External Unit PTC Thermistor Motor EMC Noise
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Solution Overview
Problem
The existing motor designs with PTC thermistors in the power supply line suffer from inadequate electromagnetic compatibility (EMC) performance due to the hole in the bottom plate, allowing switching noise to radiate as electromagnetic compatibility noise.
Innovation Solution
An external unit with a holder, a flat-plate PTC thermistor, and terminals is mounted on the motor body, where the PTC thermistor is arranged perpendicular to the rotary shaft direction, and the terminals are connected to improve EMC performance by reducing noise radiation and allowing for efficient heat sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a hole is opened in the bottom plate to install the PTC thermistor, then the PTC thermistor can be arranged in the power supply line, but EMC noise performance deteriorates due to radiation noise from the hole
Solution Approach 1:
An external unit with a holder is introduced as an intermediary component. The PTC thermistor is mounted on the holder, which is then attached to the motor housing. This mediator allows the PTC thermistor to be installed without opening the bottom plate, thus preventing EMC noise radiation while achieving the power supply line protection function.
Solution Approach 2:
The installation structure is segmented into separate components: the holder as a mounting platform, the PTC thermistor as the protective element, and the external unit as the integration interface. This segmentation allows the PTC thermistor to be mounted externally on the holder rather than requiring a hole in the bottom plate, solving the EMC noise problem while maintaining ease of installation.
2Object-affected harmful factors
If the PTC thermistor is arranged perpendicular to the rotary shaft direction, then EMC performance improves by reducing noise radiation, but the space requirement increases
Solution Approach 1:
The PTC thermistor is oriented perpendicular to the rotary shaft direction, changing the dimensional arrangement from the conventional axial orientation. This dimensional change allows the thermistor to be mounted on the holder in a direction that reduces EMC noise radiation while the holder's design accommodates this orientation within available space.
3Ease of manufacture
If a plate-type PTC thermistor is used, then manufacturing cost decreases and assembly simplifies, but the terminal connection complexity increases
Solution Approach 1:
The holder integrates multiple functions: it serves as the mounting platform for the plate-type PTC thermistor, provides the pressing means for electrical contact, and includes the pressing terminal that connects to the motor terminal. By merging these functions into a single integrated holder structure, the patent simplifies overall assembly despite the increased terminal connection complexity of plate-type thermistors.
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 enhances EMC performance, improves heat detection accuracy, and allows for efficient manufacturing without compromising motor design, enabling the use of a plate-type PTC thermistor that reduces manufacturing costs and simplifies assembly.
Implementation Method 1
a PTC (Positive Temperature Coefficient) thermistor is provided in the power supply line of the motor
Implementation Method 2
the second terminal has a pressing means in contact with the surface of the PTC thermistor, and the pressing means presses the PTC thermistor onto the holder
Data Source
AI summary
In accordance with one aspect of the present disclosure, an external unit used by being mounted on a bottom part of a motor body having at least two motor terminals has a holder, a PTC thermistor arranged on the holder, a first terminal connected to the PTC thermistor, a part of the first terminal exposed to an outside of the holder, and a second terminal electrically connected to the first terminal through the PTC thermistor and electrically connected to one of the motor terminals. The PTC thermistor is flat-plate shaped, and a surface of the PTC thermistor is directed toward a rotary shaft direction of the motor.