1.Opening
For electronics & electric components like current transformeror metering transformer which need use for a long time. The PC plastic casing not only serves as insulation protection but also has to withstand assembly, transportation and environmental stresses. Once cracks occur, it may cause water ingress, creepage, metering drift, and even power outages.
Therefore, this article will mainly introduces the structure of HK current transformer, the causes of problems and improvement methods toavoid the occurrence of cracks as much as possible.
2.Introduction to the product structure and design
The mainstream HK push-button open-close type current transformer is composed of a silicon steel core , 99.9% pure copper coils, red copper terminal blocks and springs from the inside out. The product is divided into a U-shaped part and an I-shaped part, which are connected by hinges and opened with closed by buttons. Among them, the I-shaped part is clamped and fixed by the iron core at the connection and the button by a spring. These structural key points determine that the casing will be subjected to relatively large assembly and elastic energy storage release stresses locally.
3. Scenarios where cracks may occur
Be under the blazing sun for quite a long time: after beingunder the sun for a long time, this PC materials will graduallybecome brittle.
Improper logistics transportation and storage: Shaking, bumping and stacking during transportation can trigger hidden or through cracks at the stress concentration points of the shell.
Long-term internal force compression of I-shaped part springs: The continuous external support of the spring will keep the I-shaped part in a local state of being "stretched apart" under force. Over time, this can cause cracks.
4. Case studies and cause analysis
You can see cases in the following images. The cracking is concentrated at the button and the connection points at the I shape part. These two points are not only the force transmission points for opening and closing but also there are hotspots for stress concentration.
Directly reason: When after Ultrasonic die casting, the "tensile strength" formed by interfacial bonding/interlocking is insufficient and cannot counteract the outward force of the spring for a long time, resulting in the gradual cracking of the shell.
5. The corrective way adopted by ASCT
Inaddition to the above the basic HK current transformer materials, we also taken some measures as the following.
Upgrade materials: Replace the PC with a material system that has higher adhesion/toughness and is friendly to ultrasonic welding to enhance the crack resistance of the interface.
Optimize Structure: Check the preload and clearance to avoid long-term "oversaturation" of the support force. Thicken/reinforce the periphery of the spring seat but keep the transition between thick and thin smooth to reduce the stress gradient.
For the transformers made of the above-mentioned PC materials, we have also obtained the following certifications.
6.Contact
If you want to know more information about current transformer, please contact us.
E-mail:bethy@heyiele.com Telephone number: 86-13968747975
