1 Packaging should look for which factory is producing what brand, to prevent the purchase of Shanzhaigou (such as the well-known "Zhongze Yongtong" wire in Hangzhou, the cottage is called "China policy" "Yongtong policy", as well as the name of the plant Brand name etc). Whether there is a “CCC†and a production license number for Chinese national mandatory product certification on the wire packaging label; see if there is a quality system certification; see whether the certificate is standardized; see if there is a factory name, site, or chapter , date of production; see if there are trademarks, specifications, voltages, etc. printed on the wires. 
2 length and thickness of a coil of 100m, the national standard length error is not more than 0.5%, which is not less than 99.5m. No cross-sectional national standard data was found. The commonly used cross-sectional area is 1.5mm?2; the plastic insulated single-stranded copper core wire has a weight of 1.8-1.9kg per 100m; 2.5mm?2; 3.1kg. Poor quality wires have insufficient weight or length, or too much copper core impurities. 
3 Eccentricity Cut a section of insulation to see if the core is in the middle of the insulation. Not centered is due to the fact that the process is not high and causes the eccentric phenomenon. Once the power is used, the thinner side is likely to be broken by the current. 
4 Insulation layer It is advisable to use a wire head to bend repeatedly by hand. Any product with soft hand feeling, good anti-fatigue strength, high elasticity of plastic or rubber feel, and no crack on the wire insulation is superior. The outer plastic skin of the wire should be brilliance and texture, and there should be no open flame when lit with a lighter. Wire purchase
what makes most electric power tools "different" from one another depends on how the physical energy is used, or its application. The process of making physical energy with electrical energy is very similar and where most performance issues occur. for most power tools, and happens to be where most maintenance is required
Although there is a lot more to be said about how electric motors work, no one has to be an electrical engineer to understand a motor's basic parts. And understanding what goes on inside of a power tool makes diagnosing problems easier.
If the problem can be pinned down early, then the tool is just a part and a quick repair away from being almost like new again. Even some of the repairs and maintenance required for electric power tools are fast and easy to do.
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