The Reasons and Functions for selected the Solenoid Twisted Wires

Part 1.  The Reasons for Solenoid selected the Twisted Wires 

1.1. Mechanical performance requirements

During the operation of the solenoid, its power cord may be subjected to various external forces. For example, in some automated equipment, the power cord of the DC solenoid will bend and stretch continuously with the moving parts of the equipment. If it is a single power cord, it is easy to be damaged, such as breaking, under these mechanical stresses. The use of stranded wire can effectively improve the flexibility and tensile strength of the power cord. Stranded wire is made of multiple thin wires twisted together. When bending, each thin wire can slide and adjust its position to share the stress generated by bending; when stretching, the combined force of multiple thin wires can withstand greater tension, making the power cord more durable.

1.2. Electromagnetic compatibility considerations

The electromagnet itself is a actuator device that works on the principle of electromagnetic induction and generates a strong magnetic field when working. At the same time, it may be interfered by external electromagnetic fields. As a part of transmitting electrical energy, the performance of the power cord will affect the electromagnetic compatibility of the entire system. A single power cord will generate a relatively concentrated magnetic field when transmitting current, which is easy to interfere with surrounding electronic equipment, and it is also easily interfered by external magnetic fields. The structure of the twisted wire can make the magnetic field generated by the current cancel each other out. Since the direction of the current in the twisted wire changes alternately, the magnetic field also cancels each other out, which can effectively reduce electromagnetic interference. At the same time, the external electromagnetic field will generate induced current in the twisted wire, and these induced currents cancel each other out between different twisted wires, thereby reducing the impact on the power line transmission signal.

1.3. Convenience of production process

 In production process, thinner single wires are easier to process. Twisting multiple thin wires can make full use of materials, and the production process of thin wires is relatively simple and low in cost. For cables such as electromagnet power cables that require certain conductivity and mechanical properties, the use of twisted wires can flexibly meet various electrical performance requirements by selecting wires of different specifications and materials for twisting, while controlling production costs to a certain extent.

2   Function

2.1. Stable power transmission

The twisted wire structure can ensure that the power supply is stably transmitted during the operation of the electromagnet. Due to its good anti-electromagnetic interference ability, it can reduce the voltage and current fluctuations caused by electromagnetic interference, ensuring that the electromagnet can work normally according to the design requirements. For example, in high-precision electromagnetic control equipment, stable power transmission is essential for the precise control of electromagnets, and twisted wire power cords can effectively prevent the influence of external electromagnetic interference on the operation of electromagnets.

2.2  Extend the lifespan of the DC Solenoid

As mentioned above, the mechanical performance advantages of twisted wire power cords can maintain good performance in complex mechanical environments such as frequent bending and stretching, reducing the probability of damage to the power cord. For electromagnets, which may be in a dynamic working environment for a long time, this can greatly extend the service life of the power cord and reduce the maintenance cost and replacement frequency of the equipment.

3  Improve electromagnetic compatibility

 Effectively reduce the electromagnetic interference generated by the power cord itself, and can also resist external electromagnetic interference, so that the electromagnet and the surrounding electronic equipment can coexist harmoniously. This is particularly important in environments with dense electronic equipment, such as industrial automation production lines, electronic laboratories, etc., to avoid problems such as equipment failures and data errors caused by electromagnetic interference.

Part 2 :  The standards and aspects of twisted wires s  

2.1  Appearance requirements

• Surface finish: The surface of a single wire should be smooth, without obvious mechanical damage, oxidation discoloration, black spots, cracks, spots and inclusions, etc.13.
• Uniform color: For copper stranded conductors and tinned wire cores, the color should be uniform and bright, the tinning layer should be uniform, and there should be no leakage of plating13.
• Regular structure: The stranded wire should not have missing roots, fewer strands, broken strands, loose strands, overlapping strands, or folding. The eccentricity of the fan-shaped wire core should not exceed 10%13.

2.2 Dimension requirements

• Single wire size: The single wires that make up the stranded wire should be round and should not have obvious thinning. The thinning must be within the specified range13.
• Outer diameter of stranded wire: The outer diameter of the stranded wire should comply with the process requirements13.

2.3 Pitch and twist direction requirements

• Uniform pitch: The pitch should comply with the process requirements. The pitch ratio of multi-layer stranded wires gradually decreases from the inside to the outside, and the pitch of the same layer remains consistent13. · Clear twist direction: The twisted layers should be opposite. For example, ordinary stranded wires are usually twisted in a concentric circle, layer by layer, and the twist directions of adjacent layers are opposite.

2.4  Welding requirements

• Welding range: Except for hard copper conductors for overhead insulated wires, other copper conductors are allowed to be welded in single wires or strands, but whole core welding is usually not allowed 13.
• Welding head quality: The welding head should be polished and filed. The diameter of the welding head should not exceed 0.2mm of the nominal diameter. The spacing between welding heads in the same or adjacent layers should not be less than 300mm 13.

2.5  Electrical performance requirements

• DC resistance: The structure and composition of the stranded wire and the DC resistance value of the finished product should comply with the provisions of GB/T 3956-1997 "Cable Conductors" 13.
• Electromagnetic compatibility: It is necessary to meet relevant electromagnetic compatibility standards, such as limiting the electromagnetic interference generated by the power line and improving the ability of the power line to resist external electromagnetic interference.

2.6  Materials and other requirements

• Material quality: Conductor materials should comply with relevant standards. For example, when using annealed copper or annealed copper-plated materials, they must comply with ASTM B3, B33 or B189 standards6.
• Packing requirements: The conductor cores of the coils should be neat and flat, without waist drum shape or overlap of cores.