In the transmission and transformation of electrical energy in power systems, transformers are core hub devices, and their selection directly determines the safety, stability, economy, and operation and maintenance costs of facility power supply. Dry-type transformers and oil-immersed transformers, as the two mainstream types in current industrial and civil fields, have fundamental differences in insulation medium, cooling methods, and performance characteristics, and each has different application scenarios. This article delves into the differences between the two in terms of core structure, key performance, and applicable scenarios from three dimensions and provides a scientific selection method to assist enterprises and facility managers in making the optimal decision that aligns with their specific needs.

 

I. Core Structural and Operational Principle Differences

The core difference between dry-type transformers and oil-immersed transformers lies in the insulation medium and cooling methods, which directly determine their structural design, operational characteristics, applicable scope, and are the primary considerations in selection.

A. Dry-Type Transformers
Dry-type transformers use air (or inert gas) as the insulation medium, where the windings are solidly insulated with epoxy resin casting, Nomex paper wrapping, among others. They do not require insulating oil for cooling and insulation but rely on the solid insulation processes. The core structure consists of iron cores, windings, insulation systems, cooling systems, and accessories. Their operation principle is based on the electromagnetic induction law: high-voltage windings connected to an AC power supply generate an alternating magnetic field, which is transferred to the low-voltage windings through the iron core. Heat dissipation is achieved through natural airflow or forced air cooling (with the addition of axial-flow fans), eliminating the need for additional cooling medium circulation systems.

 

Mainstream dry-type transformers are divided into epoxy resin cast and impregnated types. Epoxy resin cast transformers, known for high insulation strength, good mechanical properties, and dust and moisture resistance, are the most widely used type in the market adaptable to various complex environments. The impregnated type, with excellent heat dissipation and lightweight structure, is suitable for clean environments with high heat dissipation requirements.

 

B. Oil-Immersed Transformers
Oil-immersed transformers use mineral insulation oil (or synthetic insulation oil) as the core insulation and cooling medium. The iron core and windings are completely immersed in a sealed oil tank. In addition to the iron core and windings, the core structure includes components such as the oil tank, oil cushion, radiator, gas relay, pressure release valve, and other specialized accessories. While their operational principle is similar to dry-type transformers, heat transfer relies on natural convection or forced circulation of the insulation oil (driven by oil pumps), dissipating heat to the air through the oil tank walls and radiator. Insulation oil also functions in arc suppression, air isolation, and retarding insulation aging, ensuring long-term stable operation of the equipment.

Oil-immersed transformers have three cooling methods: oil-immersed self-cooling, oil-immersed air cooling, and forced oil circulation air/water cooling. They respectively cater to small-capacity, medium-capacity, and large-capacity, high-load scenarios. Notably, forced oil circulation significantly enhances heat dissipation efficiency and meets the operational requirements of ultra-large capacity equipment.

 

II. Comparative Analysis of Key Performance Parameters (Professional Dimension)

Starting from the core requirements of facility operation and combining with industry standards, the following professional comparisons of both types across four key dimensions — safety performance, operation and maintenance costs, environmental adaptability, and electrical performance — present a quantitative reference for selection:

A. Safety Performance
Dry-type transformers have a natural fire and explosion advantage due to the absence of combustible insulating oil. They do not produce toxic gases during operation and are unlikely to cause fires even in the event of a short-circuit fault. They reach fireproof levels of F and H (resistant to temperatures of 180°C), eliminating the need for additional fire or leakage prevention facilities, making them suitable for locations with high occupancy or high fire safety requirements.

The insulating oil of oil-immersed transformers is combustible. In the event of a damaged oil tank or seal failure causing oil leakage, exposure to high temperatures or ignition sources can lead to combustion and explosion, posing certain safety risks. Therefore, during installation, safety facilities such as oil reservoirs and fire extinguishing devices need to be equipped. They are unsuitable for installation in areas with high occupancies or in environments prone to combustion and explosions. Their insulation grades typically range from Class A (resistant to temperatures of 105°C), lower than that of dry-type transformers.

 

B. Operation and Maintenance Costs
The operational process of dry-type transformers is straightforward. Without the need for oil quality testing or oil changes, only regular dust removal, inspection of terminal connections, and winding insulation status are required. This leads to lower annual maintenance costs and extends maintenance intervals to 6-12 months, suitable for scenarios with limited professional maintenance capabilities.

Oil-immersed transformers have higher maintenance requirements, necessitating regular oil quality tests (analyzing parameters like dielectric losses, moisture content, and chromatography). Insulation oil needs replacement every 3-5 years, and along with that, inspections of sealing elements, breathing apparatus silicone, gas relays, and other accessories are vital. Maintenance demands are extensive, costs are high, and a professional maintenance team is required, making them suitable for enterprises or institutions with well-developed maintenance capabilities.

 

C. Environmental Adaptability
Dry-type transformers are compact and leak-free, exhibiting strong adaptability to environmental humidity and dust. They can be directly installed indoors, in basements, or in restricted spaces like equipment compartments, without necessitating separate machine rooms. Particularly suitable for indoor settings like urban commercial complexes, high-rise buildings, and data centers, they can reach protection levels up to IP54 and above, shielding against dust and moisture intrusion.

In contrast, oil-immersed transformers are voluminous and heavy, demanding separate machine rooms or installations on outdoor platforms or container substations. They require high installation foundation capabilities, are significantly impacted by environmental temperatures, and may require anti-freezing measures in low-temperature environments, with enhanced cooling in high-temperature settings. Additionally, insulation oil leaks may pollute soil and water sources, making them unsuitable for environments with high environmental protection standards.

 

D. Electrical Performance

1. Capacity and Voltage Levels: Dry-type transformers are more suitable for low to medium capacities (typically ≤35 kV, below 20 MVA), with a capacity ceiling often not exceeding 3150 kVA. They are ideal for decentralized load supply. Oil-immersed transformers can cater to super-large capacities and ultra-high voltages (hundreds of MVA, 500 kV and above), making them the preferred choice for large-capacity centralized loads and long-distance power transmission, such as in wind power and photovoltaic step-up stations and large substations.

2. Overload Capacity: Dry-type transformers have a stronger overload capacity, capable of withstanding short-term operation at 1.2-1.5 times the rated load. With a forced air cooling system, their overload performance can be further improved, making them suitable for scenarios with large fluctuations in power load. Oil-immersed transformers generally have a lower overload capacity, typically 1.1-1.3 times the rated load, but some large-capacity units can achieve higher overload capacity through optimized cooling systems.

3. Efficiency and Noise: Both types of transformers can achieve efficiencies of 98%-99%. However, oil-immersed transformers, due to the high heat dissipation efficiency of their insulating oil, can achieve efficiencies up to 99.5% in large-capacity models, slightly better than dry-type transformers. In terms of noise, oil-immersed transformers have a noise level of 50-60 dB, lower than dry-type transformers (55-65 dB), making them more suitable for noise-sensitive applications.

4. Lifespan and Recycling Value: Under proper maintenance, oil-immersed transformers can have a lifespan of 25-30 years, and their insulating oil is recyclable, resulting in high recycling value. Dry-type transformers have a lifespan of 20-25 years, limited by the aging of solid insulation materials, resulting in lower recycling value.

 

III. Scenario-Based Selection Guide (Precisely Matching Facility Needs)

The core of selection is "matching the actual needs of the facility." Based on the performance comparisons above and the core requirements of different scenarios, the following are clear selection recommendations, covering mainstream scenarios such as industrial, civil, and special locations:

(I) Scenarios Where Dry-Type Transformers are Preferred

1. Indoor High-Density Locations: Such as commercial complexes, office buildings, hotels, hospitals, schools, subway stations, airports, etc. The core requirement is fire safety. Dry-type transformers pose no fire hazard and emit no toxic gases. They can be directly installed in areas close to the load center, such as distribution rooms and basements, saving transmission losses and simplifying fire safety approval processes.

2. Space-Constrained Areas: Such as electrical shafts in high-rise buildings, equipment mezzanines, small distribution rooms, etc. Dry-type transformers have a compact structure and small footprint. They do not require a separate machine room and can be flexibly integrated into existing equipment layouts. A subway station case shows that embedding a dry-type transformer in a cable mezzanine can save 20 square meters of equipment space.

3. Scenarios with limited operation and maintenance capabilities: such as small and medium-sized enterprises, community power distribution, small office buildings, etc. Dry-type transformers are easy to maintain and do not require a professional oil maintenance team. They only need to be cleaned and inspected regularly, which can significantly reduce operation and maintenance costs and manpower input. After an industrial park was converted to dry-type transformers, the total cost of ownership was reduced by 35% over ten years.

4. Scenarios with high fire and explosion protection and environmental protection requirements: such as chemical explosion-proof areas, data center main server rooms, hospital operating rooms, etc. Dry-type transformers are flame-retardant, explosion-proof, and leak-free, causing no environmental pollution. They can adapt to clean, high-temperature environments and meet N+1 or 2N system redundancy requirements, ensuring continuous power supply to critical equipment.

(II) Scenarios where oil-immersed transformers are preferred

1. Outdoor large-capacity power supply scenarios: such as outdoor substations, industrial park distribution stations, wind power/photovoltaic booster stations, railway traction substations, etc. Oil-immersed transformers have strong weather resistance, can be installed outdoors, and can meet the requirements of large capacity and high voltage levels. In one wind power project, three 200MVA oil-immersed transformers supported the entire wind farm's grid connection and power generation.

2. Long-distance power transmission and centralized load scenarios: such as power plants, large industrial and mining enterprises (steel plants, chemical plants), rural power grids, etc. Oil-immersed transformers have high efficiency, long service life, and can withstand continuous and stable operation. They are suitable for large-capacity centralized load power supply, and the unit capacity manufacturing cost is relatively low, making them suitable for cost-sensitive projects.

3. Scenarios with professional operation and maintenance capabilities: such as professional power supply companies and large industrial enterprises, which have a complete operation and maintenance team and spare parts supply system, can meet the maintenance needs of oil-immersed transformers such as regular oil quality testing and oil replacement, and can give full play to their advantages of long life and high recycling value, thereby reducing the total life cycle cost.

(III) Selection Considerations for Special Scenarios

1. Data Centers: Dry-type transformers are mandatory. They must meet fire safety requirements and employ an N+1 redundancy configuration. Some high-end data centers may opt for 2N system redundancy to ensure continuous power supply to IT equipment and prevent data loss or business interruption due to transformer failure.

2. Chemical Plants: Dry-type transformers are preferred in explosion-proof areas. Outdoor oil-immersed transformers can be used in ordinary areas, but their corrosion resistance must be improved to withstand chemical corrosion. In harsh outdoor environments such as mines and ports, weather-resistant oil-immersed transformers are preferred, with enhanced sealing and heat dissipation design.

3. High-Rise Buildings: Dry-type transformers are required for basements, rooftops, and refuge floors. Rooftop installations must use waterproof transformers, and refuge floor installations must use fire-resistant transformers to ensure compliance with building fire safety codes and avoid safety hazards.

IV. Core Selection Principles and Summary

The core of choosing between dry-type and oil-immersed transformers lies in balancing four key factors: safety, cost, operation and maintenance, and scenario suitability. There's no need to pursue high-end or low-priced options; the optimal choice is one that best meets the actual needs of the facility. The core principles can be summarized in three points:

1. Scenario Priority: Indoor, densely populated areas with high fire safety requirements → Dry-type transformers; Outdoor, large-capacity, long-distance power transmission → Oil-immersed transformers. This is the core premise of selection and crucial for avoiding safety hazards and resource waste.

2. Cost Balance: Dry-type transformers have a 20%-40% higher initial investment than oil-immersed transformers of the same capacity, but lower operation and maintenance costs and smaller space requirements, making them suitable for scenarios with long-term operation and limited maintenance capabilities. Oil-immersed transformers have a lower initial investment, but higher operation and maintenance costs and larger footprint, making them suitable for large-capacity scenarios requiring specialized operation and maintenance. A comprehensive consideration of the entire lifecycle cost is necessary, rather than just focusing on the initial construction cost.

3. Compliance and Adaptation: Must comply with local power regulations, fire protection regulations and environmental protection requirements. For example, indoor installations must meet fire protection standards, and outdoor installations must meet waterproof, antifreeze and anti-corrosion requirements. Special locations (such as explosion-proof areas) require the selection of dedicated models. If necessary, consult professional design institutes or equipment suppliers to develop customized solutions.

 

In summary, dry-type transformers offer core advantages of "safety, convenience, and environmental friendliness," making them suitable for indoor, small-to-medium capacity, and low-maintenance scenarios. Oil-immersed transformers, on the other hand, offer core advantages of "large capacity, high efficiency, and low cost," making them suitable for outdoor, large-capacity scenarios requiring specialized operation and maintenance.

 

When selecting a transformer, facility managers should comprehensively evaluate their facility's installation environment, load characteristics, safety requirements, and maintenance capabilities to ensure long-term stable operation and provide a reliable power supply for the facility.

 

The key to improving the performance of drive motors in new energy vehicles lies in the continuous innovation of electrical silicon steel materials and coating technologies. As the core material of the motor stator core, the performance of low-iron-loss laminated silicon steel directly determines the motor's energy efficiency, power density, and range.

 

Thinning the steel sheet is one of the most effective technical approaches to reducing iron loss. Thinner silicon steel sheets can significantly reduce high-frequency eddy current losses and improve motor efficiency.

 

Low-iron-loss motor laminated silicon steel is indeed a key component in improving the energy efficiency of current motor technology. Through collaborative innovation in materials, processes, and design, it provides a solid foundation for the efficient, miniaturized, and low-noise operation of motors.

 

Low-iron-loss motor laminated silicon steel technology is directly driving energy efficiency upgrades in several key industries, such as new energy vehicle drive motors: this is currently the most cutting-edge area of  technology application. To achieve longer range and higher power density, new energy vehicle drive motors need to maintain low losses at high speeds. The use of ultra-thin silicon steel sheets has become a standard configuration for high-end motors.

 

In the future, technology will continue to evolve, moving towards thinner (e.g., 0.10mm and below), higher strength, and even integration with sensors to achieve intelligent status monitoring, providing continuous material support for the "dual carbon" goal.

 

Today I'm going to introduce a very important concept to all readers:

TOC about Dry-Type Transformer vs. Oil-Immersed Transformer.

1. WHAT IS TCO?

First let's clarify the Core Components of TCO (Not Just Purchase Price)

TCO = Initial Procurement Cost + Installation & Civil Construction Cost + Operating Loss Cost + Maintenance Cost + Compliance & Insurance Cost + Residual Value / Disposal Cost + Hidden Downtime Risk Cost

This is the key logic when comparing dry-type and oil-immersed transformers.
Many customers only look at the equipment price, ignoring long-term copper and iron losses, civil/fire protection costs, O&M, and fire risks.

 

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2. Key TCO Differences: Item-by-Item Comparison、

a. Initial Procurement Cost (CAPEX)

Oil-Immersed (Liquid-Filled):

For the same capacity and voltage level, lower unit price. Mature silicon steel and winding design gives strong economies of scale.

Dry-Type:
Epoxy resin cast or open-type structure, higher material and process cost, significantly higher upfront equipment price.

b. Installation, Civil Works & Supporting Infrastructure

Oil-Immersed:
Requires oil containment pit, firewalls, oil drainage pit, fire suppression system, independent transformer room or outdoor fencing.
→ High civil, fire protection, and anti-leakage investment, larger footprint.

Dry-Type:
No oil, no explosion protection, minimal fire protection requirements.
Can be installed indoors (distribution rooms, floors, basements) without oil pits or fire compartments.
→ Significantly lower civil costs and smaller footprint.

c. Operating Loss Cost (Largest TCO Component, Most Critical Long-Term)

No-load and load losses are similar, but dry-type has slightly poorer heat dissipation, leading to higher temperature rise under the same load.

Oil-filled units have better cooling and overload capability → slightly better long-term efficiency under full load.

TCO must be calculated based on 20–30 years of energy loss cost.
Differences are more pronounced under low-load or standby conditions.

d. Maintenance Cost (OPEX)

Oil-Immersed:
Requires regular oil testing, filtration, refilling, leak inspection, bushing cleaning, cooling fan maintenance.
→ Higher maintenance frequency and ongoing labor/material costs.

Dry-Type:
Almost maintenance-free. Only basic dust cleaning and insulation checks.
No oil handling or leakage risks → very low lifecycle O&M cost.

e. Safety, Compliance & Hidden Risk Costs

Oil-Immersed:
Uses flammable insulating oil → fire risk, leakage pollution, environmental compliance issues.
Restricted in high-rise buildings, malls, hospitals, and underground spaces.
High fire inspection cost and potentially huge downtime losses in case of fire.

Dry-Type:
Flame-retardant or non-flammable, no oil leakage, environmentally friendly.
Suitable for indoor, high-rise, underground, explosion-proof, and densely populated areas.
→ Near-zero hidden costs related to fire, environmental penalties, or downtime.

f. Lifespan, Residual Value & Disposal Cost

Oil-Immersed:
Lifespan 25–30 years. Transformer oil, core, and windings have high recycling value.
However, disposal requires professional oil treatment → environmental cost.

Dry-Type:
Lifespan 20–30 years. No oil disposal required.
Epoxy windings have slightly lower recycling value.

 

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3. Selection Conclusion 

When Oil-Immersed Has Better TCO?

Outdoor substations or industrial parks with ample space and no strict fire restrictions;

Large capacity, high-load, long-term operation → benefit from lower upfront cost and better cooling;

Sufficient land and acceptable civil/fire investment, less concern about maintenance labor.

When Dry-Type Has Better TCO?

High-rise buildings, malls, hospitals, subways, basements, and densely populated areas;

Explosion-proof, chemical plants, cleanrooms, environmentally strict facilities;

Avoid high civil/fire investment, prefer low maintenance and reduced fire/environmental risk;

Although higher upfront cost, over 20 years the savings in civil works, O&M, and risk far exceed the price difference → lower total TCO.

 

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4. Standard Approach to Building a TCO Report (Template Logic)

a. Set unified assumptions: same capacity, voltage, loss class, service life (20/30 years), and electricity price.

b. Break down costs: equipment cost, civil/fire cost, annual energy loss cost, annual maintenance, risk premium, residual value.

c. Apply discounted lifecycle cost calculation and determine payback period(How many years it takes to recover the higher dry-type cost through savings in energy, O&M, and civil works).

Transformer is an electrical device that uses the principle of electromagnetic induction to change alternating current voltage.

 

Its core structure consists of two sets of coils wound around a closed iron core. When alternating current is applied to the primary coil, an alternating magnetic field is generated in the iron core, which in turn induces an alternating voltage in the secondary coil. The voltage change depends on the turns ratio of the two coils. If the secondary coil has more turns than the primary coil, the output voltage will increase, which is called a step-up transformer; otherwise, it is a step-down transformer.

 

A transformer's main structure consists of three parts:

Core: Typically made of laminated silicon steel sheets, forming a closed magnetic circuit. Its function is to efficiently conduct and confine the magnetic field.

Primary Coil (Side): The winding connected to the input power supply.

Secondary Coil (Side): The winding that outputs the required voltage.

Key Characteristics and Parameters

• Rated Capacity: The maximum apparent output power that enables the transformer to operate safely for extended periods, measured in kilovolt-amperes (kVA).
• Rated Voltage: The primary and secondary operating voltages specified during design.
• Efficiency: The ratio of output power to input power. Modern large transformers can achieve efficiencies exceeding 99%, with losses primarily originating from copper and iron losses.
• Impedance voltage: An important technical parameter that affects the magnitude of short-circuit current and voltage regulation rate.

 

Simply put, transformers cleverly achieve the raising and lowering of AC voltage through the process of "electricity generating magnetism, and magnetism generating electricity," making them an indispensable basic component in modern power systems and almost all electronic equipment.

The CCS integrated busbar is mainly composed of signal acquisition components, plastic structural parts, copper and aluminum bars, etc. It is connected into a whole through processes such as hot pressing or riveting. It is applied in new energy vehicles and energy storage battery modules to achieve high-voltage series and parallel connection of battery cells, as well as temperature sampling and voltage sampling of battery cells. And it transmits information such as temperature and voltage to the BMS system through the information sampling component and connector, and is part of the BMS system.

As an important electrical connection component within the battery pack/ module, different cell assembly methods, battery pack calibration parameters, usage environments, as well as requirements for the internal space and weight of the battery pack, will all have different requirements for the sampling component, production process, and material selection of the CCS integrated busbar. Therefore, to meet the diverse demands of the application end, CCS products are constantly upgrading signal acquisition components, optimizing integration processes, etc., and have developed multiple technical routes, including multiple sampling schemes such as wiring harnesses, PCBS, FPCS, FFCS, FDCS, and FCC, as well as multiple integration solutions such as injection-molded brackets, splicing, PET hot-pressed films, and vacuum-formed isolation boards.

The current situation of technological development

To meet diverse application requirements, CCS products have developed multiple technical routes:

Sampling schemes: including wiring harnesses, PCBS, FPCS, FFCS, FDCS, FCC, etc

Integrated solutions: covering injection-molded brackets, splicing, PET hot-pressed films, vacuum-formed isolation boards, etc

 

Characteristics of mainstream integration processes:

Injection molded brackets + riveting process

Material: Flame-retardant PC+ABS or PA66

Advantages: High mechanical strength, good structural strength, and mature and stable technology

Limitations: A heavier product will affect the utilization rate of the internal space of the power battery and the improvement of its driving range. Large-sized forming is difficult, and the development of molds is challenging. The equipment cost is also high

Solution: Splicing isolation. Use several splicing support plates to replace the integrated injection molding brackets to reduce the difficulty of the injection molding process and equipment investment

 

Vacuum-formed isolation board + hot riveting process

Feature: Flame-retardant PC film vacuum forming

Advantages: Lightweight, low cost, high production efficiency, and high flexibility

Limitations: Relatively poor dimensional stability and relatively poor load-bearing capacity

 

Hot-pressed insulating film integration

Process: PET insulating film hot-pressing molding

Features: Thin, light and regular structure, high integration, higher stability, and capable of achieving automated assembly

Limitations: Large equipment investment and low production efficiency

 

Flat plate structure + riveting

Application: Mainly applicable to stationary energy storage

Feature: Prominent cost advantage

Limitation: Relatively weak seismic performance

Overall, different integration processes of CCS integrated busbars each have their own advantages, and the most suitable solution should be selected based on specific application scenarios. For instance, in the field of new energy vehicles, hot-pressing or injection molding solutions can be given priority, while for fixed energy storage, flat plate riveting solutions can be selected.

 

 

Have you ever felt confused by the intricate wires inside your car when inspecting or repairing it?

The color, cross-sectional area and number of wires all have their specific meanings and standards, which are crucial for ensuring the safe operation of the vehicle's electrical system.

 

Wire color coding

Wire color coding is a standardized method used to distinguish electrical systems with different functions. This coding system helps avoid incorrect connections during installation, maintenance or repair, thereby improving work efficiency and reducing electrical faults.

 

Monochromatic wires and bicolor wires

The insulation layer color of wires is divided into two types: single color and double color.

Monochromatic wire: The insulation layer color is a single color, represented by an English letter. For example, red is represented by "R".

Two-color wire: The insulation layer color is composed of two colors, the main color and the secondary color, with a ratio of the main color to the secondary color of 3:1, represented by two English letters. The first letter represents the primary color and the second letter represents the secondary color. For example, the red and white bicolor wires are represented by "RW".

 

Color code table

The following are some common wire colors and their codes:

Red (R) - RD

White (W) -WH

Black (B) - Bk

Green (G) -Gn

Yellow (Y) -YE

Brown (N) -Br

Blue (U) -Bl

Gray (S) -Gr

Purple (V) - VI

Orange (O) - Or

Pink (P)

 

Selection of cross-sectional area of wires

The cross-sectional area of the wires selected varies depending on the power of the electrical appliances used. The following are some common circuits and their recommended cross-sectional areas:

Taillights, roof lights, indicator lights, instrument lights, license plate lights, electronic clock: 0.5mm ²

Turn signals, brake lights, distributors, etc. : 0.8mm ²

Headlamp low beam, electric horn (below 3A) : 1.0mm ²

Headlamp high beam, electric horn (3A or above) : 1.5mm ²

Other circuits above 5A: 1.5-4.0 mm²

Electric heating plug: 4-6 mm²

Power cord: 4-25 mm²

Starting circuit: 16-95 mm²

 

Selection of wire types

Depending on the installation location of the electrical appliances, the types of wires selected also vary. For example:

High-temperature resistant wires should be used in high-temperature areas (such as engine Windows, etc.).

Ordinary wires are used in general areas.

 

Wire numbering standard

The numbering standard of wires is helpful for identifying the type and specification of wires.

The following are some common wire numbers and their usage standards:

QVR, QVR105: Comply with the JB/T 8139-1999 standard

AVSS, AVS, AVSS105: Comply with the JASO D 611 standard

AV: Complies with the KS C 3311 (JIS C 3406) standard

AEX: Complies with the JASO D 608 standard

QB-B: Complies with the QC/ T730-2005 standard

SHE-K: Shielded wire

 

Now, you should have a deeper understanding of the color coding, cross-sectional area selection and wire numbering standards in automotive wire systems. These standards are crucial for ensuring the safe operation of the vehicle's electrical system. By following these standards, the safety, reliability and maintenance efficiency of automobiles can be enhanced.

It is very important for car manufacturers, maintenance technicians and car owners to understand and comply with these coding standards. This not only helps protect the vehicle, but also contributes to the safety of the driver and passengers. Next time when you face the wires in your car, you will be able to identify and handle them with more confidence.

What is a shielded wire?

Definition: A wire with a conductor wrapped around the outside is called a shielded wire. The wrapped conductor is called a shielding layer, which is generally a braided copper mesh or copper foil (aluminum). The shielding layer needs to be grounded, and external interference signals can be conducted into the earth through this layer.

 

Function: To prevent interference signals from entering the inner layer, avoid conductor interference, and reduce the loss of the transmitted signal at the same time. Structure: (Common) Insulation layer + shielding layer + wire (advanced)

Insulation layer + shielding layer + signal conductor + shielding layer grounding conductor

Note: When choosing shielded wires, the shielding layer grounding wire. The insulating layer of the shielding layer grounding wire has a conductive function and can conduct electricity with the shielding layer (with a certain resistance).

 

 

The principle of shielded cables

The shielded cabling system originated in Europe. It is a common unshielded cabling system with a metal shielding layer added outside. By taking advantage of the reflection, absorption and skin effect of the metal shielding layer, it achieves the function of preventing electromagnetic interference and electromagnetic radiation. The shielded system comprehensively utilizes the balance principle of twisted-pair cables and the shielding effect of the shielding layer, thus having very good electromagnetic compatibility (EMC) characteristics.

 

The balance characteristics of U/UTP(unshielded) cables do not only depend on the quality of the components themselves (such as twisted pairs), but are also affected by the surrounding environment. Because the metal around U/UTP (unshielded), concealed "ground", pulling, bending and other conditions during construction can all disrupt its balance characteristics, thereby reducing the EMC performance. Therefore, to achieve a lasting and unchanging balance characteristic, there is only one solution: to ground all the core wires by adding an extra layer of aluminum foil. Aluminum foil adds protection to the fragile twisted-pair core wire while artificially creating a balanced environment for U/UTP (unshielded) cables. Thus, what we now call shielded cables are formed.

 

The shielding principle of shielded cables is different from the balance cancellation principle of twisted-pair cables. Shielded cables add one or two more layers of aluminum foil outside the four pairs of twisted-pair cables. They utilize the reflection, absorption of electromagnetic waves by metals and the skin effect principle (the so-called skin effect refers to the distribution of current across the cross-section of a conductor tending to the surface of the conductor as the frequency increases. The higher the frequency, the smaller the skin depth, that is, the higher the frequency, the deeper the skin The weaker the penetrating power of electromagnetic waves, the more effectively it can prevent external electromagnetic interference from entering the cable, and at the same time, it can also prevent internal signals from radiating out and interfering with the operation of other equipment.

Experiments show that electromagnetic waves with frequencies exceeding 5MHz can only pass through aluminum foil 38μm thick. If the thickness of the shielding layer exceeds 38μm, the frequency of electromagnetic interference that can penetrate the shielding layer and enter the interior of the cable will mainly be below 5MHz. For low-frequency interference below 5MHz, the balance principle of twisted-pair cables can be effectively applied to cancel it out.

 

According to the earliest definition of wiring, it is divided into two types: unshielded cables -UTP and shielded cables -STP. Later, with the development of technology and the different processes of various manufacturers, many different types of shielding have emerged

1. F/UTP Foil Screened Cable single-layer foil shielding structure

2. Foil and Braid Screened Cable foil and copper braided mesh double-layer shielding structure

a)SF/UTP aluminum foil and copper woven mesh are simultaneously wrapped around the outer layers of the four pairs of wires

b)S/FTP (PIMF) wire pairs: Single Pair aluminum Foil shielding plus copper braided mesh wrapped around the outer layer of the four pairs of wires. PIMF =Pair in Metal Foil.

The resistance of shielded cables to external interference is mainly reflected in the fact that the integrity of signal transmission can be guaranteed to a certain extent through the shielding system. The shielded wiring system can prevent the transmitted data from being affected by external electromagnetic interference and radio frequency interference. Electromagnetic interference (EMI) is mainly low-frequency interference. Motors, fluorescent lamps and power cables are common sources of EMI. Radio Frequency Interference (RFI) is high-frequency interference, mainly wireless frequency interference, including radio, television broadcasting, radar and other wireless communications.

For resisting electromagnetic interference, braided layer shielding is the most effective choice, that is, metal mesh shielding, because it has a relatively low critical resistance. As for radio frequency interference, metal foil shielding is the most effective, because the gaps created by metal mesh shielding allow high-frequency signals to enter and exit freely. For interference fields with mixed high and low frequencies, a combined shielding method of metal foil layer and metal mesh should be adopted, that is, a double-layer shielded cable in the form of S/FTP. This enables the metal mesh shielding to be suitable for low-frequency range interference and the metal foil shielding to be suitable for high-frequency range interference.

 

The single-layer thickness of the aluminum foil shielding layer in the shielded cables of IBM ACS reaches 50-62μm, achieving a more complete shielding effect. At the same time, as only a single layer of shielding is adopted, it will be simpler for construction, easier to install, less likely to cause man-made damage during the construction process, and the thickness of the aluminum sheet can withstand greater destructive force. Thus, it can provide users with higher-quality transmission performance.

The rapid development of new energy vehicles is reshaping the automotive industry chain pattern, and the wiring harness system, as the "nervous system" of vehicles, has also undergone profound changes in its technical demands and market structure. From high voltage, intelligence to lightweighting, the wire harness industry is undergoing an all-round upgrade from material innovation to manufacturing models. This article will analyze the core impact of new energy vehicles on the demand for wiring harnesses from three dimensions: technological evolution, market landscape, and future trends.

 

 

The revolution of high-voltage drive technology

The popularization of 800V high-voltage platforms

The trend of high voltage in new energy vehicles is significant. The popularization of 800V platforms (such as Porsche Taycan and XPeng G9) has driven the voltage resistance level of wiring harnesses to increase from the traditional 600V to over 1500V. High-voltage wiring harnesses need to adopt new technologies such as silicone insulation and three-layer shielding structure to suppress partial discharge and electromagnetic interference (EMI), while meeting the ISO 26262 functional safety standard.

Material breakthrough: Cross-linked polyethylene (XLPE) and ceramic nanocomposites have been widely applied, and the temperature resistance grade has been raised to 200℃.

Liquid cooling technology: The liquid-cooled charging gun wiring harness of the Porsche Taycan can achieve a continuous current of 500A, with temperature rise controlled within 30K.

 

The market has exploded

In 2022, the market size of high-voltage wiring harnesses in China was 14.14 billion yuan. It is expected to reach 23.8 billion yuan by 2025, with a compound annual growth rate of 28%. Globally, the market size of high-voltage wiring harnesses is expected to exceed 18 billion US dollars by 2025, with China accounting for 45%.

 

 

Intelligence and architecture Reconfiguration

Transformation of electronic and electrical architecture

The application of the Zonal Architecture significantly reduces the length of the wiring harness (for example, the wiring harness of Tesla Cybertruck is shortened to 100 meters), but the problem of cross-domain signal synchronization needs to be solved. In-vehicle Ethernet (with a bandwidth of 10Gbps) is gradually replacing CAN bus and becoming the core of intelligent driving data transmission.

 

The demand for sensors has soared: The number of sensors in L3+ autonomous driving models has exceeded 30, and the demand for dedicated optical fiber harnesses for lidar has increased by 62% annually.

 

 

Lightweighting and cost challenges

Material substitution and process innovation

Aluminum wire substitution: The electrical conductivity of aluminum wire reaches 97% of that of copper, its weight is reduced by 30%, and its cost is cut by 40%. By 2025, its application proportion is expected to reach 22%.

Carbon fiber composite material: The weight of the sheath is reduced by 60%, helping to reduce the overall vehicle weight by 10% to 15%.

 

Cost pressure and automation upgrade

Raw material costs account for 65% to 80% of the total cost of wiring harnesses, among which copper materials have the highest proportion. By means of automated production (crimping accuracy ±0.1mm) and digital twin technology, the automation rate of domestic wire harness factories will reach 75% by 2025, and labor costs will be reduced by 40%.

 

 

Reconstruction of the supply chain ecosystem

The acceleration of domestic substitution

Foreign manufacturers (such as Yazaki and Aptiv) have long held over 70% of the market share. However, domestic enterprises like Huguang Co., Ltd. and Kabeiyi have increased their market share from 3% to 28% through technological breakthroughs (such as high-voltage wire harnesses withstand 1000V) and customer expansion (entering the supply chains of Tesla and BYD).

 

 

Standardization and modularization

Byd e-Platform 3.0 has reduced the number of connector types from 120 to 30, increasing assembly efficiency by 25%. Aptiv's Intelligent Automotive Architecture (SVA) drives wiring harness suppliers to transform towards modular system integration.

 

 

Future trends: Intelligence and sustainability

Intelligent wiring harness system

Embed fiber Bragg grating sensors to monitor temperature and strain in real time; Self-healing material technology can extend the lifespan of wiring harnesses by 30%.

 

Green manufacturing

The EU's "New Battery Regulation" requires that the recycling rate of wiring harnesses exceed 95%, and the carbon footprint of bio-based materials (such as BASF Ultramid® Bio) be reduced by 60%, which has been applied to the SAIC IM Motors L7.

 

Wireless exploration

The BMW iX reduces the number of door wiring harnesses by 12 through UWB technology, but the backbone network still relies on wired transmission. It is expected that by 2025, the proportion of the "wired + wireless" hybrid architecture will exceed 80%.

 

 

The explosive growth of new energy vehicles has driven the wiring harness industry to leap from traditional manufacturing to a high-tech intensive industry. Future competition will focus on materials science (such as superconducting technology), intelligent manufacturing (such as AI quality inspection), and ecological collaboration capabilities. Domestic manufacturers are gradually breaking the monopoly of foreign capital through technological breakthroughs and supply chain integration. This transformation is not only an iteration of technology, but also a crucial battle for the redistribution of value in the global automotive supply chain.

Introduction  

 

In the world of electronics and electrical systems, wire harness and cable assembly manufacturing plays a crucial role in ensuring reliable connectivity and efficient power distribution. Whether in automotive, aerospace, industrial machinery, or consumer electronics, these components are essential for transmitting signals and power safely.  

 

This blog explores what is a cable assembly, the differences between wire harness and cable assembly, the benefits of custom molded cable assemblies, and how to choose the right cable assembly manufacturers for your needs.  

 

What is a Cable Assembly?  

A cable assembly is a group of wires or cables arranged into a single unit for transmitting electrical power or signals. These assemblies are often bound together with connectors, sleeves, or protective coverings to ensure durability and ease of installation.  

Unlike a simple bundle of wires, a cable harness assembly is designed for specific applications, with precise lengths, shielding, and connectors to meet industry standards.  

 

Key Features of Cable Assemblies:  

- Protection: Shielding against EMI/RFI interference, moisture, and abrasion.  

- Organization:Neat bundling of multiple wires for easier installation.  

- Customization:Tailored lengths, colors, and connectors for specific applications.  

 

Wire Harness vs. Cable Assembly  

While the terms wire harness and cable assembly are sometimes used interchangeably, they serve different purposes:  

Wire Harness:  

- Typically consists of multiple wires bound together with sleeves or tape.  

- Used for internal electrical connections within a device or machine.  

- Less rugged than cable assemblies, often used in controlled environments.  

 

Cable Assembly:  

- More robust, with additional shielding and protective jackets.  

- Designed for harsh environments (e.g., automotive, aerospace, industrial).  

- Often includes molded connectors for secure connections.  

For applications requiring high durability, a cable harness assembly with reinforced insulation and strain relief is preferred.  

 

Applications of Wire Harness & Cable Assemblies  

These components are used across various industries:  

- Automotive: Engine control systems, infotainment wiring.  

- Aerospace: Avionics, flight control systems.  

- Medical Equipment: Patient monitoring devices, imaging systems.  

- Industrial Machinery: Robotics, automation systems.  

- Consumer Electronics: Appliances, computers, and smartphones.  

 

Benefits of Custom Molded Cable Assemblies  

For specialized applications, custom molded cable assemblies offer several advantages:  

1. Precision Fit: Designed to exact specifications, ensuring compatibility.  

2. Enhanced Durability: Overmolded connectors provide strain relief and protection.  

3. Improved Performance: Reduced signal interference and better electrical conductivity.  

4. Cost Efficiency: Minimizes the need for additional adapters or modifications.  

Leading cable assembly manufacturers provide tailored solutions for industries requiring high-performance wiring systems.  

 

Choosing the Right Cable Assembly Manufacturers  

When selecting a supplier for wire harness and cable assembly, consider the following:  

 

- Experience & Expertise: Look for manufacturers with industry-specific knowledge.  

- Certifications: ISO, UL, and IPC standards ensure quality compliance.  

- Customization Capabilities: Ability to produce custom molded cable assemblies.  

- Testing & Quality Control: Ensures reliability and performance.  

 

Conclusion 

Wire harness and cable assembly manufacturing is a critical aspect of modern electronics, ensuring efficient and reliable connectivity. Whether you need a standard cable harness assembly or a specializedcustom molded cable assembly, choosing the right cable assembly manufacturers is key to achieving optimal performance.  

 

By understanding what is a cable assembly and its applications, businesses can make informed decisions for their electrical connectivity needs. 

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