metal sheet which is averted from the printed circuit board.