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The UL power cord waterproof test method mainly relies on UL-related standards. The following are common test methods:

Spray test

During the test, install the power cord at the designated position to simulate the actual usage state. The test equipment is used as the water outlet nozzle to conduct rain tests from top to bottom or water spraying tests from bottom to top on the power cord in accordance with the standard requirements.

During the testing process, it is necessary to control the sequence and timing of water on and off. For instance, first turn off the water source and light up the lamps for one hour, then turn on the water source and turn off the lamps for half an hour to observe the performance of the power cord in a humid environment.

After the test, it is necessary to check whether the power cord is affected by water and cannot work normally, or whether there are other risks and hazards. At the same time, it is necessary to ensure that water does not come into contact with charged objects. Unless the line type can withstand immersion, water droplets should not condense into small pools.

Immersion test

For power cords that require a higher waterproof rating, a water immersion test may be conducted. When testing, fully immerse the power cord in water for a certain period of time (such as half an hour), and then take it out to check if its performance is affected.

Immersion tests are typically used to evaluate the waterproof performance of power cords in extremely humid environments, ensuring their electrical safety during actual use.

Air tightness test

In addition to the traditional water immersion method, the air tightness testing method can also be used to conduct a waterproof test on the power cord. This method assesses the waterproof performance of power cords by testing their airtightness, featuring higher precision and efficiency.

During the air tightness test, the power cord is placed in a sealed container, and then gas at a certain pressure is filled into the container. The waterproof performance of the power cord is determined to be qualified by detecting the amount of gas leakage.

The key points of fire protection design for UL power cords mainly include the following aspects:

Material selection

Insulating materials should have good flame retardant performance and usually need to meet the V-0, V-1 or V-2 grades in UL 94 standards to ensure rapid self-extinguishing under the action of flames.

The sheath material also needs to have flame-retardant properties and be less likely to decompose or release toxic gases in high-temperature environments, in order to reduce the smoke and toxicity hazards in fires.

Flame retardant grade matching

Select the appropriate flame retardant grade based on the usage scenario. For instance, the pressurized CMP cable is suitable for ventilation ducts, the main line CMR cable is suitable for building main lines, and the commercial grade CM cable is suitable for horizontal wiring.

Cables of different grades must meet the corresponding fire protection test standards. Parameters such as flame spread distance and self-extinguishing time must comply with UL specification requirements.

Structural design

It adopts a multi-layer structure design, enhancing the overall fire resistance performance through the superposition of insulating layers, flame-retardant layers and sheath layers.

Add fire barriers or insulation layers to restrict the spread of flames and heat into the cable interior or other areas.

Testing and Certification

Fire protection design must pass strict tests in UL laboratories, including flame spread tests, smoke density tests and toxic gas release tests.

The surface of the cable should be printed with UL identification letters, fire resistance ratings and approval numbers to ensure compliance with safety standards and facilitate traceability.

Application scenario adaptation

For places with high fire protection requirements such as high-rise buildings and data centers, flame-retardant, low smoke and halogen-free cables should be selected to reduce the release of toxic gases in case of fire.

Avoid using halogen-containing PVC pipes or conduits in areas where flame-retardant cables are laid to prevent the generation of additional toxic smoke during high-temperature combustion.

Installation and laying specifications

The cable laying method must comply with fire protection requirements. For instance, fire-fighting power distribution lines should use fire-resistant cable trays or metal trays with a fire-resistant protective layer coated on the outer wall.

Avoid mixing flame-retardant and non-flame-retardant cables. Cables of the same flame-retardant grade should be used in the same channel, and sufficient margin should be reserved to cope with possible future load increases.

Safety design redundancy

Cable design should take thermal stability into account to ensure that it can still function normally under extreme temperature changes and avoid fires caused by overheating.

Structurally, it should possess mechanical strength and pass impact and vibration tests to ensure structural integrity and electrical safety under external forces.

The determination of the flame retardant grade of UL power cords mainly relies on the relevant test methods in UL standards. The following is a detailed analysis of its determination methods:

First, the main flame retardant grades and their determination criteria

VW-1 grade

Test method: Vertical burning test. Place the wire vertically and use a special fire source to light one part of the wire. The fire supply should last for 15 seconds. After stopping the fire supply, observe the burning situation of the wire.

The criterion for judgment: The wire should continue to burn for no more than 60 seconds, and the dripping substances from the burning should not ignite the cotton bedding placed below. The above operation needs to be repeated five times (at the same ignition position) before it can be determined that the test is qualified. In addition, the burning mark (such as kraft paper) cannot be carbonized by more than 25%.

FT1 grade

Test method: Similar to VW-1, it is also a vertical burning test, but there are no strict requirements for dripping substances.

Judgment criteria: Mainly focus on the self-extinguishing ability of the wire and the degree of carbonization of the combustion mark.

FT2 grade

Test method: Horizontal burning test. Place the wire horizontally and light one part of the wire with a special fire source to observe the burning situation of the wire.

The criterion for judgment: The fire supply should last for a certain period of time (such as 15 seconds). After the fire supply is stopped, if the extended burning length of the wire does not exceed a certain distance (such as 100mm), the test is judged as qualified. The FT2 level is relatively easy to pass among these levels and has the lowest level.

Second, the differences from other standards

UL94 standard: This standard is mainly used to assess the flame retardant performance of plastic materials and is different from the UL flame retardant grade for power cords (for wires and cables). The UL94 standard includes multiple grades, such as HB, V-0, V-1, V-2, etc. These grades are evaluated through different combustion test methods.

The difference between the test objects and methods: UL94 examines the materials used for wires and requires the formulation of standard samples with separate test materials, without marking on the wires. The flame retardant grades of UL power cords (such as VW-1, FT1) assess the wires themselves. After passing the test, the corresponding grades can be marked on the wires.

The selection of the rated voltage for UL power cords needs to comprehensively consider the characteristics of insulating materials, the usage environment, and the provisions of UL standards. The following is a specific analysis:

The withstand voltage capacity of insulating materials

The withstand voltage capacity of insulating materials is a key factor in determining the rated voltage. Take polyvinyl chloride (PVC) insulating material as an example, its dielectric strength has a certain range. In the experiment, by gradually increasing the voltage until the insulating material is broken down, this breakdown voltage value is an important reference for determining the rated voltage. Usually, a certain coefficient is reserved on the basis of the breakdown voltage. For instance, if the breakdown voltage of a certain insulating material is 10kV/cm, considering environmental factors and aging factors in actual use, the electric field strength corresponding to the rated voltage may be set at 3-5kV/cm.

Environmental impact of use

Different usage environments have a significant impact on the rated voltage. In a dry and clean indoor environment, the performance of insulating materials can be well exerted, and the rated voltage can be relatively high. However, in a humid environment with corrosive gases, the insulation performance will decline. For instance, in places like chemical plants, due to the presence of chemical corrosive substances, insulating materials will be eroded and their withstand voltage capacity will be reduced. Therefore, the rated voltage of UL power cords used in such environments will be correspondingly reduced.

The UL standard stipulates

UL certification follows a series of standards, which stipulate the rated voltages of different types of wires in various application scenarios. For instance, for wires used in general residential electrical systems, according to UL relevant standards, their rated voltage may be specified as 600V. This is determined after comprehensively considering the possible voltage peaks within the residence (such as instantaneous high voltage situations like motor startup) and the margin. Some internal connection wires of electronic and electrical equipment, such as UL1007 electronic wires, have a standard rated voltage of 300V and are suitable for use in low-voltage electrical equipment. The UL1015 electronic wire has a rated voltage of 600V and is suitable for scenarios with different electrical performance requirements.

The detachable component design of UL power cords is typically used to enhance the flexibility of product usage and the convenience of maintenance. The following is an analysis from three aspects: design features, structural composition, and functional advantages:

Design features

The detachable component design enables users to replace or upgrade power cord assemblies, such as plugs and connectors, according to actual needs. This design enables the power cord to adapt to the electrical standards of different countries or regions, as well as the interface requirements of various devices. Meanwhile, the detachable design also facilitates the maintenance and replacement of power cords, reducing maintenance costs.

Structural composition

Detachable components usually include plugs, connectors and possible adapter parts. The plug part may adopt standardized designs, such as two-hole or three-hole plugs, to adapt to different socket types. The connector part may adopt a quick-plug design, facilitating users to quickly connect or disconnect the power cord. The adapter component is used to achieve the conversion between different interfaces, such as converting the power cord from one plug type to another.

Functional advantage

Flexibility: Users can replace the plug or connector as needed to adapt to different usage environments and equipment requirements.

Maintenance convenience: When the power cord malfunctions, users can replace only the damaged parts without having to replace the entire power cord, thereby reducing maintenance costs.

Safety: The design of detachable components usually adheres to strict safety standards, such as UL certification, to ensure safety during use. For instance, some designs employ magnetic interfaces or elastic snap-on components. When the external force exceeds a certain threshold, the components will automatically disconnect, effectively protecting electronic devices and preventing personal injury.

The integrated molding structure of UL power cords usually involves the integrated design of key components such as power cord conductors, insulation layers, and sheaths. The following is an analysis from three aspects: structural design, material application, and performance advantages

Structural design characteristics

The integrated molding structure integrates the power cord conductor, insulation layer and sheath and other components into a unified whole through a special process, forming a compact cable structure. This design eliminates the split assembly method of each component in traditional cables and adopts continuous extrusion or injection molding processes to achieve seamless combination between materials. For instance, the outer layer of the conductor is directly wrapped with insulating material, and then an integrated structure is formed with the outer sheath through co-extrusion process, effectively reducing the interlayer gap.

Advantages of material application

The insulating layer and sheath materials are mostly high-molecular polymers such as thermoplastic elastomers (TPE) or polyvinyl chloride (PVC), and the properties of flame retardancy, weather resistance and oil resistance are achieved through formula optimization. Some high-end products use cross-linked polyethylene (XLPE) insulating materials, and their temperature resistance grade can reach above 105℃. Material selection needs to take into account both electrical performance and mechanical strength. For example, sheath materials with high tensile strength are adopted to enhance the bending resistance of the cable, and at the same time, flame retardants are added to meet the UL VW-1 flame retardant standard.

Analysis of Performance Advantages

The integrated molding structure significantly enhances the mechanical protection capacity of the cable. Its tensile strength is increased by more than 30% compared with the traditional structure, and the pass rate of the withstand voltage test is raised to 99.5%. The sealing performance optimization enables the waterproof grade to reach the IP67 standard, and it can withstand immersion in a water depth of 1 meter for 30 minutes. In terms of production efficiency, the continuous extrusion process shortens the single-line production cycle by 40% and increases the material utilization rate to 95%. In practical applications, the service life of this structure of cable is extended to 2 to 3 times that of traditional cables in high-frequency bending scenarios such as industrial robots and medical equipment.

The insulation layer color of UL power cords has specific meanings. These color markings help correctly distinguish the phase wire, neutral wire, protective ground wire, etc. in the wires, thereby preventing incorrect operations. The following are the common insulation layer colors of UL power cords and their meanings:

Black:

It is usually used for internal wiring of devices and equipment, and is also commonly found in the power lines of electrical equipment. It can carry a large current and ensure the stable operation of the equipment.

Brown

Used for the positive terminal of a DC circuit.

Red:

In a three-phase circuit, red is often used to represent phase C.

It is also widely used in control circuits, such as in the control loops of automated equipment and distribution boxes, for transmitting control signals.

Yellow:

In A three-phase circuit, yellow is often used to represent phase A.

It can also be used as the base of semiconductor transistors, the control electrode of thyristors and bidirectional thyristors.

Green:

In a three-phase circuit, green is often used to represent phase B.

Green or yellow-green bicolored wires are a prominent sign of grounding, used to direct leakage current into the ground to prevent the risk of electric shock to people.

Blue:

The negative pole used in a DC circuit.

In alternating current circuits, blue is also often used to represent the neutral line or the zero line, playing a role in balancing voltage and ensuring the normal return of current.

Light blue

It is specifically used to represent the neutral line or neutral line of a three-phase circuit, as well as the grounding neutral line of a DC circuit.

White or grey

It is generally used as a neutral line and plays a role in balancing voltage and ensuring the normal return of current in AC circuits.

It can also be used for braided tapes or insulating layers to distinguish grounded (neutral) conductors.

Yellow and green bicolor

Grounding wires specifically used for safety purposes, with each color approximately 15 to 100 millimeters wide, are alternately attached.

Other colors:

Such as orange, purple, gray, greenish blue, rose red, etc., may also be used in specific circumstances or according to specific standards, but they are usually not mainstream colors.

The application scope of UL power cord rubber insulation is extensive, mainly reflected in the following aspects:

High-temperature environment: Rubber insulating materials have excellent heat resistance and can withstand relatively high working temperatures. For instance, silicone rubber insulated wires can be used within a temperature range of -60℃ to 200℃ and are suitable for the connection between high-temperature electrical equipment in industrial fields such as power generation, metallurgy, and chemical engineering.

Low-temperature environment: Rubber insulating materials also have excellent cold resistance. They can maintain softness and elasticity in low-temperature environments and are not prone to hardening or becoming brittle. This makes rubber-insulated power cords suitable for cold regions or electrical equipment that requires low-temperature operation.

Oil-resistant and corrosion-resistant environment: Rubber insulating materials have excellent oil resistance, acid and alkali resistance, and corrosion resistance, and can be used for a long time in harsh environments such as oil stains and chemical corrosion. Therefore, rubber insulated power cords are often used in the automotive industry, mechanical equipment, petrochemicals and other fields.

In situations where flexible insulation is required: Rubber insulating materials have excellent elasticity and wear resistance, and can withstand mechanical stress when bent multiple times with small bending radii. This makes rubber insulated power cords suitable for situations where frequent movement or bending is required, such as power supply lines for movable devices, power tools, electric vehicles, etc.

Household appliances and electronic devices: Rubber insulated power cords are also widely used in the internal connections of household appliances, lighting fixtures, electronic devices, etc. Its excellent insulation performance and mechanical properties can ensure the safe operation of electrical equipment.

The performance analysis of PVC insulation in UL power cords is as follows:

Flame retardant performance: PVC insulating materials have excellent flame retardant properties. They have a high flame retardant grade and can easily meet various standard requirements. Therefore, they are widely used in the fire protection field and are one of the most commonly used insulating materials in flame-retardant and fire-resistant wires and cables.

Temperature resistance performance: The maximum continuous working temperature of common PVC insulating materials is generally 70℃, while by adding heat-resistant plasticizers, its working temperature can be raised to 90℃. However, PVC is prone to accelerated aging at high temperatures and becomes hard and brittle in low-temperature environments (below -15℃), making it unsuitable for use in cold conditions.

Mechanical and processing performance: PVC insulating materials have mature manufacturing technology and excellent processing performance, with low cost. Moreover, they can effectively control the color difference, matte finish, printing, processing efficiency, softness and hardness, conductor adhesion, as well as mechanical, physical and electrical properties of the wire surface.

Chemical stability: PVC insulating materials have excellent resistance to acids, alkalis, and chemical corrosion, but they perform poorly in terms of resistance to heat-resistant oils and organic solvents. They are prone to damage and cracking in specific environments.

Environmental and safety impact: PVC materials contain chlorine. When burned, they release a large amount of thick smoke and toxic gases (such as HCl), which pose a threat to the environment and human health. With the development of low smoke zero halogen materials, gradually replacing PVC has become a trend in the cable industry.

Application fields: Due to its low cost and excellent processing performance, PVC insulating materials are widely used in low-voltage distribution lines of household appliances, instruments and meters, lighting, network communication, etc., especially as basic insulating and sheathed materials in terminal circuits.

The UL power cord insulation thickness standard varies by specific model and application scenario. The following are some general standards and regulations:

UL758 standard

This standard has clear requirements for the minimum thickness of the insulation layer, usually stipulating that the minimum thickness of the insulation should not be less than 90% of the average thickness. This means that during the production process, the thickness of the insulation layer needs to be kept relatively uniform to ensure its electrical and mechanical properties.

For power cords of different specifications, the minimum thickness and average thickness of the insulation layer will vary. For example, for some models of UL power cords, the minimum thickness of the insulation layer may be required to be no less than 0.33 millimeters, while the average thickness may be higher.

The thickness of the insulation layer of the specific model:

Take UL1007 electronic wire as an example. Its insulation layer adopts extruded PVC plastic insulation layer, and the minimum average thickness shall not be less than 0.38 millimeters, and the minimum thickness shall not be less than 0.33 millimeters. This regulation ensures that the insulation layer can provide sufficient electrical isolation while maintaining a certain mechanical strength.

For other models of UL power cords, such as UL2464, etc., there may also be specific regulations on the average thickness of the insulation layer and sheath. For instance, the sheath thickness of some multi-core wires may reach 0.8 millimeters or even higher.

Testing and Judgment

During the production process, the thickness of the insulation layer needs to be strictly tested to ensure that it meets the requirements of the UL standard. The testing methods usually include precise measurement using measuring tools such as micrometers.

The determination rules are usually based on the actual requirements in the Style Page (or Facing Page). If a certain model has specified minimum thickness and average thickness, these regulations shall prevail. If only the minimum or maximum thickness is specified, the corresponding requirements must be met, and at the same time, the requirements of other standards such as CSA for the ratio of minimum thickness to average thickness should also be taken into consideration.